• Toxicological Research
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• 제11권2호
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• pp.175-180
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• 1995

We found that bufalln, one of the prominent components of the bufadlenolides in the Chinese medicine chan'su, has the potent inhibitory effects on growth and proliferation of the cultured bovine aortlc endothelial (BAE) and human umbilical vein endothelial (HUVE) cells. All naturally-occuring bufadienolides used in this study inhibited the cell growth in a dose-dependent manner. Particularly, bufalin among the bufadienolides showed the strongest inhibitory activity for the cell growth. The order of growth inhibition by bufadienolides on BAE cells was as follows: bufalin > gamabufotalln > bufotalln > cinobufagin > cinobufotalin > resibufogenin. The $IC_50$ values (50% inhibition of cell growth) of bufalin as determined by XTT assay were the range of 1-10 nM in BAE and HUVE cells. Bufalin exhibited a higher sensitivity towards cultured bovine aortic endothelial cells than human umbilical vein endothelial cells.

• KSBB Journal
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• 제6권1호
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• pp.91-98
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• 1991

The media compositions and culture conditions were optimized for mycelial growth of Coriolus versicolor and Lentinus edodes. Media composition for optimal growth of Coriolus versicolor was 2.0% glucose 0.4% peptone and 0.6% yeast extract. Media composition for optimal growth of Lenttnus edodes was 2.0% glucose 2.0% starch 0.4% bacto-soytone and 0.6% yeast extract. The media supplemented with KH2PO4, 0.046% KH2PO4 0.1% and MgSO4, .7H2O 0.05% supported better mycelial growth than the media without mineral salts. The optimum temperature for mycelial growth ranged from $25^{\circ}C$-28$^{\circ}C$. The optimum pH range for mycelial growth of Coriolus versicolor was 5.2~5.6 while that of Lentinus edodes appeared to be 5.75.

• 한국결정성장학회지
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• 제13권4호
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• pp.187-198
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• 2003

Zinc selenide (ZnSe) single crystals hold promise for many electro-optics, acousto-optic and green laser generation applications. This material is prepared in closed ampoules by the physical vapor transport (PVT) growth method based on the dissociative sublimation. We investigate the effects of diffusive-convection on the crystal growth rate of ZnSe with a low vapor pressure system in a horizontal configuration. Our results show that for the ratios of partial pressures, s=0.2 and 2.9, the growth rate increases with the Peclet number and the temperature differences between the source and crystal. As the ratio of partial pressures approaches the stoichiometric value of 2, the rate increases. The mass fluk based on one dimensional (1D model) flow for low vapor pressure system fall within the range of the predictions (2D model) obtained by solving the coupled set of conservation equations, which indicates the flow fields would be advective-diffusive. Therefore, the rate and the flow fields are independent of gravity acceleration levels.

• 한국정밀공학회지
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• 제16권2호통권95호
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• pp.225-233
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• 1999

This paper describes a versatile finite element technique which has been used to investigate of wide range of structural defects of practical importance. The procedure automatically remeshes the three-dimensional finite element model during the stages of crack growth. Problems analyzed to date include the surface cracks in leak-before-break situations, the development of quarter-elliptical corner defects, planar semi-elliptical surface defects and the fatigue growth of defects.

• 한국자동차공학회논문집
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• 제10권6호
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• pp.133-141
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• 2002

This paper describes a versatile finite element technique which has been used to investigate wide range of structural defects of practical importance. The procedure automatically remeshes the three-dimensional finite element model during the stages of crack growth. Problems include the surface cracks in leak-before-break situations, the shape development of multiple surface defects.

• Journal of Ginseng Research
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• 제10권2호
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• pp.159-166
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• 1986

Effects of plant growth regulators on the germination of ginseng (Panax ginseng C.A. Meyer) seeds were investigated. Ginseng seeds germinated more vigorously in the treatments of kinetin and BA, and the promoting effect of kinetic on the germination and the growth of rootlet enhanced in low temperature ($10^{\circ}C$). However, GA did not promote the germination of dehiscent seed. The optimum temperature for germination of dehiscent seed was $10^{\circ}C$ and the range of effective concentration of kinetin for germination was 50 to 100 ppm.

• 한국세라믹학회지
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• 제26권4호
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• pp.459-470
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• 1989

Single crystals of rare-earth iron garnets were grown from solutions of molten lead oxide, lead fluoride, baric oxide, iron oxide, and the oxides of yttrium, samarium orgadolinium. The crystals were grown by slow cooling technique. A convenient composition was 41.8mol% PbO, 20.59mol% PbF2, 8.23mol% B2O3, 20.00mol% Fe2O3 and 10.00mol% R2O3 where R is Y, Sm or Gd. For this experiment, platinum crucibles of size 20, 30cc and a vertical siliconit tube furnace were used. The precipitation temperature of YIG was observed in the range of 115$0^{\circ}C$-112$0^{\circ}C$ and the optimum growth conditions in this experiment were determined. The nucleation rate was controlled by the holding time after the fast colling, the growth rate by the slow cooling conditiions. The form of the grown YIG crystals showed a combination of {110} and {211}, and the size of the crystals grown in this experiment was up to about 9mm under the conditions of holding time 16hour, cooling rate 2$^{\circ}C$/hr. and temperature range 115$0^{\circ}C$-90$0^{\circ}C$. The precipitatin temperature of SmIG was observed in the range of 105$0^{\circ}C$-98$0^{\circ}C$ and the size of the crystals grown in this experiment was up to about 5mm under the conditiions of holding time 16hours, cooling rate 2$^{\circ}C$/hr. and temperature range 100$0^{\circ}C$-80$0^{\circ}C$.

• 기술혁신학회지
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• 제11권1호
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• pp.72-90
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• 2008

기술혁신이 경제성장에 미치는 영향은 어떠한가? 이는 전통적으로 지식스톡을 반영하는 성장회계법에 의해 분석되었다. R&D에 대한 수익률 추정은 특허와 같은 R&D 산출이 지식축적에서 기인하는 것으로 파악한다. Griliches(1973)는 이를 위해 회귀분석 방법을 사용하였다. 본 연구에서는 기존 성장회계법에서의 추정방법과 달리 R&D 효율성을 나타내는 파라미터가 시간이 지남에 따라 변동(time-varying)하는 것을 허용하는 상태공간 모형(state-space model)을 통해 한국경제의 R&D 효율성(fertility)을 추정하였다. R&D 스톡의 생산성에 대한 탄력성은 $0.120{\sim}0.135$ 정도로 추정되었다.

• Journal of Welding and Joining
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• 제35권1호
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• pp.34-42
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• 2017

This paper presents a comparative study of the AC and MFDC resistance spot welding process with consideration of sheet thickness. The previous studies have confirmed that there is difference in the optimum welding current and expulsion current with AC and MFDC. The aim of this study was revealing the effect of sheet thickness on weldable current range and expulsion behavior for AC and MFDC welding processes. The optimum welding current of AC was lower (1.6 kA) than MFDC welding process in 0.8 mm sheet thickness. Early nugget growth being caused by the peak current of AC developed weld interface deformation, which resulted in suppressing the growth of corona bond and occurrence of low current expulsion. The resistance spot welding for thicker sheet (1.4 mm) required lower current of 0.6 kA for the expulsion on the MFDC welding process. The growth of contact diameter (size of corona bond) and button diameter was linear up to the expulsion current with MFDC welding process. Therefore, more attention is required when the AC and MFDC resistance spot welding process is applied for different thickness of steel sheet combination for automotive application.

• 대한기계학회논문집A
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• 제23권7호
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• pp.1139-1146
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• 1999

Reliability analysis of structures based on fracture mechanics requires knowledge on statistical characteristics of the parameter C and m in the fatigue crack growth law, $da/dN=C({\Delta}K)^m$. The purpose of the present study is to investigate if it is possible to predict fatigue crack growth rate by only the fluctuation of the parameter C. In this study, Paris-Erdogan law is adopted, where the author treat the parameter C as random and m as constant. The fluctuation of crack growth rate is assumed only due to the parameter C. The growth resistance coefficient of material to fatigue crack growth (Z=1/C) was treated as a spatial stochastic process, which varies randomly on the crack path. The theoretical crack growth rates at various stress intensity factor range are discussed. Constant ${\Delta}K$ fatigue crack growth tests were performed on the structural steel, SM45C. The experimental data were analyzed to determine the autocorrelation function and Weibull distributions of the fatigue crack growth resistance. And also, the effect of the parameter m of Paris' law due to variation of fatigue crack growth resistance was discussed.