• 대한기계학회논문집A
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• 제24권11호
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• pp.2749-2761
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• 2000

Densification, grain growth, and phase transformation of nanocrystalline ceramic powder were investigated under pressureless sintering, sinter forging, and hot pressing. A constitutive model for densification of nanocrystalline ceramic powder was proposed and implemented into a finite element program (ABAQUS). A grain growth model was also proposed by including the effect of applied stress on grain growth when phase transformation occurs. Finite element results by using the proposed models well predicted densification behavior, deformation, and grain growth of nanocrystalline titania powder during pressureless sintering, sinter forging, and hot pressing. Finite element results by using the proposed model also well predicted experimental data in the literature for densification behavior of nanocrystalline zirconia powder during pressureless sintering and sinter forging.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.363-368
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• 2000

Densification, grain growth, and phase transformation of nanocrystalline ceramic powder were investigated under pressureless sintering, sinter forging, and hot pressing. A constitutive model for densification of nanocrystalline ceramic powder was proposed and implemented into a finite element program (ABAQUS). A grain growth model was also proposed by including the effect of applied stress on grain growth when phase transformation occurs. Finite element results by using the proposed models well predicted densification behavior, deformation, and grain growth of nanocrystalline titania powder during pressureless sintering, sinter forging, and hot pressing.

• 한국식품영양학회지
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• 제12권1호
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• pp.50-54
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• 1999

Effect of galactooligosaccharides produced by the $\beta$-galactosidase from Aapwefillua niger CAD 1 on the growth of Bifidobacterium infantis KCTC 3127 Bifidobacterium longum KCTC 3128 and Bifidobacterium bif-idum ATCC 11863 were investigated. Bifidbacterium infantis Bifidobacterium longum and Bifidobacterium bif-idum were in the logarithmic growth phase after 6hr incubation at 37$^{\circ}C$. Bifidobacterium infantis was in the stationary phase after 24hr incubation at 37$^{\circ}C$. The growth rate of B. bifidum containing galactooligo-saccharides and raffinose in MRS broth increased up to 18%, 8% and 7% compared to glucose galac-tose and lactose during 48hr incubation. The growth rate of B. infantis and B. longum contatining galacto-oligosaccharides and raffinose in MRS broth increased up to both 6% and 8% and both 13% and 10% compared to glucose and galactose during 48hr incubation.

• 한국연초학회지
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• 제2권2호
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• pp.44-50
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• 1980

황색종 잎담배의 생장분석에서 얻어진 결과는 다음과 같다. 1. 개량말칭의 생장곡선은 대수변환하여 2차 회귀식에, 기타 작부는 Gomuertz방정식과 유사하였다. 2. 건물량에 있어서 최대생장기의 시점은 개량말칭의 경우에 이식후 50일경, 타 작부는40일경이고 최대생장기간은 모두 25일 였다. 3 건물량에 있어서 최대생장기의 생장속도는 개량, 일반, 나지작의 순서로 감소하였다. 4. 파기가 늦을수록 최대생장기 동안의 생장량은 증가했다. 5. 엽면적의 최대생장기간은 건물중에 비하여 약2일 단축되고 5일 정도 빠르게 나타났다.

• Journal of Microbiology and Biotechnology
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• 제13권4호
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• pp.560-563
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• 2003

During our previous studies on the relationship between nutrient requirements of S. hygroscopicus C9 and rapamycin biosynthesis, we developed chemically-defined media containing among other nutrients, aspartic acid, arginine, histidine, or ammonium sulfate. However, these media (“Cheng et al. medium” and “Lee et al. medium”) showed very slow growth characterized by a very long lag phase of growth. In an attempt to develop a chemically-defined or semi-defined medium to support more rapid growth and increased cell production, we have carried out studies to shorten the lag phase. Of the various additives tested, vitamin-free casein acid hydrolysate was the most significant by shortening the lag phase by 2-3 days. Mixtures of amino acids failed to replace casein acid hydrolysate. The active principle passed through an ultrafilter with a molecular weight cutoff of 1,000 and thus may be a peptide. The present work has yielded a semi-defined medium which should be useful for further growth studies on S. hygroscopicus C9.

• The Korean Journal of Physiology and Pharmacology
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• 제7권2호
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• pp.91-96
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• 2003

In Korean folk medicine, several herbs, Glycyrrhizae Radix, Persicae Semen, Salviae Radix, Angelicae Gigantis Radix, Zanthoxyli Fructus, Ginseng Radix Alba, Cnidii Rhizoma, and Carthami Flos, are known to enhance blood circulation and have wound healing or anti-inflammatory effects. These pharmacological actions prompted us to investigate whether these herbs might stimulate hair growth. Thus, using a mixture of their extracts called SPELA 707, we investigated their effects and found that SPELA 707 possessed significant hair cycle converting activity from the telogen phase to the anagen phase in C3H mice. Furthermore, we found that SPELA 707 enhanced the hair density in subjects with hair loss and also promoted the conversion of hair into the anagen phase in subjects with androgenetic alopecia. In addition, hair growth promotion effect of SPELA 707 occurred through inhibition of steroid $5{\alpha}$-reductase activity, which is known to block hair growth. Taken together, these results suggest that SPELA 707 has a potential to be used for the treatment of hair loss.

• 한국표면공학회지
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• 제24권1호
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• pp.1-17
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• 1991

Understanding of the detailed reaction mechanisms during MOVPE and ALE is essential to further improve the properties of the grown crystals and the controllability of the growth parameters. The unified models for the detailed reaction paths are not available at this stage. The study, however, has been advanced to the extent that consensus on some of the reaction paths can be drawn from the scattered data. Metalakyls such as TMGa and TMIn seem to nearly fully decompose in the gas phase through homogeneous reaction at the typical MOVPE growth temperature. Hydrides such as AsH3 and PH3, on the contrary. seem to decompose heterogeneously onthe substrate surfaces as well as homogeneously in the gas phase. However, at lower temperatures, where ALE crystals are typically grown, the growth process is strongly dependent on the surface reactions. It seems that steric hindrance effects which the radicals reaching the substrate exhibit on the surface the growth rate a function of the metalalkyle supply durations. In addition, dydrogens released from hydrides seem to play an essential role in removing carbons leberated from the metalalkyls. High growth temperatures also seem to be effective in desorbing carbons from surface. The understanding of the reaction mechanisms was possible though diverse appraaches utilizing many ex-situ and in-situ diagnostic techniques and genuine experimental designs. It is the purpose of this paper to review and discuss many of these efforts and to draw some possible conclusions from them.

• 한국표면공학회지
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• 제24권1호
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• pp.1.1-1.1
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• 1991

Understanding of the detailed reaction mechanisms during MOVPE and ALE is essential to further improve the properties of the grown crystals and the controllability of the growth parameters. The unified models for the detailed reaction paths are not available at this stage. The study, however, has been advanced to the extent that consensus on some of the reaction paths can be drawn from the scattered data. Metalakyls such as TMGa and TMIn seem to nearly fully decompose in the gas phase through homogeneous reaction at the typical MOVPE growth temperature. Hydrides such as AsH3 and PH3, on the contrary. seem to decompose heterogeneously onthe substrate surfaces as well as homogeneously in the gas phase. However, at lower temperatures, where ALE crystals are typically grown, the growth process is strongly dependent on the surface reactions. It seems that steric hindrance effects which the radicals reaching the substrate exhibit on the surface the growth rate a function of the metalalkyle supply durations. In addition, dydrogens released from hydrides seem to play an essential role in removing carbons leberated from the metalalkyls. High growth temperatures also seem to be effective in desorbing carbons from surface. The understanding of the reaction mechanisms was possible though diverse appraaches utilizing many ex-situ and in-situ diagnostic techniques and genuine experimental designs. It is the purpose of this paper to review and discuss many of these efforts and to draw some possible conclusions from them.

• Journal of Welding and Joining
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• 제20권1호
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• pp.97-102
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• 2002

The growth kinetics of intermetallic compound layers formed between the eutectic Sn-3.5Ag solder and the Cu and Ni/Cu pad by solid stateisothermal aging were examined. The interfacial reaction between the eutectic Sn-3.5Ag solder and the Cu and Ni/Cu pad was investigated at 70, 120, 150, $170^{\circ}C$ for various times. The intermetallic compound layer was composed of two phase: $Cu_6Sn_5$(${\varepsilon}-phase$) adjacent to the solder and $Cu_6Sn_5$(${\varepsilon}-phase$) adjacent to the copper and on solder/Ni pad the intermetallic compound layer was $Ni_3Sn_4$. Because the values of time exponent(n) have approximately 0.5, the layer growth of the intermetallic compound was mainly controlled by volume diffusion over the temperature range studied. The apparent activation energy for layer growth of total Cu-Sn($Cu_6Sn_5 + Cu_6Sn$), $Cu_6Sn_5$, $Cu_3Sn$ and $Ni_3Sn_4$ intermetallic compound were 64.82kJ/mol, 48.53kJ/mol, 89.06kJ/mol and 71.08kJ/mol, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.214-217
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• 2004

숭화법을 이용한 탄화규소(Silicon carbide) 단결정 성장시 사용되는 원료의 상(phase)이 단결정 성장에 미치는 영향을 알아보기 위해 알파형 탄화규소 분말(${\alpha}-SiC$ powder)과 베타형 탄화규소 분말(${\beta}-SiC$ powder)을 각각 사용하였다. 알파형 탄화규소 분말을 사용한 경우에 단결정(single-crystal)을 성장할 수 있었으나, 베타형 탄화규소 분말을 사용하였을 때에는 다결정(poly-crystal)이 성장되었다. 다결정 형성요인에 관한 EPMA 분석결과, 베타형 탄화규소 분말의 탄소에 대한 실리콘의 원소조성비$(N_{Si}/N_C\;=\;1.57)$가 알파형 탄화규소 분말의 경우보다$(N_{Si}/N_C\;=\;0.81)$ 높음을 확인하였다. 따라서 흑연도가니(crucible) 내부의 실리콘 원자가 알파형 탄화규소 분말을 사용하는 경우보다 높은 과포화상태가 되어 종자정 표면에 미세한 실리콘 액적(droplet)이 중착되고 이것으로부터 일정하지 않은 방향성(random orientation)을 갖는 탄화규소 다결정(다양한 방향성을 갖는 다형 포함)이 성장한 것으로 실리콘과 탄소 원소에 대한 EPMA 지도(map) 결과를 통해 확인할 수 있었다.