• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.134-140
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• 2007

Nonlinear parabolized stability equations for compressible flow in general curvilinear coordinate system are derived to deal with a broad range of transition prediction problems on complex geometry. A highly accurate finite difference PSE code has been developed using an implicit marching procedure. Blasius flow is tested. The results of the present computation show good agreement with DNS data. Nonlinear interaction can make the T-S fundamental wave more unstable and the onset of its amplitude decay is shifted downstream relative to linear case. For nonlinear calculations, rather small difference in initial amplitude can produce large change during nonlinear region. Compressible secondary instability at Mach number 1.6 is also simulated and showed that 1.1% initial amplitude for primary mode is enough to trigger the secondary growth.

• 열처리공학회지
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• 제23권6호
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• pp.309-314
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• 2010

Microstructures and grain growth behaviors at elevated temperatures have been investigated for extruded Mg-2%Zn and Mg-2%Zn-0.3%Zr alloys, in order to clarify the role of Zr in grain stability of Mg-Zn alloy. The grain size of Zr-free alloy increased continuously with an increase in annealing temperature, when isochronally annealed for 60 min from 573 to 723K, while the grains of the Zr-containing alloy were relatively stable up to 723 K. The activation energies for grain growth ($E_g$) between 573 and 723 K were calculated as 77.8 and 118.6 kJ/mole for the Mg-2%Zn and Mg-2%Zn-0.3%Zr alloys, respectively, which indicates that grains in the Zr-added alloy possess higher thermal stabilities at elevated temperatures. TEM observations on the annealed Mg-2%Zn and Mg-2%Zn-0.3%Zr alloys revealed that enhanced grain stability resulting from Zr addition into Mg-Zn alloy would be ascribed to the restriction of grain growth by stable Zn-Zr nano-precipitates distributed in the microstructure.

• International Journal of Korean Welding Society
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• 제2권1호
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• pp.25-28
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• 2002

In the coarse grain HAZ adjacent to the fusion line, most of the TiN particles in conventional Ti added steel are dissolved and austenite grain growth is easily occurred during welding process. To avoid this difficulty, thermal stability of TiN particle is improved by increasing the nitrogen content in steel. In this study, the effect of hlgh nitrogen TiN particle on preventing austenite grain growth in HAZ was investigated. Increased thermal stability of TiN particle is helpful for preventing the austenite grain growth by pinning effect. High nitrogen TiN particle in simulated HAZ were not dissolved even at high temperature such as 1400'E and prevented the austenite grain growth in simulated HAZ. Owing to small austenite grain size in HAZ the width of coarse grain HAZ in high nitrogen TiN steel was decreased to 1/10 of conventional TiN steel. Even high heat input welding, the microstructure of coarse grain HAZ consisted of fine polygonal ferrite and pearlite and toughness of coarse grain HAZ was significantly improved.

• 한국미생물·생명공학회지
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• 제24권5호
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• pp.619-623
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• 1996

Some physical and physiological properties of di-D-fructofuranose dianhydrideIII (DFAIII), as a new sweetener, were investigated via in vitro experiments. The disaccharide was prepared by decomposing inulin with inulin fructotransferase (depolymerizing) from Arthrobacter sp. A-6. DFAIII had more excellent heat and acid stability than sucrose. This was one of the most desirable properties especially for the oligomer types of sweetener. DFAIII showed the least pH drop in the Streptococcus mutans culture, compared with the other saccharides examined. This indicates that the sugar will be fairly effective for preventing dental caries. The saccharide also had a selective Bifidus growth-promoting effect in PYF medium. Whereas, E. coli did not show growth promotion in the DFAIII-containing medium. In the co-culture of Bifidus longum and E. coli in the BL medium, Bifidus longum had a selective growth while the growth of E. coli appeared rather to be inhibited.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1996년도 제11차 KACG 학술발표회 Crystalline Particle Symposium (CPS)
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• pp.109-128
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• 1996

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.481-486
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• 2001

The hydrodynamic instability of the three-dimensional boundary layer on a rotating disk introduces a periodic modulation of the mean flow in the form of stationary cross flow vortices. Detailed numerical values of the growth rates, neutral curves and other characteristics have been calculated for the Type II-instabilities. Presented are the neutral stability results concerning the two instability modes by solving new linear stability equations reformulated not only by considering whole convective terms but by correcting some errors in the previous stability equations. The present stability results are agree with the previously known ones within reasonable limit. The spatial amplification contours have been calculated for the moving disturbance wave, whose azimuth angle is between $\varepsilon=-10^{\circ}$ and $-20^{\circ}$. The transition flow of the moving disturbance wave will be developed at $\varepsilon=-15^{\circ}$ and Re=352 corresponding at the growth rates n = 5.8 from the spatial amplification contours.

• 약학회지
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• 제43권6호
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• pp.793-797
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• 1999

Salmonella typhi Ty21a is an attenuated strain of S. typhimurium and used for oral typhoid vaccine. In an attempt to increase the stability of Ty21a manufacturing typhoid vaccine, we studied about the stability of freeze-dried Th21a including additives at various temperature conditions. In order to investigate the freeze-drying rate of Ty21a according to various absorbance, we lyophilized Ty21a by using 8% sucrose as a stabilizer. The optimal freeze-drying rate of Ty21a was appeared when OD (optical density) value of the growth was between 2.5 and 3.0. To investigate the stability of Ty21a at various temperature, the viability was measured after storaging the freeze-dried Ty21a at the room temperature, cold and freezing condition for 1 week. The viability of Ty21a in cold and freezing storage condition was 5 times more stable than in room temperature. To search the most stable additives for the freeze-dried Ty21a, the viability of Ty21a including additives at the various storage condition was estimated. Mannitol and loctose were the most stable additives. Theses results suggest that the OD value of Ty21a growth, low temperature, mannitol and lactose are important factors for the optimal freeze-drying rate, the stable storage and the most stable additives, respectively.

• 한국미생물·생명공학회지
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• 제16권4호
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• pp.327-333
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• 1988

대장균을 이용한 재조합 인체 인터루킨-2(IL_2) 생산의 최적화를 위하여 발효조건이 세포성장과 IL-2의 생산 및 재조합 세포의 안정성 등에 미치는 영향을 조사하였다. 복합배지의 경우에는 yeast extract, peptone, corn steep liquor 등이 재조합 세포성장에 좋은 효과를 나타내었다. 재조합 세포의 안정성은 IL-2 발현 억제 조건(3$0^{\circ}C$)에서는 안정하게 유지되었으나 IL-2 생산조건(42$^{\circ}C$)에서는 selection pressure를 주었을 때조차도 현격하게 감소함을 알 수 있었다. 한편 배양배지에 항생제를 첨가한 경우에도 안정성 유지에는 별로 도움이 되지 못하고 세포성장만 억제됨을 알 수 있었다. 유전자의 발현은 대수 증식 중기에서 유도했을 때가 IL-2 생산에 가장 좋은 것으로 나타났으며 IL-2 생산은 세포성장과 플라스미르내의 다른 유전자들의 발현을 상당히 저해시킴을 알 수 있었다.

• Fisheries and Aquatic Sciences
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• 제27권5호
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• pp.265-275
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• 2024

The success of establishing the Indonesian growing fast hybrid carp, namely "Permata", on a controlled environmental test must be followed up with a large-scale test. This study aims to evaluate the phenotypic performance of the Permata hybrid carp in multi-locations with different cultivation systems. The test sites consisted of floating net cages, running-water ponds, semi-concrete ponds, earthen ponds, fully concrete ponds, and static net cages. For 90 days, fish were fed commercial pellets with a 28%-30% protein content. At the end of the test, all fish were harvested and counted. Data on length, weight, survival rate, and harvested biomass were used to analyze the effect of genotype, environment, and their interaction on the phenotypic performance. The growth based on final weight is used to analyze the stability performance in each test location. The results showed that the length and weight of common carp were significantly affected by genotype and the environment, but not by the interaction of both. The genotype, environment, and the interaction of both factors affected common carp's survival and harvested biomass. Common carp reared in floating net cages generally had the best performance, while carp reared in fully concrete tanks and static net cages had the lowest. The growth stability analysis showed that the common carp in this study were unstable genotypes but have a broad adaptability in term of different environments.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.376-376
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• 2012

Semiconductor nanowires (NWs) are future building block for nano-scale devices. Especially, Ge NWs are fascinated material due to the high electrical conductivity with high carrier mobility. It is strong candidate material for post-CMOS technology. However, thermal stability of Ge NWs are poor than conventional semiconductor material such as Si. Especially, when it reduced size as small as nano-scale it will be melted around CMOS process temperature due to the melting point depression. Recently, Graphene have been intensively interested since it has high carrier mobility with single atomic thickness. In addition, it is chemically very stable due to the $sp^2$ hybridization. Graphene films shows good protecting layer for oxidation resistance and corrosion resistance of metal surface using its chemical properties. Recently, we successfully demonstrated CVD growth of monolayer graphene using Ge catalyst. Using our growth method, we synthesized Ge/graphene core/shell (Ge@G) NW and conducted it for highly thermal stability required devices. We confirm the existence of graphene shell and morphology of NWs using SEM, TEM and Raman spectra. SEM and TEM images clearly show very thin graphene shell. We annealed NWs in vacuum at high temperature. Our results indicated that surface melting phenomena of Ge NWs due to the high surface energy from curvature of NWs start around $550^{\circ}C$ which is $270^{\circ}C$ lower than bulk melting point. When we increases annealing temperature, tip of Ge NWs start to make sphere shape in order to reduce its surface energy. On the contrary, Ge@G NWs prevent surface melting of Ge NWs and no Ge spheres generated. Furthermore, we fabricated filed emission devices using pure Ge NWs and Ge@G NWs. Compare with pure Ge NWs, graphene protected Ge NWs show enhancement of reliability. This growth approach serves a thermal stability enhancement of semiconductor NWs.