• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.1
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• pp.1-5
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• 2015

For the special usage, the effort of developing AlN single crystals has been very hot in the world. The AlN-base UV LEDs are used on the field of sterilization, purification, curing and analyzing, which can advance human's living and medical processes etc.. AlN single crystals were grown by the PVT (Physical vapor transport) method. On the growing process, carbon crucibles with three different types such as normal size, taller than normal and wider than normal were used for comparison. The processing temperature was in the range of $1900{\sim}2100^{\circ}C$ and ambient pressure was 200~1 Torr. When the taller crucible was used, the sublimation mass was greater than normal dimension one but the best condition of growth changes widely. However the wider one gave much sublimation mass and growing condition was more stable than normal dimension. On limited growing furnace system, the changes of crucible dimension of PVT method provide the change of best condition for growth rate, as-grown crystal quality and growth condition stability.

• KSBB Journal
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• v.11 no.3
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• pp.303-310
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• 1996

The marine microalga Isochrysis galbana Parke was studied to optimize its growth conditions in flask culture. Important medium components studied include nitrogen source, buffer, trace elements and vitamins. Environmental conditions include pH, temperature, light intensity, mixing extent and working volume. The medium prepared from natural sea-waters gave a higher final cell density than the medium prepared from synthetic sea-water Nitrate was a better source than ammonium. In the range of 0.4∼2mM, the final cell density was proportional to the initial nitrate concentration and the cell yield was estimated to be 8.5g dry cell wt/g N. For phosphate, optimal growth was observed in 0.1∼1.0mM but a considerable variation in pH was resulted. The addition of Tris at 5mM or 7mM could stabilize the medium pH, but this significantly reduced both growth rate and final cell density, The effect of trace elements and vitamins was negligible. Optimal temperature and initial pH were $20^{\circ}C$ and 8. When the intensity of incident light was varied in the range of 400∼2100 lux, the growth rate increased from 10mL to 70mL, the final cell density decreased although the initial growth rate did not change. Optimal agitation speed was 100rpm when working volume was 30mL. With optimal conditions, the maximum specific growth rate obtained was 0.021hr-1 and the final cell density was 1.1g/L.

• Korean Journal of Food Science and Technology
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• v.21 no.3
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• pp.399-403
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• 1989

Studies were made to optimize the meida composition and cultural conditions for the mycelial growth of Agrocybe cylindracea. Media composition for optimal growth was found to be starch 20.0g/l, bacto-soytone 4.0g/l. The media supplemented with $KH_2PO_4\;0.46g/l,\;K_2HPO_4\;1.0g/l,\;MgSO_47H_2O\;0.5g/l$ supported mycelial growth better than the media without mineral salts. Optimum temperature and pH for the growth was $28^{\circ}C$, and 6.0 respectively. Temperature range for the mycelial growth appeared to be $10-35^{\circ}C$ and the mycelium evidently lost the vitality at $40^{\circ}C$.

• KSBB Journal
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• v.11 no.2
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• pp.254-261
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• 1996

Attenuated varicella-zoster virus (VZV) was propagated in human lung fibroblast (HLF) cells Among media tested in this work, DMEM was the best medium for the growth of HLF cells. Because HLF was a normal finite cell line, cell growth late was dependent on the age of HLF cells. When the population doubling level (PDL) was higher than 46, apoptosis of HLF cells started and cell growth rate decreased. The optimum temperature for the cell growth and virus propagation in the T-flask culture was $37^{\circ}C$. In a microcarrier culture system in which Cytodex-3 was used for the VZV propagation in spinner vessels, the yield of plaque forming cells was lower than that in the T-flask culture. The relatively high shear environment near microcarriers was thought to cause the low yield of VZV in the microcarrier culture system.

• Journal of Life Science
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• v.13 no.5
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• pp.559-568
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• 2003

The aim of present study is to investigated on the development of the functional doenjang possessing antioxidative and fibrinolytic activity. A strain, BH-23 showing antioxidative and fibrinolytic activity was isolated from traditionally doenjang, and then identified as Bacillus subtilis based on moophological, physiological, and biochemical characteristics, and named as Bacillus subtilis BH-23. The optimal pH level and temperature conditions were 5.0 and $40^{\circ}C$, NaCl concentration was grown well at 15% Antioxidative and fibrinolytic activity of Bacillus subtilis BH-23 was accoidance with growth conditions of the original state. By comparising with traditionally commercialized doenjang, it is prepared with Bacillus subtilis BH-23. The final results evaluated with positive elements rised above the surface such as color, taste and flavor without ammonia. Therefore, it is safe to assume, doenjang has strong market value in the food industry.

• Applied Chemistry for Engineering
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• v.21 no.6
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• pp.659-663
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• 2010

Microalgae has been seen all over the seawater and several species are used for human food. Specially, Nannochloropsis oculata, a photosynthetic microalgae, has been focused for a vast array of valuable nutritious compounds. In order to find high mass Nannochloropsis oculata culture conditions, some of important growth factors of pH, temperature, culture media, and $CO_2$ effect were tested. The optimal growth condition was found to be as follows : 3% artificial seawater, initial pH 8.5, and temperature $25^{\circ}C$. The alga mass and chlorophyll content were dramatically increased by applying 5% flue $CO_2$ gas (1.50 g/L algae in a continuous $CO_2$ flue; 0.76 g/L alga without $CO_2$). It was shown that the chlorophyll biosynthesis was also closely associated with alga growth.

• Journal of the Korean GEO-environmental Society
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• v.13 no.10
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• pp.63-68
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• 2012

This study was performed to determine optimum conditions of batch type cultivation of Isochrysis galbana cultivated under various wavelengths of light emitting dioes (LEDs). Among LEDs used in the cultivation, white LED was found to be the most effective light source, and light intensity of 3,000Lux resulted in the most effective for the cultivation of Isochyrysis galbana. Comparison with common light source, fluorescent light, showed less effective than that with white LED. Four different air flow rates were tested to overcome shading effects due to denser cell concentration in the solution. In results, cell growth rates and maximum cell concentrations were similar regardless of air flow rates. Three times greater cell concentrations, however, were observed when air was applied.

• Korean Journal of Materials Research
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• v.6 no.11
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• pp.1113-1120
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• 1996

다이아몬드 박막을 이용한 반도체소자를 실현시키기 위해서는 다이아몬드가 아닌 다른 재료의 기판위에 대면적에 걸쳐 다이아몬드막을 에피텍셜 성장시키는 것이 필수적이다. 그러나 이 분야의 연구는 아직 초보상태로 그 목표가 실현되지 못하고 있다. 본 논문에서는 저압의 ECR 마이크로파 플라즈마 CVD에 의하여 대면적의 Si(100)기판상에 방향성을 갖는 다이아몬드막을 성공적으로 성장시킨 결과를 보고자한다. 지금까지 얻어진 최적 핵생성 공정조건은 다음과 같다 : 반응압력 10Pa, 기판온도 80$0^{\circ}C$(마이크로파 전력이 3kW일 때), 원료가스 CH4/He 계로 농도비 3%/97%, 가스총유량 100sccm, 바이어스 전압 + 30V, 마이크로파 전력(microwave power)4kW, 바이어스 처리 시간 10분간이며, 성장단계에서의 증착공정 조건은 기판온도 80$0^{\circ}C$, 원료가스 CH4/CO2/H2계로 농도비 5%/15%/85%, 가스 총유량 1000sccm, 바이어스 전압 +30V, 마이크로파 전력 5kW, 성막시간 2시간으로 일정하게 유지하였다. 이 조건하에서 기판 면적 3x4$\textrm{cm}^2$의 대면적에 대해서 약 2x109cm-2의핵생성 밀도를 균일하게 재현성있게 얻었다. 원료가스로 CH4/H2를 사용한 경우보다 CH4/H2를 사용할 경우에 라디칼밀도의 증가에 의하여 더 높은 핵생성밀도를 얻을 수 있었다. 또한 저압의 ECR플라즈마 CVD의 경우에는 양의 바이어스전압이 막의 손상이 없어 다이아몬드 핵생성에 더 적합하였다.

• Journal of the Korean Vacuum Society
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• v.4 no.1
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• pp.40-45
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• 1995

직경 2인치의 YBa2Cu3O7-y 타겟을 사용하여 높은 스퍼터링 기체 압력 하에서 off-axis DC-마그네트론 스퍼터링 방법으로 MgO(100) 단결정 기판 위에 YBa2Cu3O7-y 박막을 c축 방향으로 in-냐셔 성장시킬 때 기판의 접지 여부와 인가전류의 양이 박막 성장에 미치는 여향을 연구하였다. 그 결과 접지 여부는 박막의 초전도 변환온도, 전기수송 특성, 결정 구조적 특성에는 영향을 거의 주지 않는 반면 표면상태에는 상당한 영향을 미치며, 인가전류의 양은 초전도 특성에 많은 영향을 미침을 발견하였다. 기판온도 $670^{\circ}C$, 스퍼터링 기체압력 300mTorr, 아르곤 대 산소 분압비 5:1의 조건에서 인가전류의 최적량은 300-500 mA이었으며 평균 박막 성장속도는 $0.11-0.14AA$/s로 매우 낮았다. 기판의 접지 효과와 낮은 성장속도의 원인에 대해 고찰해 본다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.179-179
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• 2016

희토류계 영구자석은 높은 보자력과 잔류 자화을 가지고 있어 자기기록저장매체, MEMS(엑츄에이터), 센서 등의 응용 분야에 적용시키기 위해 다양한 연구들이 진행되고 있다. 하지만 희토류계 원소의 수급 및 가격의 문제점으로 친환경자석으로의 전환 및 희토류나 중희토류를 사용하지 않는 비희토류계 영구자석을 개발하는 연구에 대한 필요성이 대두되고 있다. 이 중 Fe-N 계 자성 물질인 $Fe_{16}N_2$는 포화 자화 값이 현재까지의 자성물질 중 가장 높은 값(240emu/g)을 나타내며 상대적으로 높은 결정자기이방성 상수를 가지고 있어 비희토류계 영구자석 물질 중 하나로 주목받고 있다. 본 연구에서는 $Fe_{16}N_2$ 박막을 얻기 위해 DC Magnetron Sputtering 방법을 이용하여 Si wafer 위에 박막을 증착하고 증착공정 조건 중 질소 유량 및 Sputtering Power를 변수로 따른 박막의 성장, 조직변화, 자성 특성을 관찰을 통해 최적의 공정 조건을 찾고자 하였다. $N_2$ 가스 유량 변화에 따른 박막의 성장 속도는 거의 변화가 없었으며 $N_2$ 가스 유량의 증가에 따라 박막 내 Fe의 함유량은 감소하였다. 모든 공정 조건에서 $Fe_3N$, $Fe_4N$, $Fe_{16}N_2$ 상들이 섞여 성장하였으며 XRD를 통한 상분석과 더불어 VSM을 통한 자성 특성을 분석해본 결과 $Fe_{16}N_2$의 분율이 가장 높게 성장된 공정 조건은 Power는 200W, $N_2$ 가스 유량은 20sccm이었으며 이 조건에서 2.45T의 포화 자화 값과 1.4T의 잔류 자화 값을 얻을 수 있었다.