• 한국결정성장학회지
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• 제16권6호
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• pp.240-243
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• 2006

본 연구에서는 수열법을 이용하여 저품질의 호주산 천연 사파이어에 대한 색상개선을 행하였다. 호주산 천연 사파이어의 색상 개선에 대한 최적의 수열처리 조건은 다음과 같다. 즉, 수열반응온도 $320{\sim}350^{\circ}C$, 반응시간: 3일, 수열용매: 2 M NaOH 수용액이다. 이와 같은 조건하에서 수열 처리한 후에 투명한 색상의 호주산 천연 사파이어가 얻어졌으며 천연 사파이어 가치 차트로 비교한 결과, commercial 등급이 $middle{\sim}top$ 등급으로 색상이 개선되었음을 확인하였다.

• 한국결정성장학회지
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• 제16권6호
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• pp.260-266
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• 2006

화학적 방법에 의해 액상에서 실버가 잘 분산된 Ag coated silica를 제조하고 이를 평가하였다. Ag coated silica를 제조하기 위한 치적조건은 알카리 용액에서 반응온도 $100^{\circ}C$, 반응시간 2시간, 실버 코팅양은 5 wt%였다. 제조된 Ag coated silica는 실버가 응집되지 않은 일정한 크기의 단분산 실버가 실리카 표면에 균일하게 코팅되었으며, 윈적외선 방사율 $0.916{\sim}0.918$ 및 항균력 99.9%를 나타내었다.

• 한국표면공학회지
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• 제41권4호
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• pp.174-179
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• 2008

Nanosize tungsten powder was synthesized by ultrasonic spray pyrolysis method through a solution containing ammonium metatungstate hydrate $[(NH_4)_6W_{12}O_{39}{\cdot}H_2O]$ and reduction treatment. It was expected the improvement of mechanical properties due to increasing surface free energy and surface activity. Starting solutions with each concentration, reaction temperature and reduction treatment were significantly influenced on the formation of tungsten size and phase. It was found that particle size was decreased with concentration of starting solution and surface tension were decreased. The particle size was increased at thermal decomposition temperature above $600^{\circ}C$ by neck growth of interparticles. Tungsten particles were formed by reduction reaction in atmosphere of hydrogen gas at the temperature above $700^{\circ}C$.

• Environmental Engineering Research
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• 제23권2호
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• pp.205-209
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• 2018

The spectral composition of light can affect the growth and biochemical composition of photosynthetic microalgae. This study examined the use of light filtering through a solution of soluble colored additives, a cost-effective method to alter the light spectrum, on the growth and lipid production of an oleaginous microalga, Nannochloropsis gaditana (N. gaditana). Cells were photoautotrophically cultivated under a white light emitting diode (LED) alone (control) or under a white LED that passed through a solution of red and yellow color additive (4:1 ratio) that blocked light below 600 nm. The specific growth rate was significantly greater under filtered light than white light ($0.2672d^{-1}$ vs. $0.1930d^{-1}$). Growth under filtered light also increased the fatty acid methyl ester (FAME) yield by 22.4% and FAME productivity by 80.0%, relative to the white light control. In addition, the content of saturated fatty acids was greater under filtered light, so the biodiesel products had better stability. These results show that passing white light through an inexpensive color filter can simultaneously enhance cellular growth and lipid productivity of N. gaditana. This approach of optimizing the light spectrum may be applicable to other species of microalgae.

• 한국산학기술학회논문지
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• 제21권4호
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• pp.20-25
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• 2020

나노과학과 나노기술의 발전에 따라 선택적 패턴 성장을 위한 기술이 주목을 받고 있다. 실리카(Silica) 나노입자는 바이오 라벨링, 바이오 이미징 및 바이오 센싱에 사용되고 있는 유망한 나노소재이다. 본 연구에서는 실리카 나노입자를 수정된 스토버 방법(Stöber Method)인 졸겔(Sol-Gel) 공정으로 합성하였다. 또한 기판의 표면을 미세접촉프린팅 기술로 발수 처리하여 실리카 나노입자를 선택적으로 패턴 성장시켰다. 합성된 실리카 나노입자의 크기와 선택적으로 패턴 성장된 실리카 나노입자의 표면형상을 전계방출 주사전자현미경(Field Emission Scanning Electron Microscopy, FE-SEM)으로 조사하였고, 기판의 표면 기능화에 따른 기판의 접촉각 특성을 조사하였다. 그 결과 OTS 용액으로 발수 처리된 기판에서는 실리카 나노입자를 스핀 코팅하였을 때, 실리카 나노입자를 관찰할 수 없었으나, KOH 용액으로 친수 처리된 기판에서는 실리카 나노입자가 잘 코팅되는 것을 확인하였다. 또한 미세접촉프린팅 기술로 발수 처리한 기판영역 외에서만 실리카 나노입자가 선택적으로 패턴 성장하는 것을 FE-SEM으로 확인하였다. 이러한 실리카 나노입자의 패턴성장 특성을 염료가 도핑 된 실리카 나노입자에 적용한다면, 실리카 나노입자의 패턴 성장 기술은 바이오 이미징 및 바이오 센싱 분야에 유용하게 활용될 것으로 기대된다.

• 한국농공학회지
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• 제36권3호
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• pp.113-121
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• 1994

Since it is difficult to expect the normal production of plants in greenhouses during hot summer season in Korea, certain provisions on the control of extreme environmental factors in summer should be considered for the year-round cultivation in greenhouses. This study was carried out to find a method to suppress the temperature rising of nutrient solution by cooling, which is able to contribute to the improvement of the plant growth environment in hydroponic greenhouse during hot summer season. A mechanical cooling system using the counter flow type with double pipe was developed for cooling the nutrient solution efficiently. Also the heat transfer characteristics of the system was analysed experimentally and theoretically, and compared with the existing cooling systems of nutrient solution. The cooling capacities of three different Systems, which used polyethylene tube in solution tank, stainless tube in solution tank, and the counter flow type with double pipe, were evaluated. The performance of each cooling system was about 41 %, 70% and 81 % of design cooling load in hydroponic greenhouse of 1 ,000m$^2$ on the conditions that the flow rate of ground water was 2m$^3$/hr and the temperature difference between two liquids was 10 ˚C According to the results analysed as above, the cooling system was found to have a satisfactory cooling capability for regions where ground water supply is available. Fer the other regions where ground water supply is restricted, more efficient cooling System should be developed.

• 대한수의학회지
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• 제38권2호
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• pp.394-400
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• 1998

Cryopreservation of embryos by vitrification is a simple method to preserve bovine embryos for subsequent embryo transfer, but embryonic viability after vitrification has been inconsistent and low compared with conventional slow freezing. The aim of the present study is to examine the effect of serum or serum albumin in a vitrification solution and epidermal growth factor(EGF) or fibroblast growth factor(FGF) on in vitro viability of bovine blastocysts frozen by vitrification. Bovine blastocysts were produced by in vitro maturation, fertilization of follicular oocytes and culture of embryos in a synthetic oviduct fluid medium(SOFM) containing BSA and 19 essential and nonessential amino acids. Blastocysts with excellent or good morphology were selected at 7 or 8 days after culture and utilized for vitrification. In experiment 1, blastocysts were vitrified in a solution containing semi-fetal calf serum(SFCS) or BSA(5 or 10mg/ml) and then their subsequent viabilities were examined by culturing thawed embryos in a SOFM containing BSA and 19 amino acids. Effect of EGF or FGF added to a SOFM containing polyvinyl alcohol(PVA) on the viability of vitrified-thawed blastocysts was investigated in experiment 2. BSA added at 5 or 10mg/ml to a vitrification solution showed significantly higher(p < 0.05) developmental rate to expanded and hatching blastocysts than SFCS, but there was no significant difference in the developmental rate to hatched blastocysts after thawing. Supplementation of a culture medium with EGF and/or FGF significantly increased(p < 0.05) embryo development to expanded blastocysts compared with control but showed no beneficial effect on the development to hatching or hatched blastocysts. Coculture of thawed embryos with granulosa cells in a TCM 199 containing 10% fetal calf serum(FCS) showed the highest developmental rate to expanded, hatching and hatched blastocysts among the groups tested. In conclusion, supplementation of a vitrification solution with BSA at 5mg/ml and culture of thawed blastocysts in a medium containing EGF and/or FGF can improve in vitro viability of bovine blastocysts frozen by vitrification.

• 한국결정성장학회지
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• 제2권2호
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• pp.11-19
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• 1992

$SrTiO_3$미분말은 초음파 분무 열분해법으로 chloride와 nitrate 수용액을 출발용액으로 사용하여 농도를 0.05M과 0.1M로 하였으며 각 농도에 따른 유속의 변화를 0.5cm/sec로 변화시켜 합성하였다. 분말의 형성 과정은 0.05M, 0.05cm/sec 조건에서 단계별 분말을 합성하여 주로 morphorlogy 측면에서 고찰하였다. 출발용액이 chloride 수용액인 경우 SrTiO$_3$미분말을 합성할 수 없었으며 nitrate 수용액인 경우 모든 조건에서 (110)면을 주 peak로 하는 cubic의 순수한 구형의 $SrTiO_3$미분말을 얻을 수 있었다. 평균입자의 크기는 유속이 증가함에 따라 $0.49{\mu}m$에서 $0.55{\mu}m$로 증가하였다. 출발액적의 크기는 $14.3{\mu}m$이었으며 단계별 입자의 형태는 1, 2단계에서 용매의 증발에 의해 매우 porous하였으며 불규칙하였고, 3, 4, 5단계를 지나는 동안 점차 둥근 형태로 형성되었다.

• 한국추진공학회지
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• 제9권3호
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• pp.120-126
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• 2005

액체산소(LOx)와 케로신(Kerosene)을 연료로 사용하는 액체로켓엔진 시험설비에서 지상연소시험을 수행할 경우에 발생하는 위험도를 감소시키는 방법을 연구하였다. 본 방법은 잠재적인 사고 발생확률을 낮추고 그에 따른 발생 가능한 손실을 낮추기 위해서 사고 발생 가능한 한계선에 대한 연구와 기술적 해결방법을 바탕으로 하고 있다. 시험설비에서 사고 상황을 야기 할 수 있는 위험한 상황에 관한 개략도와 추진제 유출 사고시 발전 양상 및 발전 프로세스에 대한 도표, 기술적인 해결방법, 위험성 감소 평가 방법을 제시함으로써 기존의 확률적인 통계 값을 바탕으로 하는 것과는 또 다른 방법으로써 위험도 감소를 위한 대안으로 사용하고자 한다.

• 한국세라믹학회지
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• 제29권12호
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• pp.963-969
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• 1992

This paper describes the feasibility for a direct production of zinc oxalate powders from zinc-loaded D2EHPA solutions combining the purification and the precipitation in one operation unit. This process has the potential as an alternative to conventional method for the synthesis of zinc oxide precursor particles from the hydrometal-lurgical processes. Zinc was extracted into D2EHPA in kerosene and then zinc-loaded D2EHPA solution was emulsified with oxalic acid-HCl solution to precipitate zinc oxalate powder, which was readily calcined to zinc oxide. The precipitation kinetics and yield were sensitive to experimental conditions. The morphology, size and size distribution of the zinc oxalate powders varied with zinc/oxalate ion riatio, temperature, and the presence of SPAN 60, which affected nucleation, growth, and the emulsion characteristics.