• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1992년도 제15회 학술강연회초록집
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• pp.82-96
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• 1992

동하중을 받는 엔진 베어링을 연구하기 위하여 1.5리터, 직렬 4 기통 가솔린 엔진 5개 메인 베어링 모두의 최소 유막 두께를 측정하고, 이론 계산을 수행하였다. 이론 계산은 무한 소폭으로 본 엔진 베어링에 대해 모빌리티 방법을 이용하였으며 유막두께 측정 방법으로는 TOTAL CAPACITANCE METHOD(TCM)을 사용하였다. TCM을 이용한 실험에서 실험의 정도를 높이기 위하여 새로운 베어링 틈새 설정 방법을 제시하였으며, 베어링 캐비테이션(Cavitation) 및 윤활유의 공기 혼입(Aeration)에 의한 시험오차를 해석하였다. 시험과 이론 계산의 결과를 비교한 결과, 정성적인 경향이 비교적 잘 일치하고 있음을 볼 수 있었다. 그러나 정정보로 가정된 이론 계산은 크랭크샤프트 진동 및 각 베어링이 받는 하중의 불균형으로 인한 영향을 예측하지 못함을 알 수 있었다. 엔진 운전중 베어링의 최대 전단율(Maximum Shear Rate)은 $10^7 S^{-1}$ 수준임을 확인하였다.

• 환경위생공학
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• 제11권3호
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• pp.63-68
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• 1996

This study was to discuss limiting factors influenced on the removal efficiencies of nitrogenous compounds investigated using the polypropyrene media which was to attach microorganism in order to apply the fixed-biofilm process. The main limiting factors are the hydraulic retention time (HRT), C/N ratio, $COD/NO_{3}-N$ ratio and temperature. The hydraulic retention time HRT were 6, 8, 10, 12 hrs and the C/N ratio range was 2.5-9.5. The $COD/NO_{3}-N$ ratio range was 3.2-21.9 and the temperature were 15, 20, 25, 30, $35^{\circ}C$, respectively. The results of this study are summerized as follows. 1. Hydraulic retention time (HRT) to obtain removal efficiencies of T-N higher than 85% had to be 10 hrs above. 2. The removal efficiencies of T-N decreased at C/N ratio from 6.2 to 4.8 in this anoxic-contact aeration system. 3. Denitrification rate decreased at $COD/NO$_{3}$-N$ ratio from 8.0 to 5.0 4. As temperature increased, removal efficiencies of T-N increased.

• Korean Membrane Journal
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• 제1권1호
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• pp.100-105
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• 1999

A novel system to thicken the concentrated colloidal solution from membrane water treat-ment processes was developed. A hollow-fiber microfilter(hydrophilic polyethylene nominal pore size 0.1 ${\mu}$m total surface area 0.42 m2) was installed in an acrylic housing that has an aeration port 5 cm below the membrane and a clarifier in the bottom. The concentrate was uniformly supplied from the top of the housing. Bacuum filtration caused downward flow of concentrate and as a result thickening interface. The addition of poly-aluminum chloride (PAC) resulted in rapid increase of trans-membrane pressure (TMP) and in no improvement of the filtered water turbidity and thickening process. Two types of con-centrate and concentrate turbidity had little effect on the increase of TMP and concentrate thickening. It was observed that for the same height of membrane housing membrane surface area to housing volume (A/V) ratio had significant effect on the increase of TMP. When the housing volume was increased ten times the increasing rate of TMP was three times faster as compared to the original housing. A hydraulic model successfully simulated the formation and sedimentation of thickening interface.

• 한국환경보건학회지
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• 제30권2호
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• pp.161-166
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• 2004

The impact of dissolved wastewater constituents on the treatment of synthetic bisphenol A (BPA) solutions was investigated under a variety of reaction conditions. The laccase enzyme from Trametes vesicolor was used for the BPA treatment. The constituents studied included various inorganic salts, organic compounds and heavy metal ions. BPA degradation was inhibited by sulfate, thiosulfate, sulfide, nitrite, and cyanide ions at 25 mg/$\ell$, 100mg/$\ell$, 25 mg/$\ell$ 150 mg/$\ell$, and 2.5 mg/$\ell$, respectively. However, the inhibitive effects of sulfide and sulfite on BPA degradation were diminished by additional aeration to oxidize them. Formaldehyde significantly reduced the rate of BPA degradation at 1.0% among organic compounds studied. Among heavy metal ions tested, Fe(II) substantially suppressed BPA removal at 1 mM. MgCl$_2$ and CaCl$_2$ exhibited great inhibition of BPA degradation at 25mM.

• KSBB Journal
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• 제6권4호
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• pp.379-383
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• 1991

Pervaporation can be successfully utilized to recover alcohol from fermentation broths and dilute process streams. Polydimethylsiloxane (thickness: $60\mu$m), such as hydrophobic membrane have been employed in this application to produce an enriched product. The fermented alcohol was continuously extracted, and simultaneously concentrated by pervaporation, from the membrane bioreactor, and the extracted alcohol concentration was 6 to 10 times higher than in the broth. This experimental conditions were 6-10 Torr vacuum line, pH=5, $32^{\circ}C$, 3.5 liters of working volume, 200rpm of agitator speed, and 0.14 wm aeration flow rate.

• Biotechnology and Bioprocess Engineering:BBE
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• 제10권2호
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• pp.103-108
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• 2005

For more accurately describing the durations of the light and the dark phases of micro-algal cells over the whole light-dark cycle, and probing into the relationship between the liquid circulation time or velocity, the aeration rate and cell density, a series of experiments was carried out in 10 cm light-path flat plate photobioreactors. The results indicated that the liquid flow in the flat plate photobioreactor could be described by liquid dynamic equations, and a high biomass output, higher content and productivity of arachidonic acid, $70.10\;gm^{-2}d^{-1},\;9.62\%$ and 510.3 mg/L, respectively, were obtained under the optimal culture conditions.

• 한국막학회:학술대회논문집
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• 한국막학회 1998년도 추계 총회 및 학술발표회
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• pp.150-152
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• 1998

Now the lack of water is serious problem all over the world because of the growth of population and expansion of industrial activities. So wastewater recycle and reuse is essential in many countries. One of the most popular wastewater treatment processes is conventional activated sludge system. In spite of significant degree of treatment rate the biological process has some operational difficulties and capital disadvantages. In conventional activated sludge process, sludge settling condition is getting worse in case of sludge bulking, it is common that overall process fails due to wash-out of biomass causing low concentration of MLSS in the aeration tank. Because of the absence of claifier the membrane bioreactor(MBR) process is less affected by such problems.

• Journal of Microbiology and Biotechnology
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• 제19권12호
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• pp.1603-1611
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• 2009

High-cell-density cultivation of yeast was investigated using the agricultural waste products corn steep liquor (CSL) and molasses. The Saccharomyces cerevisiae KV-25 cell mass was significantly dependent on the ratio between C and N sources. The concentrations of molasses and CSL in the culture medium were statistically optimized at 10.25% (v/v) and 16.87% (v/v), respectively, by response surface methodology (RSM). Batch culture in a 5-l stirred tank reactor using the optimized medium resulted in a cell mass production of 36.5 g/l. In the fed-batch culture, the feed phase was preceded by a batch phase using the optimized medium, and a very high dried-cell-mass yield of 187.63 g/l was successfully attained by feeding a mixture of 20% (v/v) molasses and 80% (v/v) CSL at a rate of 22 ml/h. In this system, the production of cell mass depended mainly on the agitation speed, the composition of the feed medium, and the glucose level in the medium, but only slightly on the aeration rate.

• 한국미생물·생명공학회지
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• 제23권5호
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• pp.624-631
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• 1995

The fermentation characteristics of Saccharomyces cerevisiae F38-1, a newly isolated thermotolerant yeast strain from a high temperature environment have been studied using a fermentation medium containing 20% glucose, 0.2% yeast extract, 0.2% polypeptone, 0.3% (NH$_{4}$)$_{2}$SO$_{4}$, 0.1% KH$_{2}$PO$_{4}$, and 0.2% MgSO$_{4}$ without shaking at 30$\circ$C to 43$\circ$C for 5 days. The fermentability was over 90% at 30$\circ$C, 88% at 37$\circ$C, 77% at 40$\circ$C and 30% at 43$\circ$C. A similar fermentation result was obtained at pH between 4 and 6 at 30$\circ$C and 40$\circ$C. Aeration stimulated the growth of the strain at the beginning of the fermentation, but it reduced alcohol production at the end of alcohol fermentation. Optimal glucose concentration was determined to be between 18 and 22% at 40$\circ$C as well as 30$\circ$C, but the growth was inhibited at the glucose concentration of over 30%. A fermentability of over 90% was observed at 40$\circ$C in 2 days when the medium was supplemented by 2% yeast extract. A higher inoculum size increased the initial fermentation rate, but not the fermentation. A fermentability of over 90% was achieved in 2 days at 40$\circ$C in a fermentor experiment using an optimized medium containing 20% glucose and 1% yeast extract.

• 한국환경농학회지
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• 제19권2호
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• pp.177-182
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• 2000

토양 미생물을 이용한 고농도 축산폐수의 과부하 처리를 위한 공정개발 연구결과 유기물 제거율은 99%이었다. 상온 혐기조에서 $0.7kg\;BOD/m^3/d$ 이하에서 처리수의 BOD 농도는 150mg/L 이하를 이었다. 상온 혐기조를 운전한 실험에서 후속 폭기조의 물질 대사계수(km)는 $0.73hr^{-1}$, 세포증식계수(Y)는 0.433 g/VSS/g BODrm/d 였으며 중온으로 운전한 경우 후속 폭기조에서 각각 $1.45hr^{-1}$과 0.776 g VSS/g BODrm/d 로 반응계수 값이 두 배에 가깝게 개선되었다.