• 대한환경공학회지
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• 제34권10호
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• pp.671-677
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• 2012

본 연구는 에멀젼 연료의 특성과 배출가스에 대하여 연구하였다. 엔진 배출가스 측정은 엔진 dinamometer로 실시하였다. 실험분석 결과 emulsion 연료의 참발열량과 총발열량은 이론적 계산과 실제측정결과 오차범위인 ${\pm}0.5%$로 산정된다. 점도와 밀도는 물의 첨가량이 증가할수록 증가하였다. 또한 emulsion 연료는 보관온도가 높아질수록 상분리가 빠르게 진행된다. $20^{\circ}C$의 경우가 가장 안정된 상태를 오래 유지하며, 그 다음은 $50^{\circ}C$가, 가장 불안정한 상태를 보이는 것은 $80^{\circ}C$인 것을 알 수 있었다. 연소실험 결과 emulsion 연료가 Bunker-A 보다 낮은 NOx, Smoke 수치를 보였으며, 총 NOx는 1,000 rpm 41%, 1,200 rpm 10%, 1,500 rpm 32% 2,500 rpm 28%, 총 smoke는 1,000 rpm 42%, 1,200 rpm 65%, 1,500 rpm 70%. 2,000 rpm 62%. 2,500 rpm 82%의 저감이 가능하였다.

• 한국유체기계학회 논문집
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• 제12권6호
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• pp.41-46
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• 2009

This paper deals with the operating-speed (high-speed) balancing of a refinery gasoline HDS (hydrodesulfurization) process recycle-gas 8-stages compressor rotor. A low-speed balancing condition of the rotor was measured as maintaining the G2.5 level. But an inspection run of operating-speed balancing condition, using tilting-pad journal bearings of actual use, showed that while it could be continuously-operated safely at a rated speed of 10,500 rpm, the rotor would not be able to run over 11,000 rpm as the vibration increased very sharply, approaching 11,000 rpm. In order to cure that a series of operating-speed balancing, which first calculated balance correction-weights by applying the influence coefficient measured and calculated at 10,500 rpm and then implemented correction works, was carried-out. The final operating-speed balancing results showed that the vibrations at the bearing pedestals represented very good levels of 0.2 mm/s by decreasing to as much as the 1/10 of the original vibrations and particularly, even at a targeted maximum continuous operating speed, MCS, of 11,500 rpm the vibrations represented about 1 mm/s, which is the operating-speed balancing vibration specification of API. Therefore, the expansion of MCS was successfully accomplished through the operating-speed balancing.

• 대한치과보철학회지
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• 제30권2호
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• pp.167-189
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• 1992

Frictional heat produced by cutting tools during dental implantation procedure may destroy the surrounding bone tissue and regenerative capacity and interfere ossointegration by formation of undifferentiated connective tissue. To study the effect of frictional heat according to various rotational speeds on the regenerative capacity of surrounding bone tissue, 13 ITI HS implants (8 mm) were inserted at 4 mongrel dogs. Temperatures were measured using thermocouple located 6 mm below from the marginal crest and 0.5 mm from the periphery of trephine mill during implant bed preparation. After 4 and 9 months, animals were sacrificed and specimens were examined using x-rays and light microscope. Results were as follows: 1. With drill speeds of 300, 800, 2,000, 3,500 rpm and saline irrigation, temperatures of surrounding bone were decreased from $-2.9^{\circ}\;to\;-1.7^{\circ}C$. Temperature rises of $2.0^{\circ}\;and\;2.1^{\circ}C$ were recorded with a drill speed of 5,000 rpm and irrigation. 2. With drill speeds of 800, 3,500, 5,000 rpm and no irrigation, temperatures of surrounding bone rose from $+1.5^{\circ}\;to\;+6.8^{\circ}C$, but maximum temperature was $40^{\circ}C$ at 5,000 rpm. 3. On radiographic examination, bone resorptions were observed at the upper half of implant of 5,000 rpm without irrigation and one case of 5,000 rpm with irrigation. 4. Osseointegration was unsuccessful in cases of 3,500, 5,000 rpm without irrigation due to fibrous connective tissue formation to the outer surface and hollow, but it was successful in a case of 800 rpm without irrigation. 5. Osseointegration was successful in cases of 300, 800, 2,000 and 3,500 rpm with irrigation. But fibrous connective tissue formation was observed at the hollow of implant inserted with 5,000 rpm with irrigation.

• 상하수도학회지
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• 제13권3호
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• pp.107-115
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• 1999

The general objectives of this study are to develop a new biofilm reactor equipped with agitating mixer and to evaluated the treatment efficiency of the reactor. The experimental tests were conducted to estimate the oxygen transfer rate of agitating mixer system. Results are as follows. 1. The oxygen transfer coefficient, KLa, was $8.94hr{-1}$ and $7.50hr{-1}$ at 500rpm and 250rpm of agitating mixer speed, respectively. When the agitating mixer was used in the biofilm reactor, 22.5% and 18.8% of oxygen transfer rates were increased at 500rpm and 250rpm, respectively. 2. The removal rate of BOD and CODcr was decreased by 5.0% when the agitating mixer speed was varied from low (250rpm) to high level (500rpm). 3. The concentration of attached biomass had a difference of 5.0% to 7.3%, whereas that of suspended biomass had a difference of about 15.0%, depending upon variation of the agitating mixer speed.

• Restorative Dentistry and Endodontics
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• 제10권1호
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• pp.161-168
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• 1984

The purpose of this study was to examine the effect of heat generated by rotating bur on the dental hard tissue in vitro. Freshly extracted molar teeth with normal appearance from early 20's male were collected and experimental teeth were divided into 4 groups and the teeth in each group were prepared class I cavity with different clinical procedures as follows. The four methods were. I. 20,000rpm without coolant II. 20,000rpm with coolant III. 500,000rpm without coolant IV. 500,000rpm with coolant Five teeth were reserved intact as a control group. These teeth were longitudinally split into two parts by means of chisel after class I cavity preparation. In a control group 5 parts were boiled in water for 20 minutes and the other 5 specimens were not boiled. All specimens were immersed in 2% methylene blue dye solution and the image of dye penetration was examined and photographed under stereomicroscope. Followings were the results obtained through the study. 1. In control group, dye penetration of the unboiled specimens was increased than with the boiled group. 2. The specimens prepared cavity without coolant showed decreased dye penetration than with the coolant group. 3. 20,000rpm without coolant group showed the least dye penetration. 4. 500,000rpm with coolant group showed similar level of dye penetration to the unboiled specimens from the control group.

• Journal of Periodontal and Implant Science
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• 제39권sup2호
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• pp.253-259
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• 2009

Purpose: This study was aimed to evaluate the effect of implant drilling speed on the composition of particle size of collected bone debris. Methods: $Br{\aa}nemark$ $System^{(R)}$ drills were used to collect bone debris from 10 drilling holes (1 unit) at 1,500 rpm (Group A) and 800 rpm (Group B) in bovine mandible. After separating particles by size into > 500 ${\mu}m$, between 250 ${\mu}m$ and 500 ${\mu}m$, and < 250 ${\mu}m$ fractions, particle wet volume, dry volume, and weight were measured and the proportion of 3 fractions of bone debris to total wet volume, dry volume and weight was calculated as wet volume % , dry volume % and weight %. Results: No significant differences were found between Group A and B in wet volume, dry volume, and weight. However, of >500 ${\mu}m$ fractions, Group B had significantly higher wet volume %(P = 0.0059) and dry volume %(P = 0.0272) than in Group A. Conclusions: The drilling speed influenced the composition of particle size in collected drilling bone debris. The drilling in 800 rpm produced the more percentage of large particles than in 1,500 rpm. However, the drilling speed didn't effect on total volume of and weight of bone debris.

• 유기물자원화
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• 제11권4호
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• pp.114-119
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• 2003

본 연구는 남은 음식물의 사료화를 목적으로 Lactobacillus acidophilus와 Saccharomyces cerevisiae를 이용하여 남은 음식물을 발효시켜 고품질의 생균사료를 생산하기 위하여 실시하였다. 액상으로 충분히 마쇄시킨 남은 음식물 시료에 공기주입량을 0v.v.m 0rpm, 0.25v.v.m 100rpm, 0.5v.v.m 200rpm과 1v.v.m 500rpm으로 다르게 조절하여 $30^{\circ}C$에서 발효시킨 결과 0.5v.v.m 200rpm의 조건에서 생균수가 $4.5{\times}10^9CFU/m{\ell}$로 가장 높은 것으로 나타났다. 또한 공기주입량을 조절함으로써 최종 발효물의 pH를 조절할 수 있었고 사료로서의 기호성에 알맞고 보존성도 좋은 4-5의 pH범위를 얻을 수 있었다.

• 한국수소및신에너지학회논문집
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• 제26권3호
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• pp.287-293
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• 2015

The current study has investigated the effects of biodiesel blended with gasoline on the spray characteristics in a Constant Volume Combustion Chamber (CVCC). With the concentration of 5, 10, 15 and 20% by volume, biodiesel was blended with commercial gasoline and performed on the macroscopic visualization test. Pure gasoline and biodiesel were also tested as the reference. The shadowgraph technique was conducted in the constant volume chamber. The spray images were recorded by a high speed video camera with frame speed 10,000 frame per second. Fuel injection was set at 800, 1000 and 1,350 bar with the simulated speed 1,500 and 2,000 rpm. The back pressure was controlled at 20 bar. The spray angle and penetration tip were measured and analyzed by using the image processing. At the high injection pressure, the spray penetration length with the simulated speed 1,500 rpm showed that B100 was lower than GB00-20 whereas the spray penetration length with the simulated speed 2,000 rpm exhibited that GB blends and B100 were insignificantly different. Due to biodiesel concentration, its effects on spray angles were observed throughout injection periods (T1, T2 and T3). At the simulated speed 1,500 rpm, the spray angle of GB blends and B100 presented the same pattern following injection timing. In addition, when the simulated speed increased to 2,000 rpm the different spray angle of all blends disappeared at main injection (T3).

• KSBB Journal
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• 제19권1호
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• pp.78-82
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• 2004

곰팡이인 Mortierella alpina DSA-12를 이용한 arachidonic acid의 생산을 위한 유기질소원의 선정과 배양 조건의 결정에 연구를 수행하였다. Corn steep powder (CSP)를 원료의 가격과 arachidonic acid의 생산을 기준으로 유기질소원으로 선정하였다. 탄소원으로 glucose와 질소원으로 CSP를 사용한 경우에 최적의 C/N ratio는 15-17 범위이다. Arachidonic acid의 생산을 위한 최적의 배양조건은 $25^{\circ}C$에서 500 rpm의 교반과 0.5 vvm의 통기이며, 이 때 50 g/L의 glucose와 18 g/L의 CSP로부터 21.8 g/L의 균사체량에 10.2 g/L의 총 지질을 얻을 수 있었으며, arachidonic acid의 농도는 3.70 g/L이었다. 500 L의 발효조에서 0.5 vvm과 200 rpm의 교반으로 실험을 수행한 결과 19.8 g/L의 균사체량과 9.1 g/L의 총 지질 및 3.67 g/L의 arachidonic acid를 얻었다. 이러한 결과는 bench-scale의 발효조에서도 질소원으로 CSP를 이용하여 arachidonic acid의 생산이 가능함을 보여주었다.

• Korean Chemical Engineering Research
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• 제47권5호
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• pp.651-654
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• 2009

본 연구는 팜유 바이오 디젤을 제조하기 위하여 초임계 메탄올을 이용한 무촉매 전이에스터화반응을 수행하였다. 메탄올에 대한 오일의 몰 비(30:1~60:1), 압력(8~25 MPa), 온도($320{\sim}350^{\circ}C$), 교반속도(0~1,000 rpm), 시간(0~20 min)과 같은 반응 인자들이 지방산메틸에스터의 함량에 미치는 영향을 알아보기 위하여 회분식 반응기를 이용하여 실험하였다. 팜유에 대한 메탄올의 몰 비가 높아질수록 지방산메틸에스터의 함량이 높아졌지만, 45:1 이상에서는 미치는 영향이 적었으며, 각각의 몰 비에서 20 MPa 이상의 압력에서는 함량의 변화가 거의 없었다. 반응온도가 증가함에 따라 지방산메틸에스터의 함량이 증가하였지만, $350^{\circ}C$ 이상 반응시간 5 min 이후부터 감소하였고, 500 rpm 이상의 교반속도에서는 교반이 미치는 영향이 거의 없음을 확인할 수 있었다. 몰 비 45:1, 온도 $335^{\circ}C$, 압력 20MPa, 시간 10분, 교반속도 500 rpm인 반응조건에서 최대 지방산메틸에스터 함량인 95%를 얻을 수 있었다.