• 한국정밀공학회지
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• 제28권7호
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• pp.827-833
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• 2011

Precision forging of gears has a lot of advantages when compared to conventional gear shaping, because it allows the manufacture of gear parts without flash and consequently without the need for subsequent machining operations. In this study, the cold forging process is determined to manufacture the cold forged product for the precision clutch gear used of a commercial automobile, To do this, shape ratio of initial shape having influence the forgeability of forged product is analyzed. The optimal initial shape of clutch gear is designed using the results of DEFORM-3D and the artificial neural network (ANN). The initial shape through the detail analysis results, such as metal flow, distributions of strain can be obtained.

• 한국추진공학회지
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• 제19권2호
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• pp.38-45
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• 2015

본 연구에서는 고고도의 저압환경 구현을 목적으로 사용되는 이젝터의 설계기법을 정립하고 상온가스를 이용한 실험을 통하여 성능변수와 형상변수에 따른 이젝터 작동 특성을 관찰하였다. 유량비, 압축비, 팽창비를 성능변수로 선정하고, 간극비를 형상변수로 선정하여 실험을 수행하였다. 실험결과 이젝터의 성능을 예측할 수 있는 성능변수들의 관계를 파악하였으며, 간극비 보다는 성능변수가 이젝터의 성능에 큰 영항을 미치는 것을 확인하였다.

• 설비공학논문집
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• 제20권11호
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• pp.767-774
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• 2008

This paper presented the heat transfer and pressure drop characteristics for micro plate heat exchanger with straight channel. The metal sheets for straight channel are manufactured by chemical etching and fabricated micro plate heat exchangers by using the vacuum brazing of bonding technology. The performance experiments are performed within the Reynolds numbers range of 15$\sim$250 under the same flow rate conditions for hot and cold sides. The inlet temperature of hot and cold water are conducted in the range of $30^{\circ}C{\sim}50^{\circ}C$ and $15^{\circ}C{\sim}25^{\circ}C$, respectively. Heat transfer rate and pressure drop are evaluated by the Reynolds numbers and mass flow rates as the inlet temperature variations of the hot and cold sides. Correlations of Nusselt number and friction factor are suggested for micro plate heat exchanger with straight channel using the results of performance experiment.

• 한국해양바이오학회지
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• 제6권2호
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• pp.47-52
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• 2014

Oxidation stability and cold fuid property are considered as the most important factors for determining biodiesel quality. Among the fatty acids, monounsaturated fatty acid satisfy both oxidation stability and cold flow property of biodiesel quality standards. Microalgae with high monounsaturated fatty acid contents is have some benefit for producing to produce biodiesels with satisfying quality standards. In this study, monounsaturated fatty acid contents of a isolated microalga from Youngheung island was analyzed. Phaeodactylum tricornutum was isolated by streaking, and growth rate and fatty acid composition of the algae were investigated. Total FAME contents were consisted of 26% of saturated fatty acids, 43% of monounsaturated fatty acids, and 18% of polyunsaturated fatty acids. The contents of monounsaturated fatty acid were especially high in the Phaeodactylum species. This result implies that the FAMEs from P. tricornutum may contribute to improve the oxidation stability and cold flow property of biodiesel.

• 한국산학기술학회논문지
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• 제15권2호
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• pp.653-659
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• 2014

자동차용 LPI 연료필터 하우징의 냉간단조 공정에 대한 성형해석을 수행하였다. 변형과 하중의 분배를 고려하여 금형과 시제품을 제작하였다. 또한 기존 모델과 신규 모델의 유동 특성을 분석하기 위하여, 유동해석을 수행하였다. 유동해석 결과, 두 모델은 동등한 압력강하량을 나타내었다. 기존 제품 대비, 상부 하우징은 16 g, 하부 하우징은 30.5 g이 감소하여, 총 46.5 g의 중량이 감소하였다. 안정성을 검증하기 위해서 기밀시험 및 내압시험을 수행하였으며, 시험 기준을 만족하였다.

• 해양환경안전학회지
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• 제20권1호
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• pp.96-103
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• 2014

극저온 액체 상태의 LNG는 주거용과 산업용으로 공급되기 전에 가스 상태로 변환된다. 이러한 재가스화 과정 중에 LNG는 $83.7{\times}10^4$ kJ/kg 정도의 많은 냉열에너지를 제공한다. 이 냉열에너지를 일부 선진국들에서는 질소, 수소, 헬륨과 같은 극저온 유체들의 액화, 제빙 및 냉방시스템에 이용하고 있다. 따라서 우리나라에서도 인천, 평택 및 통영 LNG 인수기지 주변에 LNG의 냉열에너지를 이용한 냉열에너지 회수시스템을 설립할 필요가 있다. 여기서는 저열유속상태에서 상변화를 동반하는 LNG의 유동거동 특성을 파악하기 위해 LNG의 85 %를 차지하는 메탄을 작동유체로 사용하였다. 또한 본 논문은 극저온 열교환기 내부를 흐르는 메탄과 질소, 프로판, R11 및 R134a의 유동경계에 영향을 주는 관 직경, 관의 경사각도 및 포화압력의 효과를 보여준다. 또한 여기서 얻어진 이론적 연구결과와 기존의 실험 데이터와도 비교 되었다. 그리고 메탄의 유동경계에 주는 파이프의 경사각도의 영향은 매우 큼을 알 수 있었다.

• 소성∙가공
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• 제10권2호
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• pp.151-159
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• 2001

Flow defect of a piston-pin for automobile parts is investigated in this study. In combined cold extrusion of piston-pin, lapping defect, which is a kind of flow defect, appears by the dead metal zone. This appearance evidently happens in products with a thin thickness to be pierced for the dimensional accuracy and the decrease of material loss. The flow defect that occurs in piston-pin has bad effects on the strength and the fatigue life of piston-pin. Therefore, it is important to predict and prevent defects in the early stage of process design. The best method that can prevent flow defect is removing or reducing dead metal zone through material flow control. The finite element simulations are applied to analyze the flow defect. This study proposes processes for preventing flow defect by removing dead metal zone. Then the results are compared with the experimental ones for verification. These FE simulation results are in good agreement with the experimental ones.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.63-65
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• 2008

CFD cold-flow analysis results of the air-blast swirl nozzle for the small aircraft engine combustor are shown. Two major recirculation zones are observed near the nozzle. The centerline recirculation zone velocity profile of CFD is compared with the experimental results.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.249-252
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• 2006

We conducted the experiment to analyze characteristics of micro-nozzle using different cold gas under two different nozzle expansion ratios in low vacuum condition. We measured thrust and chamber pressure and mass flow rate under low vacuum condition, and then compared them with those in ambient pressure.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.617-621
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• 2004

Miniaturization of subsystems including propulsion systems is recent trends in spacecraft technology. Small space vehicle propulsion is not only a technological challenge of a scaling system down, but also a combination of fundamental flow/combustion constraints. In this paper, physical constraints of micronozzle for cold gas micro-thruster are reviewed and discussed. Method to measure small thrust are also described.