• 대한기계학회논문집B
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• 제29권12호
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• pp.1360-1368
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• 2005

This study investigates the characteristics of spray, such as evaporation rate and spray trajectory, for a 4-hole injector which is applied to a 4-valve motorcycle gasoline engine. Three dimensional, unsteady, compressible flow and spray within the intake-port and cylinder have been simulated using the VECTIS code. Spray characteristics were investigated at 6000 rpm engine speed. Furthermore, we visualized fuel behavior in the intake-port using a CCD camera synchronized with a stroboscope in order to compare with the analytical results. Boundary and intial conditions were employed by complete 1-D simulation of the engine using the WAVE code. Fuel was injected into the intake-port at two time intervals relative to the position of the intake valves so that the spray arrived when the valves were closed and fully open. The results showed that the trajectory of the spray was directed towards the lower wall of the port with injection against the closed valves. With open valve injection, a large portion of the fuel was lifted by the co-flowing air towards the upper half of the port and this was confirmed by simulation and visualization.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.899-905
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• 2000

The characteristics of air flow and engine performance with swirl ratio variance of intake port In a turbocharged DI diesel engine was studied in this paper. The intake port flow is important factor which have influence on the engine performance and exhaust emission because the properties in the injected fuel depend on the combustion characteristics. The swirl ratio for ports was modified by hand-working and measured by impulse swirl meter. For the effects on performance and emission, the brake torque and brake specific fuel consumption were measured by engine dynamometer and NOx, smoke were measured by gas analyzer and smoke meter. As a result of steady flow test, when the valve eccentricity ratio are closed to cylinder wall, the flow coefficient and swirl intensity are increased. And as the swirl ratio is increased, the mean flow coefficient is decreasing, whereas the gulf factor is increasing. Also, through engine test its can be expected to meet performance and emission by optimizing the main parameters; the swirl ratio of intake port, injection timing and compression ratio.

• 한국자동차공학회논문집
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• 제10권2호
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• pp.23-30
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• 2002

This present study experimentally investigates the behavior of liquid and vapor phase of fuel mixtures with changing the in-cylinder air motion in an optically accessible engine. The conventional MPI/DOHC engine was modified to gasoline direct injection engine with swirl motion. The images of liquid and vapor phases were captured in the motoring operation condition using exciplex fluorescence method. Two dimensional spray fluorescence images of liquid and vapor phases were acquired to analyze spray behaviors and fuel distribution inside of cylinder respectively, In early injection timings $(BTDC\;270^{\circ},\;180^{\circ})$, tumble flow transported most of vapor phase to the lower region and the both sides of cylinder, so vapor phase didn't become uniform distribution up to the half of the compression stroke. In the case of swirl flow, the fuel mixture was confined near the swirl origin in upper region of cylinder. In late injection timings $(BTDC\;90^{\circ})$, tumble flow transported vapor phase to the intake valve and swirl flow to the exhaust valve.

• 한국자동차공학회논문집
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• 제23권1호
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• pp.97-104
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• 2015

This study is a part of the high pressure injection system development on the Turbo GDI engine in order to reduce smoke emission in case of using the low volatile(high DI) fuel which is used as normal gasoline fuel in the US market. Firstly, theoretical approach was done regarding gasoline fuel property, performance, definition of particle matters and its creation as well as problems of the high DI fuel. In this experimental study, 2L Turbo GDI engine was selected and optimized system parameter was inspected by changing fuel, fuel injection mode (single/multiple), fuel pressure, distance between injector tip and combustion chamber, start of injection, intake valve timing in engine dyno at all engine speed range with full load. In case of normal gasoline fuel, opacity was contained within 2% in all conditions. On the other hands, in case of low volatile fuel (high DI fuel), it was confirmed that the opacity was rapidly increased above 5,000 rpm at 14.5 ~ 20 MPa of fuel pressure and there were almost no differences on the opacity(smoke) between 17 MPa and 20 MPa fuel pressure. According to the SOI retard, smoke decrease tendency was observed but intake valve close timing change has almost no impact on the smoke level in this area. Consequently, smoke decrease was observed and 16% at 6000rpm respectively with injector washer ring installed. By removing injector washer to make injector tip closer to the combustion chamber, smoke decrease was observed by 46% at 5,500 rpm, 42% at 6,000 rpm. It is assumed that the fuel injection interaction with cylinder head, piston head, intake and exhaust valve is reduced so that impingement is reduced in local area.

• Journal of Chest Surgery
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• 제37권6호
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• pp.492-498
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• 2004

목적: 저자들은 본 연구에서 제I형 심실중격결손 환자에서 대동맥판막 병변 발생의 위험인자와 수술후 대동맥판막병변의 진행 양상과 수술 결과를 분석하여 제I형 심실중격결손의 수술시기와 치료전략을 확립하고자 하였다. 대상 및 방법 1991년 1월부터 2000년 12월까지 제I형 심실중격결손 또는 이에 동반된 대동맥판막병변에 대한 수술을 시행한 310예의 환자군을 대상으로 하였다. 환자의 평균연령은 73.7$\pm$114.7 (1∼737)개월이었으며 평균체중은 20.5$\pm$18.8 (3∼95) kg이었다. 진단 당시 대동맥 병변이 없는 경우가 186예(60%)였고 경도의 대동맥판폐쇄부전이 동반된 경우가 83예(27%), 중등도의 대동맥판폐쇄부전이 동반된 경우가 25예(8%), 중증 대동맥판폐쇄부전이 동반된 경우가 16예(5%)였다. 295예의 환자는 일차수술에서 동맥하심실중격결손만을 폐쇄하거나 (279예) 동시에 대동맥판막성 형술을 시행하거나 (5예), 대동맥판막치환술을 시행하였다(11예). 15예의 환자는 일차로 심실중격결손에 대해 수술을 받았던 환자 중 이차로 대동맥판막성형술을 시행하거나(4예), 대동맥판막치환술을 시행하였다(11예). 대동맥판폐쇄부전의 발생에 영향을 주는 위험인자를 분석하기 위하여 수술 당시 환자의 나이, 대동맥판막탈출증의 동반 여부, Qp/Qs, 수축기폐동맥압, 심실중격결손의 크기, 수축기 폐동맥압/체동맥압비 등을 분석대상 위험인자로 포함시켰다. 수술 당시 나이가 대동맥판폐쇄부전 발생에 미치는 영향을 보기 위해 환자군을 0∼1세(Group A: 102예), 1∼6 세(Group B: 136예), 6∼20세(Group C: 31예)로 나누었다. 대동맥판막의 수술방법에 따른 만기 수술 성적의 비교를 위해 대동맥판막성형술을 시행받은 9예와 대동맥판막치환술을 시행받은 22예의 술후 대동맥판막 기능을 비교하였다. 결과: 제I형 심실중격결손 환자에서 수술 당시 고연령, 대동맥판막탈출증 동반, 높은 Qp/Qs, 수축 기고폐동맥압 등이 대동맥판폐쇄부전 발생의 위험인자로 밝혀졌다(p<0.05, Table 2). 특히 수술 당시 연령이 높을수록 술 전 대동맥판폐쇄부전의 빈도가 높았으며 술 후 대동맥판폐쇄부전이 새로 발생하거나 진행하는 빈도가 높았다(p<0.05, Table 1, Fig. 1). 수술 당시 연령이 높은 환자에 대하여 판막대치술이 아닌 판막성형술을 한 경우 잔존 대동맥판폐쇄부전이 남는 경우가 의미있게 높았다 (p<0.05, Fig. 2). 결론: 결론적으로 대동맥판막의 병변 진행이나 발생을 억제하기 위하여 제I형 심실중격결손증에 대해서는 조기 수술이 권장되며 조기수술이 안 되어 병변의 진행이 심해지면 대동맥판막성형술의 완벽한 결과를 기대하기 어려운 경우가 적지 않으므로 병변이 심한 경우 대동맥판막대치술도 수술방법의 선택목록에 포함시켜야 한다.

• International journal of advanced smart convergence
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• 제4권1호
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• pp.54-63
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• 2015

Increasing air pollution levels and the global oil crisis has become a major hindrance in the growth of our automobile sector. Traditional Internal Combustion engines running on non-renewable fuels are proving to be the major culprit for the harmful effects on environment. With few modifications and also with assistance of few additional components current small SI engines can be modified into a pneumatic engine (commonly known as Compressed Air Engines) without much technical complications where the working fluid is compressed air. The working principle is very basic as adiabatic expansion of the compressed air takes place inside the cylinder pushing the piston downwards creating enough MEP to run the crank shaft at decent RPM. With the assistance of new research and development on pneumatic engines can explore the potential of pneumatic engines as a viable option over IC engines. The paper deals with analysis on RPM variation with corresponding compressed air injection at different crank angles from TDC keeping constant injection time period. Similarly RPM variation can also be observed at different injection pressures with similar injection angle variation. A setup employing a combination of magnetic switch (reed switch), magnets and solenoid valve is used in order to injection timing control. A conclusive data is obtained after detailed analysis of RPM variation that can be employed in newly modified pneumatic engines in order to enhance the running performance. With a number of benefits offered by pneumatic engine over IC engines such as no emissions, better efficiency, low running cost, light weight accompanied by optimized injection conditions can cause a significant development in pneumatic engines without any major alteration.

• Journal of Yeungnam Medical Science
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• 제37권4호
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• pp.345-348
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• 2020

Papillary fibroelastomas are the second most common primary cardiac tumor in adults. Over 80% of fibroelastomas occur on the cardiac valves, usually on the left side of the heart, while the remaining lesions are typically scattered throughout the atria and ventricles. Although the optimal timing for surgery is controversial and depends on tumor size and location, prompt surgical resection is warranted in patients at high risk of embolism. A tumor on the cardiac valve can be removed using the slicing excision technique without leaflet injury. Here we present two cases of papillary fibroelastomas occurring on the ventricular surface of the aortic valve and in the right ventricle.

• Tribology and Lubricants
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• 제14권2호
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• pp.63-74
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• 1998

The damage of cam/tappet surface is one of the major reasons for energy loss in an I.C. engine. High friction causes the accelerated wear of the cam/tappet surfaces which in turn changes the valve opening/closing timing. During the accelerated test evidence of both rolling fatigue and sliding abrasive wear could be found. Based on the results of the accelerated test, a scheme was devised to decrease tappet wear. Wear reduction of the tappet was achieved by using undulated surface topography in the tappet center region. The wear reduction is achieved by trapping of the wear particles in the undulations as well as by increasing the supply of lubricant to the sliding interface.

• 한국자동차공학회논문집
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• 제9권1호
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• pp.63-74
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• 2001

In this study, a cycle simulation program of a Unit-Injection(UI) system was developed to estimate the injection performance of newly designed injection system. A fundamental theory of the simulation program is based on the conservation law of mass. Loss of fuel mass in the system due to leakage, compressibility effect of the liquid fuel and friction loss in the control volume was considered in the algorithm f the program. For the evaluation of the simulation program developed, the experimental result which was offered by the Technical Research Center of Doowon Precision Industry Co. was incorporated. Two main parameters; the maximum pressure in the plunger chamber and total fuel mass(kg) injected into the engine cylinder per cycle, were measured and compared with the simulation results. It was found that the maximum error rate of the simulation result to the experimental output was less than 3% in the rated rotational speed (rpm) range of the plunger cam.

• 한국자동차공학회논문집
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• 제17권5호
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• pp.107-114
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• 2009

A Common-Rail Direct Injection (CRDI) system for high speed diesel engines was developed to meet reductions of noise and vibration, emission regulations. High pressure in the common rail with electric control allows the fuel quantity and injection timing to be optimized and controlled throughout a wide range of engine velocity and load conditions. In this study, CRDI system analysis model which includes fuel and mechanical systems was developed using commercial software, AMESim in order to predict characteristics for various fuel injection components. The parameter sensitivity analysis such as throttle size, injection rate, plunger displacement, supply pressure of fuel injection for system design are carried out.