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진공성형을 이용한 삼엽식 고분자 심장판막의 제작과 혈류역학적 성능평가
김경현,황창모,정기석,안치범,김범수,이정주,남경원,선경,Kim, K.H.,Hwang, C.M.,Jeong, G.S.,Ahn, C.B.,Kim, B.S.,Lee, J.J.,Nam, K.W.,Sun, K. 대한의용생체공학회 2006 의공학회지 Vol.27 No.6
In the artificial heart application, productivity and hemodynamic properties of artificial heart valves are crucial in successiful application to long term in vivo trials. This paper is about manufacture and assessment of trileaflet polymer heart valves using vacuum forming process(VFP). The VFP has many advantages such as reduced fabrication time, reproducibility due to relatively easy and simple process for manufacturing. Prior to VFP of trileaflet polymer heart valves, polyurethane(Pellethane 2363 80AE, Dow Chemical) sheet was prepared by extrusion. The sheets were heated and formed to mold shape by vacuum pressure. The vacuum formed trileaflet polymer heart valves fabrication is composed of two step method, first, leaflet forming and second, conduit forming. This two-step forming process made the leaflet-conduit bonding stable with any organic solvents. Hydrodynamic properties and hemocompatibility of the vacuum formed trileaflet polymer heart valves was compared with sorin bicarbon bileaflet heart valve. The percent effective orifice area of vacuum formed trileaflet polymer heart valves was inferior to bileaflet heart valve, but the increase of plasma free hemoglobin level which reflect blood damage was superior in vacuum formed trileaflet polymer heart valves Vacuum formed trileaflet polymer heart valves has high productivity, and superior hemodynamic property than bileaflet heart valves. Low manufacturing cost and blood compatible trileaflet polymer heart valves shows the advantages of vacuum forming process, and these results give feasibility in in vivo animal trials in near future, and the clinical artificial heart development program.
홉ㆍ배기 시스템의 맥동류가 과급디젤기관의 체적효율에 미치는 영향
김경현(K. H. Kim),강희영(H. Y. Kang),고대권(D. K. Koh),안수길(S. K. Ahn),장재은(J. Y. Jang) 한국동력기계공학회 2006 한국동력기계공학회 학술대회 논문집 Vol.- No.-
This paper deals with an investigation of volumetric efficiency by fluctuations of the pressure, due to piston motion and valve event on intake and exhaust stroke, which occur in the intake and exhaust pipes of a three-cylinder four stroke turbo-charged engine. The volumetric efficiency affects significantly to the engine performance; torque characteristics, fuel economy and further to emission and noise level. As the expansion ratio became larger with the engine speed varies and torque increases, pressure pulsation in a exhaust gas pipe act as a factor of increasing intake air charging pressure totally. The phase and amplitude of pressure pulsation produced in the intake system affects on volumetric efficiency when it is matched and tuned effectively to engine. Thus, to verify and tracing of their pressure variation versus crank angle is a solution for the air-flow ratio assesment in the intake stroke. Some experimental results of pressure diagrams in the intake pipe and gas-flow of turbine in-out are presented, under various kinds of operating condition.
연료 분사시기가 전자제어 디젤엔진의 엔진 성능 및 배기 배출물에 미치는 영향
김경현(K. H. Kim),김주신(J. S. Kim),이한성(H. S. Lee),강희영(H. Y. Kang),고대권(D. K. Koh) 한국동력기계공학회 2009 한국동력기계공학회 학술대회 논문집 Vol.2009 No.11
This paper describes the engine performance and exhaust emissions of a direct injection diesel engine, operating electronically controlled diesel fuel injector with variable injection timing. Fuel injection was controlled to retard or advance initiation of the injection event by electronically controlled fuel injection unit injector. When fuel is injected into cylinders of a DI diesel engine it will go through ignition delay of processes before being exhausted to the outside. Injection timing of DI diesel engine has a significant effect upon performance and emission
김경현(K. H. Kim),강희영(H. Y. Kang),장지성(J. S. Jang),고대권(D. K. Koh),안수길(S. K. Ahn) 한국동력기계공학회 2008 한국동력기계공학회 학술대회 논문집 Vol.2008 No.11
Many engine designers are facing with legislative issues and engine performance. In the recent years, there are several technological advances to the spark ignition(SI) engine, such as, the variable valve timing(VVT) system. Empirical experiments have been undertaken to investigate the effect of intake valve closing(IVC) timing on the performance, e.x. the output, the torque and volumetric efficiency of the spark ignition engine. It was found that engine performance was significantly affected on the engine performance by intake valve closing timing. The valve timing optimization criteria were varied with the engine operating conditions.
헬름홀츠 공진기에 의한 유사 흡기시스템의 비정상유동 특성
김경현(K. H. Kim),강희영(H. Y. Kang),강경은(K. Y. Kang),고대권(D. K. Koh),안수길(S. K. Ahn) 한국동력기계공학회 2007 한국동력기계공학회 학술대회 논문집 Vol.- No.-
Unsteady flows in a semi-induction system was investigated to verify their characteristics. Inside of the induction system in a diesel engine, wave is generated and it affects significantly to breathing performance. The system consists of rotary valve, intake pipe and resonator. To make a air pulsation, a rotary valve was contrived and employed in this system. And also, A side-branched Helmholtz resonator is mounted in the intake pipe to enhance a breathing capacity. The phase and amplitude of the pulsating flow in an unsteady flow system were found to be the strong factor that could be significantly affects to charging capacity. Some of the results given from experiment are described.
김경현(K.H. KIM),강병희(B.H. Kang),전윤석(Y.S. Jun),목형수(H.S. Mok),최규하(G.H. Dhoe) 전력전자학회 2002 전력전자학술대회 논문집 Vol.- No.-
Recently, there are many researches in several places for a new resource, ahead. Also, Water of 70% m the earth it is interested and studied by around world. Long ago, in the side processing-use, it is making study the welding of Hydrogen-oxygen Gas, which is burned to acquired It( hydrogen + oxygen) by electric-disintegration into water, which has perfect-burning rather than exhaust carbon and It has excellent-sides in financials and efficiencies than existing-gas welding by sparking-characteristics of Hydrogen Oxygen gas. Therefore, with constant current source, It is intended to make a producing gas ratio through designing and making for the use of SCR rectifier of existing-formula and then m this paper it hopefully is coming up to characteristics of welding machine and producer of hydrogen oxygen gas with current-controlled type.