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혈액펌프내 혈액 변성 예측에 대한 Lagrangian 및 Eulerian 기법의 평가
홍성민(S. Hong),손창근(C. Son),강성원(S. Kang),허남건(N. Hur),김원정(W. Kim),강신형(S.H. Kang) 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.3
A blood pump is an important part of a cardiac assist device. Since the shear rate in blood is known to be a primary factor on hemolysis generation, it has been very important to evaluate hemolysis inside blood pumps for understanding performance and reliability of cardiac assist devices. In this study, hemolysis generation inside blood pumps is analyzed using CFD with power-law based models for the blood damage index(BDI), in order to overcome difficulties in measuring hemolysis by experiment. The BDI values in blood pumps can be evaluated using Lagrangian or Eulerian approaches. In this study, several Lagrangian and Eulerian approaches are compared to estimate the efficiency of the numerical methods in a practice sense. It is found that the Eulerian approaches are advantageous in terms of the efficiency and robustness. Two different Eulerian approaches are used to evaluate the BDI values of a few commercial blood pumps. For the conditions of extracorporeal membrane oxygenator(ECMO) and ventricular assist device(VAD), local generation of hemolysis is analyzed using divided regions of blood pumps, in order to investigate the effects of the pump geometry.
홍성민(S. M. Hong),이동주(D. J. Lee),제태진(T. J. Jae),최두선(D. S. Choi),이응숙(E. S. Lee) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월
Micro spherical lens mold processing method based on mechanical one completes a spherical shape by setting a diamond tool of hundreds μm radius on spins with high speed and then using Z-axis vertical feeding motion like the fabrication of micro drilling. In this method, we can see unprocessed parts shaped like cylinder and cone and check increasing chatter marks and burrs by setting errors of the central axis of rotation on the edge of the tool. That is why this method doesn’ t suit for the optical lens mold. In this paper presents unprocessed parts are disappeared and chatter marks and burrs are decreased from centre of the lens after using Run-out measuring and setting system on run-out occurred from setting tool. Also the fabrication characteristics of 6:4 Brass, A1601, PMMA are compared and analyzed, establishing the optimum machining condition on each material.
Wavelet 변환을 이용한 음성비화기의 설계 및 구현
홍성민(S.M.Hong),김성환(S.W.Kim),오상엽(S.Y.Oh),유경렬(K.R.Yoo),윤현수(H.Yoon),이홍규(H.K.Lee) 한국정보과학회 1995 한국정보과학회 학술발표논문집 Vol.22 No.1
군용과 같은 특수목적의 음성통신에 주로 사용되는 음성비화기법은 음성을 어떤 형태로든 섞어서 도청자가 알아듣지 못하도록 하는 기술이다. 최근, 디지탈 음성 암호화 기술이 소개되었지만, 디지탈화에 따른 음성암호화기의 속도 및 저속 음성코딩/채널코딩에 따른 음질의 저하 등을 고려해 볼 때, 실제적인 음성통신의 보안을 위해서는 아날로그 음성비화기법이 유용하다. 본 논문에서는 종래의 FFT를 기반으로 하는 음성비화기가 가지는 잔류가청성 등의 문제를, wavelet 변환을 이용하여 설계함으로써 해결할 수 있음을 보인다. 또한, 본 논문에서 설계된 음성비화기에 대해, 실제 음성에 대한 실험을 통하여, 음성의 비화 정도와 복원된 음성의 음질을 평가하였다.
제태진(T. J. Je),최두선(D. S. Choi),이응숙(E. S. Lee),황경현(K. H. Hwang),홍성민(S. M. Hong),이종찬(J. C. Lee) 한국생산제조학회 2005 한국공작기계학회 추계학술대회논문집 Vol.2005 No.-
With mechanical machining method, manufacturing of the micro pattern structure like micro lens array has been next to impossible. So till now, lithography or etching method has been used widely in manufacturing micro lens array mold. Mechanical micro lens array mold technology still on the step of technological development. when it comes to commercializing, accompanies some problems in tools and machining method. The diamond tool for machining micro lens is a rotational tool having designated spherical cutting edge. Therefore, the machining is influenced by tool design and manufacturing, setting accuracy of cutting edge on the axis of rotation, and run-out accuracy. etc. This paper presents these: analysis of machined surface's shape at the position of cutting edge and run-out error at tool setting; considerations in tool designing and manufacturing; methods of reduction at run-out error, when machining micro lens with the end-milling method using a single-edge semi-spherical tool.