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전기장 변화에 따른 3차원 비정상 상태 열전달 연계 해석에 관한 연구
곽이구(L. K. Kwac),김홍건(H. G. Kim) 한국생산제조학회 2008 한국생산제조학회지 Vol.17 No.1
A modeling technique for the 2-way coupling of heat transfer and conduction currents has been performed to inspire a combined analytical simulation. The 3-D finite element method is used to solve steady conduction currents and heat generation in an aluminum film deposited on a silicon substrate. The model investigates the temperature in the device after the current is applied. The conservation equation of energy, the Maxwell equations for conduction currents, the unsteady state heat transfer equation and the Fourier’s law for heat transfer are implemented as a bidirectionally coupled problem. It is found that the strongly coupled temperature and time dependent heat equations give a reasonable results and an explicit solving technique.
연료전지 전극(Cathode)의 성능해석 및 설계에 관한 연구
김홍건(H. G. Kim),강성수(S. S. Kang),곽이구(L. K. Kwac),송하영(H. Y. Song),강영우(Y. W. Kang) 한국생산제조학회 2007 한국생산제조학회지 Vol.16 No.1
The cathode design is one of the most important parts in order to enhance the performance of fuel cells. A 3-D model of the porous oxygen reducing cathode with perforated current collectors is analysed for the enhanced design in fuel cells. Simulation is performed using equations of electric potential balance, momentum balance, and mass balance. The gas concentrations are quite large and are significantly affected by the reactions that take place. The weight fraction of oxygen, velocity field for the gas phase, and local overvoltage are illustrated in the porous reactive cathode layer. The current density is also analysed and the result shows the distribution and variation are stated in a wide range. It is found that the rate of reaction and the current production is higher beneath the orifice, and decreases as the distance to the gas inlet increases. The significance of the results is discussed in the viewpoint of the mass transportation phenomena, which is inferred that the mass transport of reactants dictates the efficiency of the electrode in this design and at these conditions.
UPCU의 초정밀위치결정에 따른 가공정밀도 향상에 관한 연구
김재열(J. Y. Kim),곽이구(L. K. Kwac),곽남수(N. S. Kwak),고명석(G. M. Seok) 한국생산제조학회 2006 한국생산제조시스템학회 학술발표대회 논문집 Vol.2006 No.5
The ultra-precision products which recently experienced high in demands had included the large areas of most updated technologies, for example, the semiconductor, the computer, the aerospace, the media information, the precision machining. For early 21st century, it was expected that the ultra-precision technologies would be distributed more throughout the market and required securing more nation-wise advancements. Furthermore, there seemed to be increasing in demand of the single crystal diamond tool which was capable of the ultra-precision machining for parts requiring a high degree of complicated details which were more than just simple wrapping and policing. Moreover, the highest degree of precision is currently at 50 ㎚ for some precision parts but not in all. The machining system and technology should be at very high performed level in order to accomplish this degree of the ultra-precision.
UPCU의 초정밀위치결정에 따른 가공정밀도 향상에 관한 연구
김재열(J. Y. Kim),곽이구(L. K. Kwac),곽남수(N. S. Kwak),고명석(G. M. Seok) 한국생산제조학회 2006 한국공작기계학회 춘계학술대회논문집 Vol.2006 No.-
The ultra-precision products which recently experienced high in demands had included the large areas of most updated technologies, for example, the semiconductor, the computer, the aerospace, the media information, the precision machining. For early 21st century, it was expected that the ultra-precision technologies would be distributed more throughout the market and required securing more nation-wise advancements. Furthermore, there seemed to be increasing in demand of the single crystal diamond tool which was capable of the ultra-precision machining for parts requiring a high degree of complicated details which were more than just simple wrapping and policing. Moreover, the highest degree of precision is currently at 50 ㎚ for some precision parts but not in all. The machining system and technology should be at very high performed level in order to accomplish this degree of the ultra-precision.