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Reduction of Numerical Dispersion Error in 3-D ADI-MRTD Method With the Coarse Mesh
Jaejong Ryu,Wuseong Lee,Jugab Lee,Yeonkwan Moon,Hachul Kim,Hyunchul Choi IEEE 2009 IEEE microwave and wireless components letters Vol.19 No.8
<P>In order to reduce the numerical dispersion in three-dimensional alternating-direction implicit multiresolution time-domain scheme, a correction procedure is introduced. The numerical dispersion relation and the anisotropic correction parameters are considered. The reduction of the numerical dispersion is investigated for single frequency problem and wide-band simulation with the coarse mesh.</P>
Jaejong Ryu,Wuseong Lee,Hachul Kim,Hyunchul Choi 한국전자파학회JEES 2009 Journal of Electromagnetic Engineering and Science Vol.9 No.4
A three-dimensional locally one-dimensional multiresolution time-domain(LOD-MRTD) method is introduced and unconditional stability is proved analytically. The updating formulations have fewer terms on the right-hand side than those of an alternating direction implicit MRTD(ADI-MRTD). The validation of the method is presented using the resonance frequency problem of an empty cavity. The reduction of the numerical dispersion technique is also combined with the proposed method. The numerical examples show that the combined method can improve the accuracy significantly.
An Improved Split-Step Method in Scaling Function Based MRTD
Jaejong Ryu,Wuseong Lee,Hachul Kim,Hyunchul Choi IEEE 2010 IEEE microwave and wireless components letters Vol.20 No.4
<P>A split-step method with four sub-steps is applied to the multiresolution time-domain scheme and combined with the dispersion-error control parameters. From the discussed numerical dispersion, it is obvious that the phase velocity an- isotropic error and absolute error of the introduced method are much lower than alternating direction implicit and the original split-step MRTD method. The results show that this method can use three times the time step of the original SS-MRTD method.</P>
CNC 공작기계의 열변형 오차보정 (Ⅱ) : 알고리즘 및 시스템 인터페이스 중심 System Interface
이재종,최대봉,박현구,류길상 한국공작기계학회 2002 한국공작기계학회 추계학술대회논문집 Vol.2002 No.-
One of the major limitations of productivity and quality in metal cutting is the machining accuracy of machine tools. The machining accuracy is affected by geometric errors, thermally-induced errors, and the deterioration of the machine tools. Geometric and thermal errors of machine tools should be measured and compensated to manufacture high quality products. In metal cutting, the machining accuracy is more affected by thermal errors than by geometric errors. In this study, the compensation device and temperature-based algorithm have been implemented on the machining center in order to compensate thermal error of machine tools under the real-time. The thermal errors are predicted using the neural network and multi-regression modeling methods. In order to compensate thermal characteristics under several operating conditions, experiments performed with five gap sensors and manufactured compensation device on the horizontal machining center.
Functionalization of Microchannels with Micromixers by Patterning with a Focused Laser Beam
Lee, Sangwook,Ryu, Jihyeong,Jung, Daekyeong,Kim, Geehong,Choi, Kee-Bong,Lee, Jaejong,Lim, Hyungjun American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.11
<P>Microscale fluid mixing is required for many applications, from chemical processes to lab-on-a-chip systems. However, uniform microfluidic mixing is difficult at short mixing distances because typical micro flows with Reynolds numbers depend mostly on laminar diffusion. For a more effective mixing process, this paper focuses on the realization of microchannels with micromixers through the fabrication of nano-/micro-structures in microchannels with a focused laser beam. We developed a patterning system which can be used to fabricate geometric structures in microchannels in place of typical fabrication methods such as photolithography and etching. The system makes it possible to fabricate two-or three-dimensional geometries without masks due to its programmable software. The patterning process was added to a conventional microchannel fabrication process. We successfully fabricated two types of micromixers with the focused laser beam in 'Y'-shaped microchannels with a width of a few hundred micrometers. Finally, the mixing effect of functionalized microchannels was validated and the mixing distance was found to be shorter compared to that with microchannel without mixers.</P>
유연기판을 위한 UV/Thermal 하이브리드방식 나노임프린트 시스템
임형준(HyungJun Lim),이재종(JaeJong Lee),최기봉(Kee-Bong Choi),김기홍(GeeHong Kim),안현진(HyunJin Ahn),류지형(JiHyeong Ryu) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4
An UV/thermal hybrid nanoimprint lithography system was designed and implemented for the pattern transfer to flexible substrates. This system can utilize a plate stamp, roll stamp, and film stamp. For all cases of using those stamps, this system is also switchable an UV or thermal nanoimprint lithography mode. This paper shows how to design the heating and UV curing plates and proposes how to change them easily. Because the pressure condition and the speed of the press roller varies by the characteristics of the stamp and substrate, all the parameters related to the nanoimprint lithography have to adjustable. Some transferred patterns are shown in this paper to verify the performance of the hybrid nanoimprint lithography system. The flexible substrates with nano-scale patterns on them will be key components for next generation technologies such as flexible displays, bendable semi-conductors, and solar cells