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펨토초 및 나노초 레이저를 이용한 박막태양전지의 레이저 플라즈마 분광 분석
이석희,최장희,정성호,Lee, S.H.,Choi, J.H.,Gonzalez, J.J.,Hou, H.,Zorba, V.,Russo, R.E.,Jeong, S.H. 한국레이저가공학회 2014 한국레이저가공학회지 Vol.17 No.4
In this work, the application of laser induced breakdown spectroscopy (LIBS) for the composition analysis of thin $Cu(In,Ga)Se_2$ (CIGS) solar cell films ($1-2{\mu}m$ thickness) is reported. For the ablation of CIGS films, femtosecond (fs) laser (wavelength = 343nm, pulse width = 500fs) and nanosecond (ns) laser (wavelength = 266nm, pulse width = 5ns) were used under atmospheric environment. The emission spectra were detected with an intensified charge coupled device (ICCD) spectrometer and multichannel CCD spectrometer for fs-LIBS and ns-LIBS, respectively. The calibration curves for fs-LIBS and ns-LIBS intensity ratios of Ga/Cu, In/Cu, and Ga/In were generated with respect to the concentration ratios measured by inductively coupled plasma optical emission spectrometry (ICP-OES).
이석희(S. H. Lee),조한석(H. S. Cho),허종규(J. K. Heo),이정헌(J. H. Lee),김희국(H. K. Kim) 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.10월
In this study, a car-door-controlled collision protection system using proximity sensor is proposed and its preliminary analysis and several preliminary experiments are conducted. The proposed system has three additional sub-components on the car-door : that is, a pair of extra electro-magnetic actuator that are attached to the sliding bar of the open/close car-door four-bar mechanism, a proximity sensor that would be attached to the outside surface of the door which is likely to frequently contact to the object and a driving control circuit of the whole system. A proximity sensor is used to detect object close to the car-door, the driving control circuit provides actuating power command to the electro-magnets to generate braking force to stop the swing motion of the car-door. It is verified through kinematic analysis of the four-bar car-door open/close mechanism and through experiments that the magnitude of maximum electronic magnetic force could provide the braking force enough for this application. For this purpose, an electro-magnet driving circuit is implemented and tested. And also to increase the safety of the system a time delay circuit is implemented and tested.
스튜워트 플랫폼 구조를 이용한 병진 3-자유도 병렬 메커니즘의 기구학 특성 분석
이석희(S. H. Lee),김희국(W. K. Kim),이병주(B. J. Yi) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월
A novel translational 3-dof parallel mechanism is proposed and analyzed. The mechanism consists of three RRPS serial subchains and an additional passive 3-dof PPP type serial subchain. Three RRPS serial subchains alone may form a structure of the 6-DOF Stewart Platform mechanism. However, in the proposed mechanism, an additional passive serial subchain acts as constraints to restrict the output motion of the mechanism in 3-DOF translational space. The closed form position solutions of the proposed mechanism and its first-order kinematic model are derived. Then its workspace size and kinematic characteristics are examined via kinematic isotropic index.
커플링제가 플라스틱 페라이트 자석의 레올로지와 자기특성에 미치는 영향
이석희(S. H. Lee),최준환(J. W. Choi),문탁진(T. J. Moon),정원용(W. Y. Jeung) 한국자기학회 1998 韓國磁氣學會誌 Vol.8 No.5
Effects of coupling agents on the rheological and magnetic properties of plastic ferrite magnets were investigated. Magnetic powder used was Sr-ferrite, and binder used was polypropylene (PP), and coupling agents used were γ-methacryloxypropyl trimethoxy silane (A174) and isopropyl triisostearoyl titanate (TTS). It was found that the addition of coupling agents to the PP / ferrite system reduced the melt viscosity and increased the magnetic properties considerably, and the treatment with TTS showed greater effect than A174 did. By comparison with that of the untreated one, the apparent viscosities of the mixtures treated with A174 and TTS decreased 23 % and 50 %, respectively, at the shear rate of 1280 sec-¹. Untreated plastic magnets showed remanent flux density (Br) of 1.89 kG and maximum energy product (BHmax) of 0.84 MGOe, and A174 treated magnets showed of Br 2.25 kG and BH(max) of 1.23 MGOe. TTS treated magnets showed Br of 2.35 kG and BH(max) of 1.33 MGOe.
우수한 기구학 특성을 가지는 새로운 병렬형 구형 3자유도 메커니즘의 구현
이석희(S. H. Lee),김희국(W. K. Kim),오세민(S. M. Oh),이병주(B. J. Yi) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월
In our pervious paper, a new parallel-type spherical 3-degree-of-freedom mechanism consisting of a two-degree-of-freedom parallel module and a serial RRR subchain was proposed[1]. In this paper, its improved version is suggested and implemented. Differently from the previous 3-dof spherical mechanism, gear chains are incorporated into the current version of the mechanism to drive the distal revolute joint of the serial subchain from the base of the mechanism and in fact, the modification significantly improves kinematic characteristics of the mechanism within its workspace. Firstly, after a brief description on its structure, the closed-form solutions of both the forward and the reverse position analysis are derived. Secondly, the first-order kinematic model of the mechanism for the inputs which are assumed to be located at the base is derived. Thirdly, through the simulations of the kinematic analysis via. kinematic isotropic index, it is confirmed that the mechanism has much more improved isotropic properties throughout the workspace of the mechanism than the previous mechanism in [1]. Lastly, the proposed mechanism is implemented to verify the results from this analysis.