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레이저 피닝 처리를 위한 10J/10㎐ split disk 레이저 개발
임창환(Changhwan Lim) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4
레이저 피닝에 사용하기 위하여 split disk 형태의 레이저를 제작하였으며 제작된 레이저의 냉각매질 유량에 따른 파면왜곡, 소신호 이득을 측정하였다. 냉각매질의 유량이 30L/min일 때도 파면왜곡이 없었으며, 소신호 이득은 매질의 중심부에서 3이상을 얻을 수 있었다. 측정된 매질의 유량과 소신호 이득으로부터 1 J 레이저를 발진기로 사용할 경우 10J/10㎐ 레이저 증폭이 가능할 것으로 예상된다.
Lim, Heonyoung,Kang, Yeonsik,Kim, Changhwan,Kim, Jongwon 한국정밀공학회 2014 International Journal of Precision Engineering and Vol.15 No.5
This paper presents a nonlinear model predictive tracking control scheme for a six-wheeled nonholonomic unmanned ground vehicles (UGVs). It is employed as a high-level guidance control with kinematic approximation for UGV motion. A nonlinear model predictive control algorithm solves trajectory planning and optimal control problems by sequentially solving an online numerical optimization problem. The optimal control inputs for the UGV are obtained with a gradient descent optimization algorithm considering constraints of UGV motion as well as its input constraints. The characteristics of the proposed controller in terms of tracking performance and collision avoidance were investigated. The real-time performance of the proposed numerical optimization algorithm was verified with an experimental six-wheeled UGV platform in indoor and outdoor environments.
Lim, Donghwan,Lee, Jae Ho,Choi, Changhwan Elsevier 2017 MICROELECTRONIC ENGINEERING Vol.178 No.-
<P><B>Abstract</B></P> <P>We have studied the electrical characteristics of both n-type and p-type fully depleted silicon on insulator (FD-SOI) tunnel field-effect transistors (TFETs) by modulating Al<SUB>2</SUB>O<SUB>3</SUB> fraction (25%, 50%) within atomic layer deposited HfAlO<SUB>x</SUB> gate dielectric. Compared to HfO<SUB>2</SUB> alone, lower subthreshold swing (S.S), higher I<SUB>on</SUB>/I<SUB>off</SUB>, and stronger threshold voltage (V<SUB>th</SUB>) immunity against electrical stress are obtained for both n-type and p-type TFETs by adopting nano-laminated atomic layer deposited HfAlO<SUB>x</SUB>, attributed to the increased band gap and interfacial layer scavenging effect.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Compared to HfO<SUB>2</SUB>-TFET, HfAlO<SUB>x</SUB>-TFET show lower S.S, higher I<SUB>on</SUB>/I<SUB>off</SUB>, and improved BTI characteristics. </LI> <LI> HfAlO<SUB>x</SUB> TFET (25% Al composition) shows the optimal electrical characteristics. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
The Post Annealing to Control the Number of Layers of 2D MoS<sub>2</sub> and SnS<sub>2</sub>
Choi, Moonsuk,Lim, Donghwan,Sergeevich, Andrey Sokolov,Son, Seok Ki,Kim, Young Jin,Han, Hoon Hee,Choi, Changhwan American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.11
<P>We have demonstrated that post annealing could control the layer thickness of 2D MoS2 and SnS2 films transferred on a SiO2/Si substrate by varying the annealing temperature and time. Atomic force microscopy and Raman spectroscopy characterizations revealed that higher annealing temperature and longer treatment time led to thinner films, lower residues and fewer impurities on the surface of 2D materials. In addition, a higher possibility to attain few-layers on both 2D films was achieved using post annealing. The multiple layers of pristine films having the thickness over 15 nm were reduced down to bi-layers after annealing. We observed that the moderate annealing temperature of 450 degrees C on led to effective layer-thinning compared to the films annealed at 340 degrees C. The post annealing at 450 degrees C produced very smooth few-layers (<= 4 nm thickness, >1 mu m size) of 2D MoS2 and SnS2. However, the 2D films decomposed or disappeared at temperature greater than 650 degrees C. In addition, process time also affected the number of layers and the sweet spot turned out to be 2 to 3 hours in our experiment.</P>