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Magnetic circular dichroism measurement of Co films on Pd(111) substrate
Kwanghyun Cho,C. N. Whang,Wookje Kim,Wondong Kim,H.-J. Kim,Jae-Young Kim,Hoon Koh,S. J. Oh,J.-H. Park 한국진공학회(ASCT) 2001 Journal of Korean Vacuum Science & Technology Vol.5 No.2
We measured x-ray magnetic circular dichroism of Co films on Pd(111) surface with and without Pd capping layer at the Co L₂,₃ edges. Perpendicular magnetization and orbital-moment enhancement are induced by the capping layer.<br/> The increase of perpendicular magnetic anisotropy induced by capping layer is considered to result from the increase of surface anisotropy due to the hybridization at the surface.
A High-Precision Motion Control Based on a Periodic Adaptive Disturbance Observer in a PMLSM
Kwanghyun Cho,Jonghwa Kim,Seibum Ben Choi,Sehoon Oh IEEE 2015 IEEE/ASME Transactions on Mechatronics Vol.20 No.5
<P>This paper presents a novel disturbance compensation scheme to attenuate periodic disturbances on repetitive motion using permanent magnet linear synchronous motors (PMLSMs), and this scheme is called the periodical adaptive disturbance observer. The scheme is based on assumptions that all measured states and disturbances are periodic and repetitive when the tasks executed by PMLSM motion systems have periodic and repetitive characteristics. In the proposed control scheme, a lumped disturbance is estimated by the classical linear disturbance observer (DOB) for the initial time period and stored in memory storages. It consists of parametric errors multiplied by states, friction force, and force ripple, and then, it is updated for each time period by the periodic adaptation law. This scheme requires no mathematical models of disturbances and adaptation laws of model parameters such as the mass of the mover and viscous friction coefficient. Also, it is possible to compensate for disturbances above as well as below the bandwidth of the Q-filter (LPF) of DOB. The effectiveness of the proposed control scheme is verified by various experiments that take into account varying frequency components of disturbances along the operating speed of a mover of PMLSM such as force ripple and friction force.</P>
Analysis of seasonal effect on Korean native cattle (Hanwoo) birth weight
( Kwanghyun Cho ),( Yirim Song ),( Joon-mo Yeo ),( Jin-Ki Park ),( Dong-Wook Kim ),( Seung-Hee Roh ),( Pilnam Seong ),( Won-Young Lee ) 한국축산학회(구 한국동물자원과학회) 2021 한국축산학회지 Vol.63 No.4
Recently, summer temperatures have frequently been abnormal in Korea owing to global warming. In summer, a decrease in feed intake rate and biological activity were observed in Hanwoo (Korean Native Cattle), leading to lower production rates in the industry. However, the precise scale of damage was not reported as with other animals of economic value. This study was conducted to investigate the effects of birth season on birth weight in Hanwoo. Data were collected from 100 local breeding farms from 2016 to 2019. A total of 41,081 Hanwoo calves were classified and analyzed by sex, year, month, and season (March-May, spring; June-August, summer; September-November, fall; and December-February, winter) of birth. The birth weight of Hanwoo calves differed according to birth month. The average birth weight of male calves was 30.47 kg and that of female calves was 28.16 kg. Hanwoo birth weight was the highest in March-born calves and the lowest in July-born calves. The birth weights of calves born in February, March, April, November, and December were significantly larger than those of calves born in July. In addition, the birth weight of Hanwoo calves from the summer was significantly lower than that of calves born in other seasons. Furthermore, Hanwoo steer slaughter age showed a negative correlation, whereas carcass weight had a positive correlation with birth weight. In the beef cattle industry, birth weight is a very important economic characteristic that is related to growth rate. These data will contribute toward planning the reproduction of Hanwoo and analysis of changes in characteristics of economic value owing to high temperatures.
조광현(Kwanghyun Cho),최세범(Seibum Choi),유주현(Joohyun Ryu),김종갑(Chongkap Kim) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
In this paper, an anti-lock brake system(ABS) algorithm using wheel pressure sensors is proposed. The wheel pressure sensors are used to estimate the road friction coefficient, which sensors are used recently to smart cruise control system and a hybrid car. The road friction coefficient is the most important information to control the vehicle stability. Using the estimated road friction coefficient, the vehicle detects mu-transition situation such as high-to-low mu or low-to-high mu and split-mu situation easily. Also, the performance of the estimation for vehicle states such as vehicle speed and acceleration can be improved. Especially, it is efficient to control the left/right and front/rear wheel independently because the friction coefficient is estimated separately. The simulation has been performed to verify the robustness of the proposed ABS algorithm in a variety of road conditions which has different friction coefficients.
단계적 충돌 유형 구분에 따른 강인한 충돌 알고리즘 설계
조광현(Kwanghyun Cho),최세범(Seibum Choi),강석창(Sukchang Kang),신경재(Kyungjae Shin) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
An airbag system has been a standard safety system for saving a driver’s and passengers’ life after a crash is occurred. But it has several problems that airbags are not deployed though they must be deployed or deployed though they must not be deployed. It can make unpredicted injuries of a driver or passengers. Therefore the role of the crash algorithm to deploy airbags is very important. In this paper, a robust crash algorithm is developed to deploy airbags in a proper time when a crash is occurred. The algorithm discriminates crash types using FIS(Front Impact Sensors) first and revises it using ACU-Y sensor(acceleration sensor of Y-direction in Airbag Control Unit). After then, airbags are deployed along the discriminated crash type. In this algorithm, using the combination of both sensors, the reliability of discriminated crash type information becomes higher than when each sensor is used separately.
정사각형 단면채널에 의한 다중채널 MOSFET의 전기적 특성 개선
조광현(Kwanghyun Cho),김수경(Sukyung Kim),손병일(Byungil Son),정일섭(Ilsub Chung) 한국정보과학회 영남지부 2007 한국정보과학회 영남지부 학술발표논문집 Vol.1 No.1
우리는 3차원 구조의 정사각형 단면 다중채널을 갖는 금속-산화물-반도체소자를 연구하였다. 다중채널의 단면은 게이트의 채널에 대한 제어력을 향상시키기 위하여 정사각형 모양으로 만들어졌다. 우리는 종래의 다중채널을 트랜지스터와 비교하여 정사각형 다중채널을 갖는 트랜지스터의 전기적 특성을 소개한다. 이 트랜지스터는 3차원 구조에서 채널에서 게이트까지의 균일한 거리를 가지기 때문에, 기존의 다중채널 트랜지스터보다 많은 이점이 있을 것이다. 본 논문에서는 3차원 소자 시뮬레이션 프로그램인 아틀라스를 활용하여 채널 단면이 20㎚×20㎚와 10㎚×30㎚인 n타입 다중채널 MOSFET의 Id-Vg(Drain current-Gate voltage), Id-Vd(Drain current-Drain voltage) 특성을 시뮬레이션하였다. 시뮬레이션 결과를 바탕으로 채널이 형성되는 단면의 둘레의 길이는 80nm로 동일하지만 정사각형 단면의 다중채널 MOSFET의 Drain Current가 약 1.3배 증가한 것을 확인하였다. 그리고 채널 길이에 따른 두 소자의 Threshold Voltage, DIBL(Drain Induced Barrier Lowering)과 SS(Subthreshold Swing) 그리고 Mobility를 측정해본 결과, 정사각형 단면의 다중채널 MOSFET의 성능이 개선되었다.