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눈 비유 모형을 활용한 소집단 활동에서 나타나는 중학생들의 시스템 사고 탐색
황윤식 ( Yoon-sik Hwang ),한문현 ( Moonhyun Han ),김희백 ( Heui-baik Kim ) 韓國生物敎育學會 2016 생물교육 Vol.44 No.4
This study explored how an analogy model activity and teacher supports enhanced students` system thinking and their understanding of the seeing process. Fifty-three 8th grade students used analogy models to learn the structure of the eyes and the seeing process. This study identified three groups of distinct system thinking. Students in the first group focused only on a single sub-structural element of a visual system and did not connect this element to visual system processes. The second group connected the limited sub-structural elements to the processes within a visual system, and students` fragmented ideas led to an alternative conception of the seeing process. The final group explained how visual systems form and interpret images by elaboratively connecting the sub-structural elements to the processes. In addition, by providing concrete scaffolds, the teacher helped students overcome difficulties in their system thinking. This study discussed the implication for using the analogy models as a cognitive tool for facilitating students` system thinking in science classes.
전기자전거 구동 모터의 극/슬롯 비율 조합을 통한 코깅 토크 저감 설계
황윤식(Yunsik Hwang),이남일(Namil Lee),장재덕(Jaeduk Jang),주인식(Insik Joo) 한국자동차공학회 2011 한국자동차공학회 지부 학술대회 논문집 Vol.2011 No.4
Recently, Electric bike is being spotlighted because that is environmentally friendly forms of transport with low noise, low pollution as well as convenience for use. BLOC Motor mainly used for electric bike due to high efficiency and high torque characteristics. But, The structure of BLOC motor produces vibration and cogging torque because of reluctance according to rotating the rotor. The cogging torque is caused by unbalance torque according to permanent magnet in a motor. As a result, it is difficult to ride electric bike comfortably because of vibration, noise. For these reasons, The motor for electric bike must have low cogging torque characteristic design. This paper compared the effect of pole/slot combination on the cogging torque and back-emf waveform between conventional and new models which are analyzed by FEM(Finite Element Method).
전기자전거 구동 모터의 극/슬롯 비율 조합을 통한 코깅 토크 저감 설계
황윤식(Yunsik Hwang),이남일(Namil Lee),장재덕(Jaeduk Jang),주인식(Insik Joo) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.4
Recently, Electric bike is being spotlighted because that is environmentally friendly forms of transport with low noise, low pollution as well as convenience for use. BLDC Motor mainly used for electric bike due to high efficiency and high torque characteristics. But, The structure of BLDC motor produces vibration and cogging torque because of reluctance according to rotating the rotor. The cogging torque is caused by unbalance torque according to permanent magnet in a motor. As a result, it is difficult to ride electric bike comfortably because of vibration, noise. For these reasons. The motor for electric bike must have low cogging torque characteristic design. This paper compared the effect of pole/slot combination on the cogging torque and back-emf waveform between conventional and new models which are analyzed by FEM(Finite Element Method).
고 토크 외전형 인휠 모터의 약계자 제어를 통한 고속 구동 연구
황윤식(Yunsik Hwang),김준성(Junsung kim),장재덕(Jaeduk Jang),주인식(Insik Joo) 한국자동차공학회 2012 한국자동차공학회 지부 학술대회 논문집 Vol.2012 No.4
The paper presents the high-speed drive control of high torque outer rotor in-wheel type BLDC motor for E-bike through the flux weakening control. SPMSM and IPMSM are designed in two ways. The current and the current phase angle according to the inductance Ld, Lq be calculated through FLVM(Flux Linkage Vector Method). High torque BLDC motor designed to minimize current consumption and to enable high speed on flat ground. The torque, speed are calculated using d-q axis equivalent circuit simulation according to the current and the current phase angle. Finally of high-speed driving is verified by analyzing the simulation results of the field weakening control.
시각 개념을 다루는 중학교 과학 교과서에서 시각자료의 시스템 사고 지원 가능성 탐색
황윤식 ( Yoon-sik Hwang ),김희백 ( Heui-baik Kim ) 한국생물교육학회 2017 생물교육 Vol.45 No.3
This study explored how middle school science textbooks facilitated system thinking while addressing visual concepts. This study investigated the system thinking revealed in the text of textbooks, the ontological category of inscriptions and a comparison of the information in the text and the inscriptions. The textbooks addressed visual concepts using three themes: ‘Structure of the eye and vision formation’, ‘Pupillary reflex and visual accommodation’ and ‘Myopia and hyperopia’. A high-level of system thinking was required to learn these visual concepts. Unmodified inscriptions are typically categorized as ‘structure’, but inscriptions can be modified through the addition of words and conventions or the use of multiple images to fit ‘process’. Theses inscriptions could enable to support the high-level system thinking revealed in the text. This study discussed the implication of using inscriptions in a textbook to support system thinking in science classes.
반응성 마그네트론 스퍼터링법에 의한 Nickel Oxide 박막 제작 특성에 관한 연구
김기범,황윤식,김영식,박장식,Kim, Gi-Bum,Hwang, Yun-Sik,Kim, Yeung-Shik,Park, Jang-Sick 한국반도체디스플레이기술학회 2008 반도체디스플레이기술학회지 Vol.7 No.1
In this paper, the DE(double erosion) cathode for the reactive magnetron sputtering system is developed for high deposition rate and high target utilization efficiency. The utilization efficiency of the developed DE cathode is 22% higher than that of normal SE(single erosion) cathode. Sputtering process for the nickel oxide thin films with the DE cathode is performed under the following conditions; power with $1kW{\sim}3kW$, pressure with 4mtorr and 8mtorr, oxygen flow ratio with $0%{\sim}80%$. As a result, the hysteresis phenomenon of discharge voltage in 4mtorr is lower than that in 8mtorr and the hysteresis phenomenon of discharge voltage is getting lower as the applied power is getting higher. The structure of cross section and surface roughness of the thin films are observed by FE-SEM and AFM. The structure of cross section of the thin films is columnar and the average surface roughness under oxygen flow ratio of 0%, 52.5% and 65.0% are $2.08{\AA}$, $2.20{\AA}$ and $0.854{\AA}$, respectively.