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김휘준 ( Kyung-sup Kim ),박길섭 ( Hui-joon Kim ),서영학 ( Kil-seop Park ),김경섭 ( Yeong-hak Seo ) 한국정보처리학회 2017 한국정보처리학회 학술대회논문집 Vol.24 No.2
본 논문은 이미지 탐지 모델인 Faster R-CNN 을 통해 영유아가 존재하는 어린이 집, 공원, 놀이터, 거실 등의 2D 이미지를 읽어 영유아에게 위험이 되는 요소를 인식해 위험상황을 감지하는 시스템을 구현하였다. 실생활에서 쉽게 구할 수 있는 데이터를 바탕으로 탐지 모델을 구현 했으며 현재 머신 러닝 분야가 음성인식과 행위데이터를 기반으로 상용화 되어있는 반면 본 모델은 이미지를 데이터로 한 탐지 모델이 다양한 서비스 분야에서 활용 될 수 있음을 보여준다.
Fe계 연자성 합금 분말의 고온 압연시 자성특성에 미치는 압연인자들의 영향
김휘준(H. J. Kim),이주호(J. H. Lee),이성호(S. H. Lee),박은수(E. S. Park),허무영(M. Y. Huh),배정찬(J. C. Bae) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
Iron-based soft magnetic materials are widely used as cores, such as transformer transformers, motors, and generators. Reducing losses generated from soft magnetic materials of these applications results in improving energy conversion efficiency. Recently, the new P/M soft magnetic material realized an energy loss of 68 W/kg with a drive magnetic flux of 1 T, at a frequency of 1 kHz, rivaling general-purpose electromagnetic steel sheet in the low frequency range of 200 Hz to 1 kHz. In this research, the effect of rolling parameters on soft magnetic properties of Fe-based powder cores was investigated. The Fe-based soft magnetic plates were produced by the hot powder rolling process after both pure Fe and Fe-4%Si powders were canned, evacuated, and sealed in Cu can. The soft magnetic properties such as energy loss and coercive power were measured by B-H curve analyzer. The soft magnetic properties of rolled sheets were measured under conditions of a magnetic flux density of 1 T at a frequency of 200 kHz. It was found that rolling reduction ratio is the most effective parameter on reducing both energy loss and coercivity because of increasing aspect ratio with reduction ratio. By increasing aspect ratio from 1 to 9 through hot rolling of pure Fe powder, a significant loss reduction of one-third that of SPS sample was achieved.
희토류 자원문제 해결을 위한 모터 및 영구자석 연구개발 동향
이정구(J. G. Lee),유지훈(J. H. Yu),김휘준(H. J. Kim),장태석(T. S. Jang) 한국자기학회 2012 韓國磁氣學會誌 Vol.22 No.2
Since Nd-Fe-B magnet was first synthesized in 1983, many new applications have emerged in the past two decades. With regard to motor market, it will expand because of strong energy saving requirements from the automobile and electric application markets. Especially, permanent magnet motors for hybrid and electric vehicles are drawing great attention and the usage of Nd-Fe-B magnets will increase all the more hereafter. There is, however, a serious problem as motors in such eco-friendly cars are said to operate in high temperatures of about 200℃. Nd-Fe-B magnet has a drawback of dramatically decreasing coercive force with the rise of temperature. In order to improve this aspect. the best way is to add dysprosium (Dy) into the magnet. So, Dy has become an essential element for Nd-Fe-B high-performance magnet as it helps to maintain coercive force even at high temperatures. On the other hand, the rare earth resources in the earth crust are eccentrically-located and its majority is produced in China. There is a need to reduce its usage as, especially compared to light rare earth elements as neodymium (Nd) and samarium (Sm), heavy rare earth elements including Dy are unevenly distributed to a dramatic degree, their output low, and their prices are about 10 times that of Nd. The present article includes a summary of the trend in research and development of motors and permanent magnets to solve rare-earth resources problem.
가스분무법에 의한 Fe계 비정질 분말의 제조와 볼밀링공정에 의한 연질 Cu분말과의 복합화 및 SPS 거동 (II) - II. 복합분말의 SPS와 특성 -
김진천,김지순,김휘준,김정곤,Kim, Jin-Chun,Kim, Ji-Soon,Kim, H.J.,Kim, Jeong-Gon 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.5
Fe based (Fe$_{68.2}$C$_{5.9}$Si$_{3.5}$B$_{6.7}$P$_{9.6}$Cr$_{2.1}$Mo$_{2.0}$Al$_{2.0}$) amorphous powder, which is a composition of iron blast cast slag, were produced by a gas atomization process, and sequently mixed with ductile Cu powder by a mechanical ball milling process. The Fe-based amorphous powders and the Fe-Cu composite powders were compacted by a spark plasma sintering (SPS) process. Densification of the Fe amorphous-Cu composited powders by spark plasma sintering of was occurred through a plastic deformation of the each amorphous powder and Cu phase. The SPS samples milled by AGO-2 under 500 rpm had the best homogeneity of Cu phase and showed the smallest Cu pool size. Micro-Vickers hardness of the as-SPSed specimens was changed with the milling processes.
가스분무법에 의한 Fe계 비정질 분말의 제조와 볼밀링공정에 의한 연질 Cu 분말과의 복합화 및 SPS 거동 (I) - I. 가스분무 및 복합화 -
류호진,임재현,김지순,김진천,김휘준,Ryu, Ho-Jin,Lim, Jae-Hyun,Kim, Ji-Soon,Kim, Jin-Chun,Kim, H.J. 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.5
Fe based (Fe$_{68.2}$C$_{5.9}$Si$_{3.5}$B$_{6.7}$P$_{9.6}$Cr$_{2.1}$Mo$_{2.0}$Al$_{2.0}$) amorphous powder, which is a composition of iron blast cast slag, were produced by a gas atomization process, and sequently mixed with ductile Cu powder by a mechanical ball milling process. The experiment results show that the as-prepared Fe amorphous powders less than 90 $\mu$m in size has a fully amorphous phase and its weight fraction was about 73.7%. The as-atomized amorphous Fe powders had a complete spherical shape with very clean surface. Differential scanning calorimetric results of the as-atomized Fe powders less than 90 $\mu$m showed that the glass transition, T$_g$, onset crystallization, T$_x$, and super-cooled liquid range $\Delta$T=T$_x$-T$_g$ were 512, 548 and 36$^{\circ}C$, respectively. Fe amorphous powders were mixed and deformed well with 10 wt.% Cu by using AGO-2 high energy ball mill under 500 rpm.