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Synthesis of TiO<sub>2</sub> Nanotubes and Their Sensitivity for Toluene Gas
Yue, H.Y.,Huang, S.,Guo, E.J.,Wang, L.P.,Kang, F.W.,Yu, Z.M.,Guo, Y.K.,Sun, F.L. The Korean Powder Metallurgy Institute 2011 한국분말재료학회지 (KPMI) Vol.18 No.1
$TiO_2$ nanopowders with anatase structure were firstly prepared by controlling the pH value of a precursor solution without any heat-treatment at room temperature. The prepared $TiO_2$ nanopowders were hydrothermally treated in 10M NaOH solution at $170^{\circ}C$. Then, the samples were washed in DI water or 0.1M HCl. The $TiO_2$ nanotubes were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The gas sensitivity of $TiO_2$ nanotubes for toluene gas was also investigated. The results show that $TiO_2$ nanotubes can be prepared by hydrothermal treatment. The morphology of $TiO_2$ nanotubes prepared by 0.1M HCl washing is destroyed to some extent. $TiO_2$ nanotubes with DI water washing show better sensitivity than that with 0.1M HCl washing.
김주완(Juwan Kim),장인성(Insung Jang) 대한공간정보학회 2021 한국공간정보학회 학술대회 Vol.2021 No.11
스마트시티, 디지털트윈 등 실감형 3D 도시모델에 대한 수요가 증가하면서, UAV 기반 고품질 항공 영상에 대한 요구가 커지고 있다. 그러나, 도심지 영상에 포함된 건물 그림자는 영상 처리, 시뮬레이션 등의 활용 과정에서 장애 요소로 작용하고 있다. 본 연구는 UAV로 촬영한 도심지 항공 영상에 있는 그림자를 딥러닝으로 제거하여 화질을 개선하는 방법을 제안한다. 제안 방법은 개선된 이중 계층적 그림자 제거 인공신경망을 기반으로 다양한 실세계 환경에 강건한 그림자 제거 성능을 확보하기 위하여 물리적 조명 모델을 활용한 도메인 랜덤화 기법을 적용하였다. 공개된 학습 데이타를 이용하여 성능 평가를 실시하였으며, 실제 드론 촬영 영상에 적용하여 그림자 영역의 화질이 개선된 결과를 제시한다.
Electrical Resistivity and Demagnetization Characteristics of Salt-added Nd-Fe-B-type Magnet
M. S. Kang,K. M. Kim,H. W. Kwon,D. Wu,M. Yue,M. C. Kang,C. W. Yang,D. H. Kim,J. G. Lee,J. H. Yu 한국자기학회 2019 Journal of Magnetics Vol.24 No.3
Nd-Fe-B-type die-upset magnet with high electrical resistivity was fabricated by hot-deforming the mixture of melt-spun Nd-Fe-B-type flakes (MQU-F: Nd13.6Fe73.6Co6.6Ga0.6B5.6) and Dy-containing salts: eutectic (DyF₃–LiF) salt mixture and DyF₃ single salt. Profound electrical resistivity enhancement was feasible in the Nd-Fe-B-type die-upset magnet by adding Dy-containing salts. More profound electrical resistivity enhancement was achieved in the magnet added with dielectric eutectic (DyF₃–LiF) salt mixture with respect to the magnet added with single DyF₃ salt. This was attributed to better electrical insulation between the flakes by forming more continuous coverage of the flake interface with the easily melted dielectric salt. Coercivity of the die-upset magnet was also profoundly enhanced by optimal addition of Dy-containing salts, and this was attributed to substitution of some Nd in the Nd₂Fe14B-type grains near flake surface by Dy atoms from the added salt. Kerr microscopy revealed that for both the magnets with or without salt addition, formation of reverse domain initiated mostly inside the flake. Reversed domain started to form at higher reverse field for the magnet added with Dy-containing salt than for the magnet without salt addition. Practical demagnetization occurred largely by formation of new reverse domains at random places rather than enlargement of previously formed reverse domain for both the magnets with or without salt addition.
W. Q. Liu,C. Chang,M. Yue,J. S. Yang,D. T. Zhang,Y. Q. Liu,J. X. Zhang,X. F. Yi,J. W. Chen 한국자기학회 2013 Journal of Magnetics Vol.18 No.4
Grain boundary diffusion technique with DyH₃ nanoparticles was applied to fabricate Dy-less sintered Nd-Fe-B permanent magnets with high coercivity. The magnetic properties and microstructure of magnets were systematically studied. The coercivity and remanence of grain boundary diffusion magnet were improved by 60% and reduced by 7% compared with those of the original magnet, respectively. Meanwhile, both the remanence temperature coefficient (α) and the coercivity temperature coefficient (β) of the magnets were improved after diffusion treatment. Investigation shows that Dy is preferentially enriched as (Nd, Dy)₂Fe14B phase in the surface region of the Nd₂Fe14B matrix grains indicated by the remarkable enhancement of the magneto-crystalline anisotropy field of the magnet. As a result, the magnet diffused with a small amount of Dy nanoparticles possesses enhanced coercivity without remarkably sacrificing its magnetization.
Y. Q. Li,M. Yue,J. H. Zuo,D. T. Zhang,W. Q. Liu,J. X. Zhang,Z. H. Guo,W. Li 한국자기학회 2013 Journal of Magnetics Vol.18 No.3
A finite element model was built for MnBi/α-Fe nanocomposite permanent magnets, and the demagnetization curves of the magnets were simulated by micro-magnetic calculation. The microstructure of the cubic model is composed of 64 irregular grains with an average grain size of 20 nm. With the volume fraction of soft magnetic phase (t vol. %) ranged from 5 to 20 vol. %, both isotropic and anisotropic nanocomposite magnets show typical single-phase permanent magnets behavior in their demagnetization curves, illustrating good intergranular exchange coupling effect between soft and hard magnetic phases. With the increase of volume fraction of soft magnetic phase in both isotropic and anisotropic magnets, the coercive force of the magnets decreases monotonically, while the remanence rises at first to a peak value, then decreases. The optimal values of maximum energy products of isotropic and anisotropic magnets are 84 and 200 kJ/m3, respectively. Our simulation shows that the MnBi/α-Fe nanocomposite permanent magnets own excellent magnetic properties and therefore good potential for practical applications.
L. Pu,W. Yue,C. Wulong,L. Wanjun 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Modular Multilevel Converter (MMC) is a promising topology for high voltage/power AC/DC and DC/AC applications. Model Predictive Control (MPC) is an advanced and simple method for power converters control. However, its computational load becomes unacceptable when MMC voltage level increases. Although an optimized MPC proposed for the MMC decreased the number of the possible actuations of each phase from Cⁿ2N to N+1 for N+1 levels MMC, which is still difficult for application as the number of submodule for each arm reached hundreds. The Grouping-Sorting algorithm optimized MPC (GSOMPC) is proposed in the paper. The submodule capacitor voltages within the group and among groups are sorted according to the arm current polarity, the proposed GSOMPC decreased the number of the possible actuations of each phase from N+1 to 2X+M+3 (N=M×X) for N+1 levels MMC. The simulation and experimental results based on 25-level MMC verify the correctness and effectiveness of the GSOMPC strategy.