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A ZVS-SVM Method for Grid Inverter with Extended Power Factor Angle
Yuying Wu,Ning He,Dehong Xu 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
Grid inverter is required to generate reactive power to support the power system during grid faults to satisfy the grid code. Therefore the grid inverter should have the ability to operate with wide power factor range. In this paper, a Zero-Voltage-Switching Space Vector Modulation (ZVSSVM) scheme for three-phase ZVS grid inverter with extended power factor angle is proposed. With only one switching operation of the auxiliary switch during one switching period of SVM, ZVS of all switches can be achieved. Stage operations are analyzed and ZVS condition is derived. Finally the proposed ZVS-SVM method is verified by experiments.
Zhe Wu,Yuying Zhang,Yong Liu,Fangli Mo,Chengwu Wang,Huizong Lu,Julong Yuan,Zhifeng Liu 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.25 No.1
Aiming to green machining of single crystal sapphire, polysaccharide-bonded soft abrasive tool using hydrothermal gelatinisation method was proposed. Mechanical properties of prepared polysaccharide films show that when the weight ratio of natural polysaccharide to cross-linked polysaccharide is 1:1, the tensile strength and extension rate of the film are relatively optimal. Composition and making process of polysaccharide bonded abrasive tool was built. Samples of polysaccharide bonded soft abrasive tools were made by which the single crystal sapphire substrates were machined. It is found that by adopting guar gum as dispersion agent and hydrothermal gelatinisation, the abrasive sedimentation during making process of abrasive tool is substantially eliminated, and better abrasive holding ability is attained. XPS and Raman microscope analysis showed that material of single crystal sapphire was removed by mechano-chemical reaction with good surface integrity. Abrasive tools with abrasive to binder ratio of 4:1 presented relatively better self-sharpening and machining performance, and the material removal rate reached 0.427 μm/min. More interesting, XPS and FT-IR analyses both indicated that the polysaccharide binder dehydrated by the friction heat during machining process.
Meng Fanchao,Wu Yuying,Li Wenbo,Hu Kaiqi,Zhao Kai,Yang Huabing,Gao Tong,Sun Yue,Liu Xiangfa 한국물리학회 2022 Current Applied Physics Vol.39 No.-
Evolution of the heat-resistant phases and deformation behavior of α-Al matrix of four alloys have been characterized by SEM and EBSD. The strengthening mechanisms influenced by morphology and distribution of the heat-resistant phases were described. And the strain contouring of the α-Al matrix after deformation was rendered. The heat-resistant phases with block-like as reticular or semi-reticular network distribution exist in grain boundary can effectively provide elevated-temperature strength for alloys, while the strain contouring of α-Al matrix is mainly concentrated in the area with fewer intermetallic phases. It is shown that intermetallic phase evolution corresponds to extrusion treatment and the formation of eutectic Si and primary Si, highly interconnected networks of intermetallic phases exist in the alloy in which the primary Si and the eutectic Si are simultaneously present or disappeared. And only the disappearance of the primary Si and the extrusion treatment will destroy the network structure of the intermetallic phases. A reticular or semi-reticular microstructure is more capable of matching strength and plasticity and facilitating uniform deformation of the α-Al matrix. And the destruction of this microstructure is allowed to accommodate more plastic strain before failure.
Stable Amorphous Bis(diarylamino)biphenyl Derivatives as Hole-Transporting Materials in OLEDs
Zhanfeng Li,Zhaoxin Wu,Wen Fu,Dongdong Wang,Peng Liu,Bo Jiao,Xiaoli Lei,Guijiang Zhou,Yuying Hao 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.5
Stable bis(diarylamino)biphenyl derivatives N4,N4'-di(biphenyl-4-yl)-N4,N4'-bis(2- methylbiphenyl-4-yl)biphenyl-4,4'-diamine (TPD-Ph) and N4,N4'-bis(2',4'-difluoro- 2-methylbiphenyl-4-yl)-N4,N4'-bis(2',4'-difluorobiphenyl-4-yl)biphenyl-4,4'-diamine (TPD-(2,4)-F) were synthesized and characterized. High thermal stability (Td ≥ 480°C and Tg ≥ 108°C) in combination with reversible oxidation process render the both promising candidates as hole-transporting materials for organic light-emitting devices. The device with structure of ITO/TPD-Ph/Alq3/LiF/Al presented the highest current efficiency of 4.2 cd A−1 and good operational stability even under the high current density of 350 mA cm−2, which outperformed TPD or NPB-based devices.