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PACKING DIMENSIONS OF GENERALIZED RANDOM MORAN SETS
XinTong,Yue-li Yu,Xiao-jun Zhao 대한수학회 2014 대한수학회지 Vol.51 No.5
We consider random fractal sets with random recursive constructions in which the contracting vectors have different distributions at different stages. We prove that the random fractal associated with such construction has a constant packing dimension almost surely and give an explicit formula to determine it. We consider random fractal sets with random recursive con- structions in which the contracting vectors have different distributions at different stages. We prove that the random fractal associated with such construction has a constant packing dimension almost surely and give an explicit formula to determine it.
Influence of micro-textured parameters on cutting performance and chip formation of milling Ti6Al4V
Xin Tong,Song Yu 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.9
In view of the lack of researches on the influence of micro textures on the cutting performance of milling cutters, this paper studies the cutting performance of the micro-textured ball-end milling cutter, taking the distance from the cutting edge and the offset angle as the influencing factors, and through the comparative test with non-texture cutters, studies the cutting performance and formation of the chip. The results showed that when micro textures are close to the cutting edge, the milling force is larger, while the offset angle had no significant effects on the milling force. The optimized micro-textured parameters are 120 μm and 0.3°. Compared with the non-texture cutter, the micro-textured cutter had better effects of anti-wear and anti-friction, as well as surface quality of the workpiece. The deformation is more serious when the chip passes the rake face. This paper has some guiding significance for the preliminary design of micro-textured cutters.
Influence of the axial radius of rigid arc-shaped rollers in 3D surface rolling
Xintong Wang,Ming-Zhe Li,Yuwei Liu,Xiang Chang,Weifeng Yang 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.8
The research and development of flexible forming technology have a crucial role in the personalized production and manufacturing of three-dimensional (3D) surface sheet metal parts. Three-dimensional surface rolling with rigid arc-shaped rollers (TSRRAR), a new flexible forming technology, was investigated to effortlessly produce 3D surface parts. Numerical simulation and experimental analysis mainly include data at four values of the difference in axial radius of roller (-2, 2, 6 and 10 mm) to explore this technology’s forming ability. It was demonstrated that various shapes could be obtained only based on one group of rollers. The maximum resultant force decreased from 3.07 to 2.21 KN, and the required maximum compression rate from 4.22 to 2.48 % with the same longitudinal curvature radius (179 mm) to be obtained. Therefore, the forming difficulty can be reduced by selecting the difference in axial radius of roller.
Zhu, Xintong,Chen, Zhangyong,Chen, Yong,Chen, Gen,Feng, Chenchen The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.9
In recent years, resonant converters have been widely used in the fields of electric vehicles and renewable energy systems due to their excellent characteristics in terms of high energy density, high energy efficiency, wide output range, and wide ZVS range. Conventional resonant converters generally adopt pulse frequency modulation (PFM) in a wide range of output applications. This means the frequency varies over a wide range, which results in problems such as high switch loss, large noise, and high EMI. To solve this problem, this paper proposes a hybrid fixed-frequency modulation strategy applied to a wide range of outputs based on the series resonant converter, where asymmetrical voltage-cancellation control (AVC control) and its improved strategy (IAVC control) are applied in the normalized gain ranges of [0.5, 1] and [0, 0.5]. The proposed modulation strategy achieves lower switching loss, higher efficiency, and better ZVS characteristics in wide voltage output and load ranges. Under the same output voltage and power, to realize ZVS, the proposed hybrid modulation has a smaller switching frequency and resonant current, which improves efficiency and reduce losses, especially in the case of low voltage gain and light load conditions. Finally, experimental data obtained from an 80 V input and a 800 W power max prototype circuit are included to verify the proposed hybrid modulation strategy.