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Ran Zhao,Bowen Wang,Shuying Cao,Wenmei Huang,Quanguo Lu,Jianwu Yan 한국자기학회 2018 Journal of Magnetics Vol.23 No.2
In this paper, we fabricated novel magnetostrictive composites by embedding <110>-oriented Tb-Dy-Ho-Fe fibers in an epoxy matrix. The magnetostrictive and magnetic properties (magnetostriction, magnetization, piezomagnetic coefficient and relative permeability) of the proposed composites were measured, analyzed, and compared to those of Tb0.29Dy0.48Ho0.23Fe1.9 alloy and Tb0.3Dy0.7Fe₂ continuous-fiber/epoxy composites. Tb0.29Dy0.48Ho0.23Fe1.9 continuous-fiber/epoxy composites have a saturation magnetostriction (λs) of 840 ppm and saturation magnetization (Ms) of 0.75 T. Their piezomagnetic coefficient exhibits a maximum value (8.2 μm/kA) at 19 kA/m. These proposed composites exhibit a large magnetostriction in high magnetic fields (> 400 kA/m) and a large relative permeability in low magnetic fields (< 100 kA/m). This result indicates that the given composites perform better than the Tb0.29Dy0.48Ho0.23Fe1.9 alloy and Tb0.3Dy0.7Fe₂ fiber/epoxy composites. Thus, the composites with characteristics of high sensitivity and large magnetostriction can be used in the field of ultrasonic sensing.
Yang Qu,Rongpeng Dong,Mingyang Kang,Jianwu Zhao 한국조직공학과 재생의학회 2015 조직공학과 재생의학 Vol.12 No.3
We wanted to know whether K-ROD (KD) internal fixation system could ameliorate lumbar adjacent segment degeneration (LASD) diseases. From May 2010 to May 2012, 66 patients with lumbar LASD were repaired via KD system. The outcome for LASD was analyzed using visual analogue scale (VAS), Oswestry disability index (ODI) and the 36-Item Short Form Health Survey. Meanwhile, range of motion (ROM) of total lumbar and dynamic fixation segments were also examined. Twelve patients inquired the removal of KD system because of fatigue during the first year after surgery. For remaining patients, the mean VAS score for back pain was 45.2±28.7 before operation, and decreased to 22.3±14.2 after two-year surgery (p<0.01); meanwhile, the mean ODI score was decreased from 76.5±11.2% to 21.1±5.4% (p<0.01). SF-36 parameters were significantly improved compared with those acquired the removal of KD system (p<0.01). Total 45 patients restored flexion-extension ROM after surgery (p<0.01). More than 80% disc generation was improved by KD system. KD system is an effective therapeutic way for treating LASD patients. The dynamic stabilization system preserves the motion of fixation segment and provides an alternative for therapy of lumbar LASD.
Resonance Characteristics Analysis of Grid-connected Inverter Systems based on Sensitivity Theory
Jian Wu,Wanqin Han,Tao Chen,Jiaqi Zhao,Binbin Li,Dianguo Xu 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.3
Harmonic resonance exists in grid-connected inverter systems. In order to determine the network components that contribute to harmonic resonance and the composition of the resonant circuit, sensitivity theory is applied to the resonance characteristic analysis. Based on the modal analysis, the theory of sensitivity is applied to derive a formula for determining the sensitivities of each network component parameter under a resonance circumstance that reflects the participation of the network component. The solving formula is derived for both parallel harmonic resonance and series harmonic resonance. This formula is adopted to a 4-node grid-connected test system. The analysis results reveal that for a certain frequency, the participation of parallel resonance and series resonance are not the same. Finally, experimental results demonstrate that the solving formula for sensitivity is feasible for grid-connected systems.
Jian Wu,Tao Chen,Wanqin Han,Jiaqi Zhao,Binbin Li,Dianguo Xu 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1
Interaction among multiple grid-connected inverters has a negative impact on the stable operations and power quality of a power grid. The interrelated influences of inverter inductor–capacitor–inductor filters constitute a high-order power network, and consequently, excite complex resonances at various frequencies. This study first establishes a micro-grid admittance matrix, in which inverters use deadbeat control. Multiple resonances can then be evaluated via modal analysis. For the active damping method applied to deadbeat control, the sampling frequency and the stable domain of the virtual damping ratio are also presented by analyzing system stability in the discrete domain. Simulation and experimental results confirm the efficiency of modal analysis and stable domain calculation in multi-inverter grid-connected systems.