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Research of the Mechanism of Low Frequency Oscillation Based on Dynamic Damping Effect
Wenying Liu,Rundong Ge,Dandan Zhu,Weizhou Wang,Wei Zheng,Fuchao Liu 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.4
For now, there are some low frequency oscillations in the power system which feature low frequency oscillation with positive damping and cannot be explained by traditional low frequency oscillation mechanisms. Concerning this issue, the dynamic damping effect is put forward on the basis of the power-angle curve and the study of damping torque in this article. That is, in the process of oscillation, damping will dynamically change and will be less than that of the stable operating point especially when the angle of the stable operating point and the oscillation amplitude are large. In a situation with weak damping, the damping may turn negative when the oscillation amplitude increases to a certain extent, which may result in an amplitude-increasing oscillation. Finally, the simulation of the two-machine two-area system verifies the arguments in this paper which may provide new ideas for the analysis and control of some unclear low frequency phenomena.
Research of the Mechanism of Low Frequency Oscillation Based on Dynamic Damping Effect
Liu, Wenying,Ge, Rundong,Zhu, Dandan,Wang, Weizhou,Zheng, Wei,Liu, Fuchao The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.4
For now, there are some low frequency oscillations in the power system which feature low frequency oscillation with positive damping and cannot be explained by traditional low frequency oscillation mechanisms. Concerning this issue, the dynamic damping effect is put forward on the basis of the power-angle curve and the study of damping torque in this article. That is, in the process of oscillation, damping will dynamically change and will be less than that of the stable operating point especially when the angle of the stable operating point and the oscillation amplitude are large. In a situation with weak damping, the damping may turn negative when the oscillation amplitude increases to a certain extent, which may result in an amplitude-increasing oscillation. Finally, the simulation of the two-machine two-area system verifies the arguments in this paper which may provide new ideas for the analysis and control of some unclear low frequency phenomena.
Haihua Yuan,Bin Jiang,Zhong-Zheng Zhu,Yachao Lu,Feng Liu,Wenying Zhang,Gang Huang,Guanshan Zhu 연세대학교의과대학 2012 Yonsei medical journal Vol.53 No.1
Purpose: Circulating free DNA (cfDNA) in plasma is promising to be a surrogate for tumor tissue DNA. However, not all epidermal growth factor receptor (EGFR) mutations in tumor tissue DNA has been detected in matched cfDNA, at least partly due to inefficient cfDNA extraction method. The purpose of this study was to establish an efficient plasma cfDNA extraction protocol. Materials and Methods: The yield of plasma cfDNA extracted by our modified phenol-chloroform (MPC) method from non-small-cell lung cancer (NSCLC) patients was compared with that by QIAamp MinElute Virus Spin kit (Qiagen kit) as control, using the Wilcoxon rank-sum test. TaqMan quantitative polymerase chain reaction (qPCR) assays were used to quantify the plasma cfDNA extracted. Both Mutant-enriched PCR (ME-PCR) coupled sequencing and DxS EGFR mutation test kit were used to evaluate the impact of extraction method on EGFR mutation analysis. Results: MPC method extracted more plasma cfDNA than Qiagen kit method (p=0.011). The proportion of longer fragment (≥202 bp) in cfDNA extracted by MPC method was significantly higher than by Qiagen kit method (p=0.002). In the sequencing maps of ME-PCR products, a higher mutant peak was observed on plasma cfDNA extracted by MPC method than by Qiagen kit method. In DxS EGFR mutation test kit results, plasma cfDNA extracted by MPC method contained more tumor-origin DNA than by Qiagen kit method. Conclusion: An improved plasma cfDNA extraction method of MPC is provided, which will be beneficial for EGFR mutation analysis for patients with NSCLC.