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Nonlinear dynamic analysis of a vertical rotor-bearing system
Minglin Shi 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.1
Nonlinear dynamic model of a vertical rotor-bearing system is developed based on nonlinear bearing forces. Nonlinear dynamic behaviors are studied comprehensively through numerical analyses, such as bifurcation diagrams, waterfall diagrams, rotor center orbits, Poincare maps, and frequency spectrums. Factors which affect those behaviors, including structural arrangement, rotor mass unbalance, clearance and length of bearing, are investigated as well. Analytical results show that, in vertical arrangement, period doubling bifurcation occurs in advance and the system stability decreases dramatically. When the rotor motion becomes unstable, vertical rotor-bearing system generates sub-synchronous vibrations that are much lower than half-frequency component (0.5x). The stability of vertical rotorbearing system increases with the increases in rotor mass unbalance and bearing length, but it decreases with the increase in bearing clearance.
Rongzhen Jiang,Yincheng Teng,Yajuan Huang,Jinghong Gu,Li Ma,Minglin Shi,Yuedi Zhou 생화학분자생물학회 2014 Experimental and molecular medicine Vol.46 No.-
In women with preeclampsia (PE), endothelial cell (EC) dysfunction can lead to altered secretion of paracrine factors that induce peripheral vasoconstriction and proteinuria. This study examined the hypothesis that PE sera may directly or indirectly, through human umbilical vein ECs (HUVECs), stimulate phospholipase C-γ1-1,4,5-trisphosphate (PLC-γ1-IP3) signaling, thereby increasing protein kinase C-α (PKC-α) activity, collagen I expression and intracellular Ca2+ concentrations ([Ca2+]i) in human umbilical artery smooth muscle cells (HUASMCs). HUASMCs and HUVECs were cocultured with normal or PE sera before PLC-γ1 silencing. Increased PLC-γ1 and IP3 receptor (IP3R) phosphorylation was observed in cocultured HUASMCs stimulatedwith PE sera (Po0.05). In addition, PE serum significantly increased HUASMC viability and reduced their apoptosis (Po0.05); these effects were abrogated with PLC-γ1 silencing. Compared with normal sera, PE sera increased [Ca2+]i in cocultured HUASMCs (Po0.05), which was inhibited by PLC-γ1 and IP3R silencing. Finally, PE sera-induced PKC-α activity and collagen I expression was inhibited by PLC-γ1 small interfering RNA (siRNA) (Po0.05). These results suggest that vasoactive substances in the PE serum may induce deposition in the extracellular matrix through the activation of PLC-γ1, which may in turn result in thickening and hardening of the placental vascular wall, placental blood supply shortage, fetal hypoxia–ischemia and intrauterine growth retardation or intrauterine fetal death. PE sera increased [Ca2+]i and induced PKC-α activation and collagen I expression in cocultured HUASMCs via the PLC-γ1 pathway.