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Articles by Ming Xu
Total Records ( 5 ) for Ming Xu
  Luobei Kuang , Zhijun Wang , Ming Xu and Yingwen Chen
  Vehicular networks are becoming an important way to provide various services. As the broadcast is highly used in vehicular networks, there is a need to study the performance of the broadcast protocols. This study aims to investigate the IEEE 802.11 broadcast protocol performance in the highly mobile vehicular network environments. In this study, we firstly propose a zone based system model to catch up the vehicle mobility and then develop performance models based on analysis of vehicle DCF broadcast behaviors. Based on the models, we figure out the impact of the mobility. The effectiveness validation of the developed models is also verified by simulations.
  Long-Hua Ma , Ming Xu , Meng Shao and Zhe-Ming Lu
  Randomness and parameter selection in the Particle Swarm Optimization (PSO) algorithm had great influence on its performance. This study presented a formal convergence and spectral radius analysis of the standard PSO algorithm model, where some of the parameters were stochastic. Based on the analysis of the relationship of {ω, c1, c2}, a sufficient condition was given to guarantee that the PSO algorithm was mean-square convergent, using the stochastic process theory. Then, the mean spectral radius was constructed. According to the relationship between the spectral radius and the convergent speed, it was shown that, a small spectral radius lead to a faster convergent speed than a big one. By optimizing the mean spectral radius of the PSO algorithm in the mean-square convergent region, a minimum spectral radius and corresponding parameter selection guidelines were derived to guarantee that the PSO algorithm was mean-square convergent and had a fast convergent speed in the stochastic sense. Finally, one parameter selection {c1 = c2 = 2, ω = 0.4222} was proposed. with the parameter, the study gave examples whose performance on benchmark functions were superior to previously published results.
  Chao-Yun Li , Yang-Chun Cao , Shi-Zhao Li , Ming Xu , Chan-Juan Liu , Zhi-Peng Yu , Xiang-Hui Zhao and Jun-Hu Yao
  This research was conducted to investigate the effects of exogenous fibrolytic enzyme on in vitro ruminal fermentation and microbial populations with substrates in different Forage to Concentrate ratios (F:C). Four levels (0, 40, 80 and 120 U g-1 dry matter substrate) of fibrolytic enzyme were supplemented to buffered rumen fluid and incubated with three different F:C ratios (80:20, 50:50 and 20:80) substrates at 39°C. After 24 h incubation, the results showed that in three different F:C ratios, fibrolytic enzyme significantly increased (p<0.001) total gas production, in vitro dry matter disappearance, concentration of total volatile fatty acid and molar proportion of propionate and decreased (p<0.001) pH but it did not significantly (p>0.05) affect molar proportion of butyrate. And in the high (F:C 80:20) and medium (F:C 50:50) forage substrates, fibrolytic enzyme increased (p<0.05) the molar proportion of propionate and decreased (p<0.05) the ratio of acetate to propionate but the effects did not observed in high concentrate (F:C 20:80) substrates. It was also found that fibrolytic enzyme increased (p<0.05) the number of Fibrobacter succinogenes and methanogens in the F:C 80:20 substrate but there was no significant (p>0.05) effects on microbial populations in the F:C 50:50 and 20:80 substrates. The results indicated that the fibrolytic enzyme improved the degradation of substrates and had different effects on the ruminal fermentation pattern and microbial populations under three F:C ratio substrates. The efficiency of fibrolytic enzyme on high and medium forage substrates was greater than low forage substrates.
  Guojin Chen , Miaofen Zhu , Jing Ni , Ming Xu and Huipeng Chen
  The two-cylinder drive is one of many commonly used mechanical drive forms. Its synchronous control accuracy determines the movement accuracy of the working machinery. The study established the mathematical model for the two-cylinder electro-hydraulic servo synchronous drive system and revealed that the two-cylinder horizontal electro-hydraulic synchronous drive system has the cascade form of the linear system with the nonlinear system. Taking the band sawing machine and the broaching machine as the application object, the paper analyzed their compositions and synchronization CNC systems. Aiming at the dual-cylinder drive form for the broaching machine, the IPSO-PID synchronous controller of the two-cylinder system was designed. Through the digital simulation and actual testing, the results show that the IPSO-PID synchronous controller is faster in the tracking response speed and better in the synchronization performance than the conventional PID synchronization controller.
  Kaizheng Gong , Zijian Li , Ming Xu , Jianhai Du , Zhizhen Lv and Youyi Zhang
  A growing body of evidence has demonstrated that p38 mitogen-activated protein kinase (MAPK) has a crucial role in various physiological and pathological processes mediated by β2-adrenergic receptors (β2-ARs). However, the detailed mechanism of β2-ARs-induced p38 MAPK activation has not yet been fully defined. The present study demonstrates a novel kinetic model of p38 MAPK activation induced by β2-ARs in human embryonic kidney 293A cells. The β2-AR agonist isoproterenol induced a time-dependent biphasic phosphorylation of p38 MAPK: the early phase peaked at 10 min, and was followed by a delayed phase that appeared at 90 min and was sustained for 6 h. Interestingly, inhibition of the cAMP/protein kinase A (PKA) pathway failed to affect the early phosphorylation but abolished the delayed activation. By contrast, silencing of β-arrestin-1 expression by small interfering RNA inhibited the early phase activation of p38 MAPK. Furthermore, the NADPH oxidase complex is a downstream target of β-arrestin-1, as evidenced by the fact that isoproterenol-induced Rac1 activation was also suppressed by β-arrestin-1 knockdown. In addition, early phase activation of p38 MAPK was prevented by inactivation of Rac1 and NADPH oxidase by pharmacological inhibitors, overexpression of a dominant negative mutant of Rac1, and p47phox knockdown by RNA interference. Of note, we demonstrated that only early activation of p38 MAPK is involved in isoproterenol-induced F-actin rearrangement. Collectively, these data suggest that the classic cAMP/PKA pathway is responsible for the delayed activation, whereas a β-arrestin-1/Rac1/NADPH oxidase-dependent signaling is a heretofore unrecognized mechanism for β2-AR-mediated early activation of p38 MAPK.
 
 
 
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