In this paper we address the dynamics of compensation cutting process from both Laplace s frequency domain and the time domain of the first time, using the two computer aided analyzing softwares: MATLAB and SIMULI...In this paper we address the dynamics of compensation cutting process from both Laplace s frequency domain and the time domain of the first time, using the two computer aided analyzing softwares: MATLAB and SIMULINK. Theoretical analysis and simulation experiments firstly show that not only the systematical stiffness of workpiece, spindle and tools, but also the regenerated coefficient affects the compensation displacement effect. The results show that the SREC is practicable in reality to decease the spindle induced errors in many engineering applications such as hard boring through simulation and the preliminary experiment results.展开更多
Some sufficient conditions are obtained for the oscillation of first order neutral differential_difference equations with positive and negative periodic coefficients.
When the machine tool is in the start-and stop-stages,the stick-slip phenomenon will be observed and highprecision positioning,machining accuracy and fretting feed will not be guaranteed. The most critical reason is t...When the machine tool is in the start-and stop-stages,the stick-slip phenomenon will be observed and highprecision positioning,machining accuracy and fretting feed will not be guaranteed. The most critical reason is that there is the difference between the dynamic and the static friction coefficients. Textures with different area ratios are fabricated on the surfaces of the upper PTFE-based composite and the friction tests are carried out on a reciprocating tribotester under the boundary lubrication and flat-on-flat contact conditions. The results show that there exists an optimal textured area ratio of 19.6% that can minimize the difference between the dynamic and the static friction coefficients.展开更多
This paper reviews the historic understanding of the predictability of atmospheric and oceanic motions, and interprets it in a general framework. On this basis, the existing challenges and unsolved problems in the stu...This paper reviews the historic understanding of the predictability of atmospheric and oceanic motions, and interprets it in a general framework. On this basis, the existing challenges and unsolved problems in the study of the intrinsic predictability limit(IPL) of weather and climate events of different spatio-temporal scales are summarized. Emphasis is also placed on the structure of the initial error and model parameter errors as well as the associated targeting observation issue. Finally, the predictability of atmospheric and oceanic motion in the ensemble-probabilistic methods widely used in current operational forecasts are discussed.The necessity of considering IPLs in the framework of stochastic dynamic systems is also addressed.展开更多
Based on 1,3-propanediol production from batch fermentation of glycerol by Klebsiella pneurnoniae, a multistage dynamic system and its parameter identification are discussed in this paper. The batch fermentation proce...Based on 1,3-propanediol production from batch fermentation of glycerol by Klebsiella pneurnoniae, a multistage dynamic system and its parameter identification are discussed in this paper. The batch fermentation process is divided into three stages exhibiting different dynamic behaviors and characteristics, from which a corresponding nonlinear multistage dynamic system is built. We then propose a parameter identification optimization model whose objective function is the average relative error. The model is solved by particle swarm optimization weighted by inertia, and the result shows that the relative error of our proposed model is 2-10%smaller than those of existing models.展开更多
文摘In this paper we address the dynamics of compensation cutting process from both Laplace s frequency domain and the time domain of the first time, using the two computer aided analyzing softwares: MATLAB and SIMULINK. Theoretical analysis and simulation experiments firstly show that not only the systematical stiffness of workpiece, spindle and tools, but also the regenerated coefficient affects the compensation displacement effect. The results show that the SREC is practicable in reality to decease the spindle induced errors in many engineering applications such as hard boring through simulation and the preliminary experiment results.
文摘Some sufficient conditions are obtained for the oscillation of first order neutral differential_difference equations with positive and negative periodic coefficients.
基金financially supported by the National Natural Science Foundation of China (No. 51675268)
文摘When the machine tool is in the start-and stop-stages,the stick-slip phenomenon will be observed and highprecision positioning,machining accuracy and fretting feed will not be guaranteed. The most critical reason is that there is the difference between the dynamic and the static friction coefficients. Textures with different area ratios are fabricated on the surfaces of the upper PTFE-based composite and the friction tests are carried out on a reciprocating tribotester under the boundary lubrication and flat-on-flat contact conditions. The results show that there exists an optimal textured area ratio of 19.6% that can minimize the difference between the dynamic and the static friction coefficients.
基金supported by the National Natural Science Foundation of China(Grant Nos.41230420,41376018&41606012)
文摘This paper reviews the historic understanding of the predictability of atmospheric and oceanic motions, and interprets it in a general framework. On this basis, the existing challenges and unsolved problems in the study of the intrinsic predictability limit(IPL) of weather and climate events of different spatio-temporal scales are summarized. Emphasis is also placed on the structure of the initial error and model parameter errors as well as the associated targeting observation issue. Finally, the predictability of atmospheric and oceanic motion in the ensemble-probabilistic methods widely used in current operational forecasts are discussed.The necessity of considering IPLs in the framework of stochastic dynamic systems is also addressed.
基金Acknowledgments This work was supported by the National Natural Science Foundation of China （Grant No. 10871033）, ＂863＂ Program （No. 2007AA02Z208） and ＂973＂ Program （No. 2007CB71430c）.
文摘Based on 1,3-propanediol production from batch fermentation of glycerol by Klebsiella pneurnoniae, a multistage dynamic system and its parameter identification are discussed in this paper. The batch fermentation process is divided into three stages exhibiting different dynamic behaviors and characteristics, from which a corresponding nonlinear multistage dynamic system is built. We then propose a parameter identification optimization model whose objective function is the average relative error. The model is solved by particle swarm optimization weighted by inertia, and the result shows that the relative error of our proposed model is 2-10%smaller than those of existing models.
