In this study, the developments in modeling gas-phase catalyzed olefin polymerization fluidized-bed reactors （FBR） using Ziegler-Natta catalyst is presented. The modified mathematical model to account for mass and h...In this study, the developments in modeling gas-phase catalyzed olefin polymerization fluidized-bed reactors （FBR） using Ziegler-Natta catalyst is presented. The modified mathematical model to account for mass and heat transfer between the solid particles and the surrounding gas in the emulsion phase is developed in this work to include site activation reaction. This model developed in the present study is subsequently compared with well-known models, namely, the bubble-growth, well-mixed and the constant bubble size models for porous and non porous catalyst. The results we obtained from the model was very close to the constant bubble size model, well-mixed model and bubble growth model at the beginning of the reaction but its overall behavior changed and is closer to the well-mixed model compared with the bubble growth model and constant bubble size model after half an hour of operation. Neural-network based predictive controller are implemented to control the system and compared with the conventional PID controller, giving acceptable results.展开更多
The existence of linear quadratic optimal control of ship automatic steering instruments is studied. Firstly, the sufficient conditions for the quadratic integrability of the solutions of linear second order time-vari...The existence of linear quadratic optimal control of ship automatic steering instruments is studied. Firstly, the sufficient conditions for the quadratic integrability of the solutions of linear second order time-variant differential equations are developed. Secondly, the optimal control form of the ship automatic steering instrument is obtained by using the dynamic programming method, which guarantees a minimal ship sway range, during long-distance navigation, by using as little energy as possible. Finally, based on the above mentioned sufficient conditions, the conditions for the realization of optimal control are obtained, which provides a foundation for choosing the weighted coefficients for optimal control in engineering.展开更多
Interaction of Aristolochic acid （AA） and guanine （G） was studied by electrochemical techniques in this paper. When AA was added into the guanine solution, the oxidation peak currents of mixture solution decreased...Interaction of Aristolochic acid （AA） and guanine （G） was studied by electrochemical techniques in this paper. When AA was added into the guanine solution, the oxidation peak currents of mixture solution decreased, while the peak potential and the electrochemical kinetic parameters remained the same as when AA was absent, except that the electrode process of guanine that involved two protons and two electrons changed from adsorption controlled to diffusion controlled. It is suggested that an electrochemical inactive supramolecular adduct AA-Gua （1：1） was formed in the system. The adduct cannot be oxidized on the glassy carbon electrode, which indirectly results in the decrease of the free concentration of guanine in the reaction solution and the decrease of peak currents. The binding constant （13） of this adduct is calculated as 7.14× 10^3 mol/L. The possible mechanism for the interaction of Aristolochic acid and DNA was proposed, that may provide a possible pathway for the nosogenesis research of aristolochic acid.展开更多
Existing works have addressed the interference mitigation by any two of the three approaches: link scheduling, power control, and successive interference cancellation(SIC). In this paper, we integrate the above approa...Existing works have addressed the interference mitigation by any two of the three approaches: link scheduling, power control, and successive interference cancellation(SIC). In this paper, we integrate the above approaches to further improve the spectral efficiency of the wireless networks and consider the max-min fairness to guarantee the transmission demand of the worst-case link. We formulate the link scheduling with joint power control and SIC(PCSIC) problem as a mixed-integer non-linear programming(MINLP), which has been proven to be NP-complete. Consequently, we propose an iterative algorithm to tackle the problem by decomposing it into a series of linear subproblems, and then the analysis shows that the algorithm has high complexity in the worst case. In order to reduce the computational complexity, we have further devised a two-stage algorithm with polynomial-time complexity. Numerical results show the performance improvements of our proposed algorithms in terms of the network throughput and power consumption compared with the link scheduling scheme only with SIC.展开更多
The paper presents a simplified numerical model of evaporation processes inside vertical tubes.In this model only the temperature fields in the fluid domain(the liquid or two-phase mixture) and solid domain(a tube wal...The paper presents a simplified numerical model of evaporation processes inside vertical tubes.In this model only the temperature fields in the fluid domain(the liquid or two-phase mixture) and solid domain(a tube wall) are determined.Therefore its performance and efficiency is high.The analytical formulas,which allow calculating the pressure drop and the distribution of heat transfer coefficient along the tube length,are used in this model.The energy equation for the fluid domain is solved with the Control Volume Method and for the solid domain with the Finite Element Method in order to determine the temperature field for the fluid and solid domains.展开更多
文摘In this study, the developments in modeling gas-phase catalyzed olefin polymerization fluidized-bed reactors （FBR） using Ziegler-Natta catalyst is presented. The modified mathematical model to account for mass and heat transfer between the solid particles and the surrounding gas in the emulsion phase is developed in this work to include site activation reaction. This model developed in the present study is subsequently compared with well-known models, namely, the bubble-growth, well-mixed and the constant bubble size models for porous and non porous catalyst. The results we obtained from the model was very close to the constant bubble size model, well-mixed model and bubble growth model at the beginning of the reaction but its overall behavior changed and is closer to the well-mixed model compared with the bubble growth model and constant bubble size model after half an hour of operation. Neural-network based predictive controller are implemented to control the system and compared with the conventional PID controller, giving acceptable results.
基金supported by National Nature Science Foundation of P.R.China(No.69974032).
文摘The existence of linear quadratic optimal control of ship automatic steering instruments is studied. Firstly, the sufficient conditions for the quadratic integrability of the solutions of linear second order time-variant differential equations are developed. Secondly, the optimal control form of the ship automatic steering instrument is obtained by using the dynamic programming method, which guarantees a minimal ship sway range, during long-distance navigation, by using as little energy as possible. Finally, based on the above mentioned sufficient conditions, the conditions for the realization of optimal control are obtained, which provides a foundation for choosing the weighted coefficients for optimal control in engineering.
基金Acknowledgements： Financial support from the National Natural Science Foundation of China （No. 20305004）, Program for New Century Excellent Talents in University （No, NCET-05-0572） of China, the Key Science and Technology project of Fujian Province （No. 2005Y015） and the National Natural Science Foundation of Fujian Province （No. D0510006）.
文摘Interaction of Aristolochic acid （AA） and guanine （G） was studied by electrochemical techniques in this paper. When AA was added into the guanine solution, the oxidation peak currents of mixture solution decreased, while the peak potential and the electrochemical kinetic parameters remained the same as when AA was absent, except that the electrode process of guanine that involved two protons and two electrons changed from adsorption controlled to diffusion controlled. It is suggested that an electrochemical inactive supramolecular adduct AA-Gua （1：1） was formed in the system. The adduct cannot be oxidized on the glassy carbon electrode, which indirectly results in the decrease of the free concentration of guanine in the reaction solution and the decrease of peak currents. The binding constant （13） of this adduct is calculated as 7.14× 10^3 mol/L. The possible mechanism for the interaction of Aristolochic acid and DNA was proposed, that may provide a possible pathway for the nosogenesis research of aristolochic acid.
基金supported by National Natural Science Foundation of China(Grant Nos.61231008,61172079,61201141,61301176,91338114)Science and Technology on Information Transmission and Dissemination in Communication Networks Laboratory Fund Project+1 种基金Programme of Introducing Talents of Discipline to Universities(Grant No.B08038)National High Technology Research and Development Program of China(Grant No.2014AA01A701)
文摘Existing works have addressed the interference mitigation by any two of the three approaches: link scheduling, power control, and successive interference cancellation(SIC). In this paper, we integrate the above approaches to further improve the spectral efficiency of the wireless networks and consider the max-min fairness to guarantee the transmission demand of the worst-case link. We formulate the link scheduling with joint power control and SIC(PCSIC) problem as a mixed-integer non-linear programming(MINLP), which has been proven to be NP-complete. Consequently, we propose an iterative algorithm to tackle the problem by decomposing it into a series of linear subproblems, and then the analysis shows that the algorithm has high complexity in the worst case. In order to reduce the computational complexity, we have further devised a two-stage algorithm with polynomial-time complexity. Numerical results show the performance improvements of our proposed algorithms in terms of the network throughput and power consumption compared with the link scheduling scheme only with SIC.
文摘The paper presents a simplified numerical model of evaporation processes inside vertical tubes.In this model only the temperature fields in the fluid domain(the liquid or two-phase mixture) and solid domain(a tube wall) are determined.Therefore its performance and efficiency is high.The analytical formulas,which allow calculating the pressure drop and the distribution of heat transfer coefficient along the tube length,are used in this model.The energy equation for the fluid domain is solved with the Control Volume Method and for the solid domain with the Finite Element Method in order to determine the temperature field for the fluid and solid domains.
