Simultaneous optimization and control for polypropylene grade transition with two-layer hierarchical structure

In this paper,a two-layer hierarchical structure of optimization and control for polypropylene grade transition was raised to overcome process uncertain disturbances that led to the large deviation between the open-loop reference trajectory and the actual process.In the upper layer,the variant time scale based control vector parametric methods(VTS-CVP) was used for dynamic optimization of transition reference trajectory,while nonlinear model predictive controller(NMPC) based on closed-loop subspace and piece-wise linear(SSARX-PWL) model in the lower layer was tracking to the reference trajectory from the upper layer for overcoming high-frequency disturbances.Besides,mechanism about trajectory deviation detection and optimal trajectory updating online were introduced to ensure a smooth transition for the entire process.The proposed method was validated with the real data from an industrial double-loop propylene polymerization reaction process with developed dynamic mechanism mathematical model.

Evaluation of regional water security using water poverty index

Water security is a widely concerned issue in the world nowadays.A new method,water poverty index(WPI),was applied to evaluate the regional water security.Twelve state farms in Heilongjiang Province,Northeastern China were selected to evaluate water security status based on the data of 2006 using WPI and mean deviation grading method.The method of WPI includes five key indices:resources(R),access(A),capacity(C),utilization(U)and environment(E).Each key index further consists of several sub-indices.According to the results of WPI,the grade of each farm was calculated by using the method of mean deviation grading.Thus,the radar images can be protracted of each farm.From the radar images,the conclusions can be drawn that the WPI values of Farm 853 and Hongqiling are under very safe status,while that of Farm Raohe is under safe status,those of Farms Youyi,597,852,291 and Jiangchuan are under moderate safe status,that of Farm Beixing is under low safe status and those of Farm Shuangyashan,Shuguang and Baoshan are under unsafe status.The results from this study can provide basic information for decision making on rational utilization of water resources and regulations for regional water safety guarantee system.