Ethylene-propylene copolymers were synthesized using a TiCl4/MgCl2/SiO2/diester type supported Ziegler-Natta catalyst with or without the presence of hydrogen in a slurry polymerization process.The copolymer was inhom...Ethylene-propylene copolymers were synthesized using a TiCl4/MgCl2/SiO2/diester type supported Ziegler-Natta catalyst with or without the presence of hydrogen in a slurry polymerization process.The copolymer was inhomogeneous in composition and can be fractionated into two parts, fractions soluble and insoluble in n-octane at room temperature, respectively.The soluble part is a nearly random copolymer,while the insoluble part is a kind of segmented copolymer,as revealed by 13 C-NMR and DSC analyses.Adding H2 in the reaction system caused an increase of copolymer yield and a decrease of the insoluble part,but the propylene content and average length of propylene segments of the insoluble part were markedly increased,meanwhile the average length of ethylene segments of the insoluble part was markedly decreased.Copolymer sequence distribution of the soluble part was only slightly changed by H2. The segmented copolymer fraction present in this ethylene-propylene copolymer has the similar structure as the segmented copolymer fractions found in polypropylene/poly（ethylene-co-propylene） reactor alloy.Mechanism of the hydrogen effect on copolymer structure is discussed.展开更多
20250301基于模糊PID的玉米精播电控排种系统//DOI:10.25165/j.ijabe.20241704.8247针对传统播种机地轮打滑导致玉米播种均匀性差的问题,该研究设计了一套玉米单粒精播电控排种系统,并确定了电机控制数学模型。通过Z-N法和模糊控制完成P...20250301基于模糊PID的玉米精播电控排种系统//DOI:10.25165/j.ijabe.20241704.8247针对传统播种机地轮打滑导致玉米播种均匀性差的问题,该研究设计了一套玉米单粒精播电控排种系统,并确定了电机控制数学模型。通过Z-N法和模糊控制完成P I D参数整定,借助MATLAB完成模糊PID控制的设计和Simulink仿真,将系统响应时间缩短了0.23 s,提高了控制精度。通过JPS-12排种器试验台试验,加装电控排种系统的排种器排种合格指数提高了4.47%,重播指数降低了1.96%,漏播指数降了2.81%,合格粒距变异系数降低了5.06%,排种均匀性得到了大幅度提高。展开更多
文摘Ethylene-propylene copolymers were synthesized using a TiCl4/MgCl2/SiO2/diester type supported Ziegler-Natta catalyst with or without the presence of hydrogen in a slurry polymerization process.The copolymer was inhomogeneous in composition and can be fractionated into two parts, fractions soluble and insoluble in n-octane at room temperature, respectively.The soluble part is a nearly random copolymer,while the insoluble part is a kind of segmented copolymer,as revealed by 13 C-NMR and DSC analyses.Adding H2 in the reaction system caused an increase of copolymer yield and a decrease of the insoluble part,but the propylene content and average length of propylene segments of the insoluble part were markedly increased,meanwhile the average length of ethylene segments of the insoluble part was markedly decreased.Copolymer sequence distribution of the soluble part was only slightly changed by H2. The segmented copolymer fraction present in this ethylene-propylene copolymer has the similar structure as the segmented copolymer fractions found in polypropylene/poly（ethylene-co-propylene） reactor alloy.Mechanism of the hydrogen effect on copolymer structure is discussed.
文摘20250301基于模糊PID的玉米精播电控排种系统//DOI:10.25165/j.ijabe.20241704.8247针对传统播种机地轮打滑导致玉米播种均匀性差的问题,该研究设计了一套玉米单粒精播电控排种系统,并确定了电机控制数学模型。通过Z-N法和模糊控制完成P I D参数整定,借助MATLAB完成模糊PID控制的设计和Simulink仿真,将系统响应时间缩短了0.23 s,提高了控制精度。通过JPS-12排种器试验台试验,加装电控排种系统的排种器排种合格指数提高了4.47%,重播指数降低了1.96%,漏播指数降了2.81%,合格粒距变异系数降低了5.06%,排种均匀性得到了大幅度提高。
