For the solid-solid transformation from formⅡto formⅠof isotactic polybutene-1(iPB),the temperature dependence of formⅠnucleation and growth was deemed to control the transformation process.However,the relationship...For the solid-solid transformation from formⅡto formⅠof isotactic polybutene-1(iPB),the temperature dependence of formⅠnucleation and growth was deemed to control the transformation process.However,the relationship between formⅠformation and formⅡdisappearance in the transformation process is not clear.In this work,the spontaneous crystal transformation from formⅡtoⅠof iPB with 81 mol%mmmm sequence concentration is studied firstly by tracking the two processes,the decay of formⅡand the yielding of formⅠin a wide range of temperature spanning from 0℃to 50℃and in a long transformation time ranging from 5 min to 65 days with in situ FTIR and WAXD.Unlike the literature reports,the decay rate of formⅡis firstly found to be lower than the yielding rate of formⅠat all studied temperatures,especially at low transition temperature.This is attributed to the amorphous chains which locate near crystal lamella participating into the nucleation of formⅡ.The regular chain folding and growth of i PB formⅠfrom amorphous chains containing short isotactic sequences also lead to an increase in crystallinity of formⅠcompared with that of initial formⅡcrystallized at 60℃.An increase in the annealing temperature results in decrease in crystallinity and increase in lamellae thickness of i PB formⅠ.展开更多
Solvent annealing is a facile method for changing the aggregated microstructure and physical properties of polymer materials.In this paper,we addressed the effects of solvent vapor annealing,including chloroform and w...Solvent annealing is a facile method for changing the aggregated microstructure and physical properties of polymer materials.In this paper,we addressed the effects of solvent vapor annealing,including chloroform and water vapor,on the polymorphic transformation in both hot-pressed film and electrospun nonwoven of isotactic polybutene-1(PB-1)by means of in situ Fourier transform infrared spectroscopy(FTIR).The pretty rapid transition rate caused by the increased motion of molecular chains under chloroform vapor is associated with a lowest crystallinity.Also,a decreased crystallinity with the crystal transition occurred in electrospun nonwovens resulting from the relaxation of the stretched molecular chains into amorphous state rather than realignment into crystal form I predominating the crystal transition process.展开更多
The grey wolf （Canis lupus） is one of the most widely distributed terrestrial mammals, and its distribution and ecology in Europe and North America are largely well described. However, the distribution of grey wolve...The grey wolf （Canis lupus） is one of the most widely distributed terrestrial mammals, and its distribution and ecology in Europe and North America are largely well described. However, the distribution of grey wolves in southern China is still highly controversial. Several well-known western literatures stated that there were no grey wolves in southern China, while the presence of grey wolves across China has been indicated in A Guide to the Mammals of China, published by Princeton University Press. It is essential to solve this discrepancy since dogs may have originated from grey wolves in southern China. Therefore, we systematically investigated Chinese literatures about wild animal surveys and identified more than 100 articles and books that included information of the distribution of grey wolves in China. We also surveyed the collections of three Chinese natural museums and found 26 grey wolf skins specimens collected across China. Moreover, we investigated the fossil records in China and identified 25 archaeological sites with wolf remains including south China. In conclusion, with the comprehensive summary of Chinese literatures, museum specimens and fossil records, we demonstrate that grey wolves do distribute across all parts of the Chinese mainland, including the most southern parts.展开更多
The composition and structure of polymer largely determine the properties of its final products.As a novel polymer material,the composition,structure,and properties of the isotactic polypropylene/polybutene-1 in-react...The composition and structure of polymer largely determine the properties of its final products.As a novel polymer material,the composition,structure,and properties of the isotactic polypropylene/polybutene-1 in-reactor alloy(PPIPB alloy)synthesized by sequential two-stage polymerization with Ziegler-Natta catalyst were correlated for the first time in this work.The iPP/PB alloy was fractionated by temperature rising elution fractionation(TREF)in a broad temperature ranged from-30℃to 140℃,and the chain microstructures and sequence distributions of isolated fractions were analyzed by DSC,GPC,13C-NMR,and FTIR.The iPP/IPB alloy was composed of five components,namely high isotactic PB(PB,85.8 wt96),medium isotactic PB(mPB,5.1 wt%),polyl(butene-1)-block propylene copolymers(PB-6 PP,4.1 wt%6)which contained PB and PP blocks with dfferent lengths according to the isolation temperature,isotactic PP(iPP,2.7 wt%6),and atactic PB(aPB,2.3 wt96).Compared to other commercial pipe materials,the P/iPB alloy presented outstanding thermal creep resistance and gas permeability resistance,high strength and low deformation at high temperature,and appropriate flexural strength.The roles of PP and PB-b-PP components in the alloy were interpreted.This work is expected to elucidate the potential application of PPIPB aloy as pipe materials and provide solutions for the design and synthesis of high performance pipe materials.展开更多
The catalytic activity and stereospecificity of olefin polymerization by using heterogeneous TiCl_(4)/MgCl_(2)Ziegler-Natta(Z-N)catalysts are determined by the structure and nature of active centers,which are mysterio...The catalytic activity and stereospecificity of olefin polymerization by using heterogeneous TiCl_(4)/MgCl_(2)Ziegler-Natta(Z-N)catalysts are determined by the structure and nature of active centers,which are mysterious and fairly controversial.In this work,the propylene polymerization kinetics under different polymerization temperatures by using Z-N catalysts were investigated through monitoring the concentration of active centers[C*]with different tacticity.SEM was applied to characterize the catalyst morphologies and growing polypropylene(PP)particles.The lamellar thickness and crystallizability of PP obtained under different polymerization conditions were analyzed by DSC and SAXS.The PP fractions and active centers with different tacticity were obtained with solvent extraction fractionation method.The catalytic activity,active centers with different tacticity and propagation rate constant kp,fragmentation of the catalyst,crystalline structure of PP are correlated with temperature and time for propylene polymerizations.The polymerization temperature and time show complex influences on the propylene polymerization.The higher polymerization temperature(60℃)resulted higher activity,kp and lower[C*],and the isotactic active centers Ci*as the majority ones producing the highest isotactic polypropylene(iPP)components showed much higher kp when compared with the active centers with lower stereoselectivity.Appropriate polymerization time provided full fragmentation of the catalyst and minimum diffusion limitation.This work aims to elucidate the formation and evolution of active centers with different tacticity under different polymerization temperature and time and its relations with the fragmentation of the PP/catalyst particles,and provide the solutions to the improvement of catalyst activity and isotacticity of PP.展开更多
Pedestrian evacuation is actually a process of behavioral evolution. Interaction behaviors between pedestrians affect not only the evolution of their cooperation strategy, but also their evacuation paths-scheduling an...Pedestrian evacuation is actually a process of behavioral evolution. Interaction behaviors between pedestrians affect not only the evolution of their cooperation strategy, but also their evacuation paths-scheduling and dynamics features. The existence of interaction behaviors and cooperation evolution is therefore critical for pedestrian evacuation. To address this issue, an extended cellular automaton(CA) evacuation model considering the effects of interaction behaviors and cooperation evolution is proposed here. The influence mechanism of the environment factor and interaction behaviors between neighbors on the decision-making of one pedestrian to path scheduling is focused. Average payoffs interacting with neighbors are used to represent the competitive ability of one pedestrian, aiming to solve the conflicts when more than one pedestrian competes for the same position based on a new method. Influences of interaction behaviors, the panic degree and the conflict cost on the evacuation dynamics and cooperation evolution of pedestrians are discussed. Simulation results of the room evacuation show that the interaction behaviors between pedestrians to a certain extent are beneficial to the evacuation efficiency and the formation of cooperation behaviors as well. The increase of conflict cost prolongs the evacuation time. Panic emotions of pedestrians are bad for cooperation behaviors of the crowd and have complex effects on evacuation time. A new self-organization effect is also presented.展开更多
基金financially supported by the Major Science and Technology Innovation Project of Shandong Province(No.2019JZZY010352)Natural Science Foundation of Shandong Province(ZR2019MB072)Taishan Scholar Program
文摘For the solid-solid transformation from formⅡto formⅠof isotactic polybutene-1(iPB),the temperature dependence of formⅠnucleation and growth was deemed to control the transformation process.However,the relationship between formⅠformation and formⅡdisappearance in the transformation process is not clear.In this work,the spontaneous crystal transformation from formⅡtoⅠof iPB with 81 mol%mmmm sequence concentration is studied firstly by tracking the two processes,the decay of formⅡand the yielding of formⅠin a wide range of temperature spanning from 0℃to 50℃and in a long transformation time ranging from 5 min to 65 days with in situ FTIR and WAXD.Unlike the literature reports,the decay rate of formⅡis firstly found to be lower than the yielding rate of formⅠat all studied temperatures,especially at low transition temperature.This is attributed to the amorphous chains which locate near crystal lamella participating into the nucleation of formⅡ.The regular chain folding and growth of i PB formⅠfrom amorphous chains containing short isotactic sequences also lead to an increase in crystallinity of formⅠcompared with that of initial formⅡcrystallized at 60℃.An increase in the annealing temperature results in decrease in crystallinity and increase in lamellae thickness of i PB formⅠ.
基金financially supported by the Special Foundation of Taishan Mountain Scholar Constructive Programthe National Natural Science Foundation of China(No.21174074)+3 种基金Shandong Provincical Key R&D Program(No.2015GGX102019)Shandong Provincial Natural Science Fund for Distinguished Young Scholars(No.JQ201213)the Nature Science Foundation of Shandong Province(No.ZR2013BM004)the Yellow River Delta Scholar program(Office of National University Science&Technology Park Administrative Committee(China University of Petroleum))
文摘Solvent annealing is a facile method for changing the aggregated microstructure and physical properties of polymer materials.In this paper,we addressed the effects of solvent vapor annealing,including chloroform and water vapor,on the polymorphic transformation in both hot-pressed film and electrospun nonwoven of isotactic polybutene-1(PB-1)by means of in situ Fourier transform infrared spectroscopy(FTIR).The pretty rapid transition rate caused by the increased motion of molecular chains under chloroform vapor is associated with a lowest crystallinity.Also,a decreased crystallinity with the crystal transition occurred in electrospun nonwovens resulting from the relaxation of the stretched molecular chains into amorphous state rather than realignment into crystal form I predominating the crystal transition process.
基金supported by grants from the National Natural Science Foundation of China(91531303)the 973 program(2013CB835200 and 2013CB835202)+3 种基金the Breakthrough Project of Strategic Priority Program of the Chinese Academy of Sciences(XDB13000000)grants from the Carl Trygger Foundationthe Agria and Swedish Kennel Club research foundationsupported by the Youth Innovation Promotion Association,Chinese Academy of Sciences
文摘The grey wolf （Canis lupus） is one of the most widely distributed terrestrial mammals, and its distribution and ecology in Europe and North America are largely well described. However, the distribution of grey wolves in southern China is still highly controversial. Several well-known western literatures stated that there were no grey wolves in southern China, while the presence of grey wolves across China has been indicated in A Guide to the Mammals of China, published by Princeton University Press. It is essential to solve this discrepancy since dogs may have originated from grey wolves in southern China. Therefore, we systematically investigated Chinese literatures about wild animal surveys and identified more than 100 articles and books that included information of the distribution of grey wolves in China. We also surveyed the collections of three Chinese natural museums and found 26 grey wolf skins specimens collected across China. Moreover, we investigated the fossil records in China and identified 25 archaeological sites with wolf remains including south China. In conclusion, with the comprehensive summary of Chinese literatures, museum specimens and fossil records, we demonstrate that grey wolves do distribute across all parts of the Chinese mainland, including the most southern parts.
基金supported by the Major Scientific and Technological Innovation Project of Shandong Province(No.2019JZZY010352)Natural Science Foundation of Shandong Province(No.ZR2019MB072)and Taishan Scholar Program.
文摘The composition and structure of polymer largely determine the properties of its final products.As a novel polymer material,the composition,structure,and properties of the isotactic polypropylene/polybutene-1 in-reactor alloy(PPIPB alloy)synthesized by sequential two-stage polymerization with Ziegler-Natta catalyst were correlated for the first time in this work.The iPP/PB alloy was fractionated by temperature rising elution fractionation(TREF)in a broad temperature ranged from-30℃to 140℃,and the chain microstructures and sequence distributions of isolated fractions were analyzed by DSC,GPC,13C-NMR,and FTIR.The iPP/IPB alloy was composed of five components,namely high isotactic PB(PB,85.8 wt96),medium isotactic PB(mPB,5.1 wt%),polyl(butene-1)-block propylene copolymers(PB-6 PP,4.1 wt%6)which contained PB and PP blocks with dfferent lengths according to the isolation temperature,isotactic PP(iPP,2.7 wt%6),and atactic PB(aPB,2.3 wt96).Compared to other commercial pipe materials,the P/iPB alloy presented outstanding thermal creep resistance and gas permeability resistance,high strength and low deformation at high temperature,and appropriate flexural strength.The roles of PP and PB-b-PP components in the alloy were interpreted.This work is expected to elucidate the potential application of PPIPB aloy as pipe materials and provide solutions for the design and synthesis of high performance pipe materials.
基金financially supported by the Major Scientific and Technological Innovation Project of Shandong Province(No.2019JZZY010352)Natural Science Foundation of Shandong Province(No.ZR2019MB072)Taishan Scholar Program。
文摘The catalytic activity and stereospecificity of olefin polymerization by using heterogeneous TiCl_(4)/MgCl_(2)Ziegler-Natta(Z-N)catalysts are determined by the structure and nature of active centers,which are mysterious and fairly controversial.In this work,the propylene polymerization kinetics under different polymerization temperatures by using Z-N catalysts were investigated through monitoring the concentration of active centers[C*]with different tacticity.SEM was applied to characterize the catalyst morphologies and growing polypropylene(PP)particles.The lamellar thickness and crystallizability of PP obtained under different polymerization conditions were analyzed by DSC and SAXS.The PP fractions and active centers with different tacticity were obtained with solvent extraction fractionation method.The catalytic activity,active centers with different tacticity and propagation rate constant kp,fragmentation of the catalyst,crystalline structure of PP are correlated with temperature and time for propylene polymerizations.The polymerization temperature and time show complex influences on the propylene polymerization.The higher polymerization temperature(60℃)resulted higher activity,kp and lower[C*],and the isotactic active centers Ci*as the majority ones producing the highest isotactic polypropylene(iPP)components showed much higher kp when compared with the active centers with lower stereoselectivity.Appropriate polymerization time provided full fragmentation of the catalyst and minimum diffusion limitation.This work aims to elucidate the formation and evolution of active centers with different tacticity under different polymerization temperature and time and its relations with the fragmentation of the PP/catalyst particles,and provide the solutions to the improvement of catalyst activity and isotacticity of PP.
基金Project supported by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(Grant No.2017YFC083300)the National Natural Science Foundation of China(Grant Nos.91646201,U1633203,and 51808422)the Independent Innovation Foundation of Wuhan University and Technology,China(Grant No.2019IVA011)。
文摘Pedestrian evacuation is actually a process of behavioral evolution. Interaction behaviors between pedestrians affect not only the evolution of their cooperation strategy, but also their evacuation paths-scheduling and dynamics features. The existence of interaction behaviors and cooperation evolution is therefore critical for pedestrian evacuation. To address this issue, an extended cellular automaton(CA) evacuation model considering the effects of interaction behaviors and cooperation evolution is proposed here. The influence mechanism of the environment factor and interaction behaviors between neighbors on the decision-making of one pedestrian to path scheduling is focused. Average payoffs interacting with neighbors are used to represent the competitive ability of one pedestrian, aiming to solve the conflicts when more than one pedestrian competes for the same position based on a new method. Influences of interaction behaviors, the panic degree and the conflict cost on the evacuation dynamics and cooperation evolution of pedestrians are discussed. Simulation results of the room evacuation show that the interaction behaviors between pedestrians to a certain extent are beneficial to the evacuation efficiency and the formation of cooperation behaviors as well. The increase of conflict cost prolongs the evacuation time. Panic emotions of pedestrians are bad for cooperation behaviors of the crowd and have complex effects on evacuation time. A new self-organization effect is also presented.
