Three-dimensionally ordered macroporous polystyrene(3DOM PS) with pore size of 350 nm was fabricated using Cp2Co/Ethyl 2-bromoisobutyrate(EBiB) catalytic system by ATRP.The resulting polymers were detected by FT-IR,1H...Three-dimensionally ordered macroporous polystyrene(3DOM PS) with pore size of 350 nm was fabricated using Cp2Co/Ethyl 2-bromoisobutyrate(EBiB) catalytic system by ATRP.The resulting polymers were detected by FT-IR,1H-NMR,SEM,and GPC.The microstructure of 3DOM PS was confirmed by FT-IR and 1H-NMR.SEM micrographs show that both silica spheres within the templates and pores in the 3DOM polystyrene are arranged in highly ordered fashion,and the shrinkage of the pores in the 3DOM PS is 24%.GPC curves show that the 3DOM PS possesses slightly lower Mn and narrow MWD compared with bulk one.This result indicats that living polymerization is different from non-living polymerizationin in the confined space.展开更多
The A-site ordered perovskite oxides with chemical formula AA＇3B4O（12）display many intriguing physical properties due to the introduction of transition metals at both A and B sites. Here, research on the recently d...The A-site ordered perovskite oxides with chemical formula AA＇3B4O（12）display many intriguing physical properties due to the introduction of transition metals at both A and B sites. Here, research on the recently discovered intermetallic charge transfer occurring between A-site Cu and B-site Fe ions in La Cu3Fe4O（12） and its analogues is reviewed, along with work on the magnetoelectric multiferroicity observed in La Mn3Cr4O（12） with cubic perovskite structure. The Cu–Fe intermetallic charge transfer（LaCu3（3＋）Fe4（3＋）O（12）→ LaCu3（2＋）Fe4（3.75＋）O（12）） leads to a first-order isostructural phase transition accompanied by drastic variations in magnetism and electrical transport properties. The La Mn3Cr4O（12） is a novel spindriven multiferroic system with strong magnetoelectric coupling effects. The compound is the first example of cubic perovskite multiferroics to be found. It opens up a new arena for studying unexpected multiferroic mechanisms.展开更多
The efficient dynamic modeling and vibration transfer analysis of a fluid-delivering branch pipeline(FDBP)are essential for analyzing vibration coupling effects and implementing vibration reduction optimization.Theref...The efficient dynamic modeling and vibration transfer analysis of a fluid-delivering branch pipeline(FDBP)are essential for analyzing vibration coupling effects and implementing vibration reduction optimization.Therefore,this study proposes a reduced-order dynamic modeling method suitable for FDBPs and then analyzes the vibration transfer characteristics.For the modeling method,the finite element method and absorbing transfer matrix method(ATMM)are integrated,considering the fluid–structure coupling effect and fluid disturbances.The dual-domain dynamic substructure method is developed to perform the reduced-order modeling of FDBP,and ATMM is adopted to reduce the matrix order when solving fluid disturbances.Furthermore,the modeling method is validated by experiments on an H-shaped branch pipeline.Finally,transient and steady-state vibration transfer analyses of FDBP are performed,and the effects of branch locations on natural characteristics and vibration transfer behavior are analyzed.Results show that transient vibration transfer represents the transfer and conversion of the kinematic,strain,and damping energies,while steady-state vibration transfer characteristics are related to the vibration mode.In addition,multiple-order mode exchanges are triggered when branch locations vary in frequency-shift regions,and the mode-exchange regions are also the transformation ones for vibration transfer patterns.展开更多
An improved Reduced-Order Model(ROM)is proposed based on a flow-solution preprocessing operation and a fast sampling strategy to efficiently and accurately predict ionized hypersonic flows.This ROM is generated in low...An improved Reduced-Order Model(ROM)is proposed based on a flow-solution preprocessing operation and a fast sampling strategy to efficiently and accurately predict ionized hypersonic flows.This ROM is generated in low-dimensional space by performing the Proper Orthogonal Decomposition(POD)on snapshots and is coupled with the Radial Basis Function(RBF)to achieve fast prediction speed.However,due to the disparate scales in the ionized flow field,the conventional ROM usually generates spurious negative errors.Here,this issue is addressed by performing flow-solution preprocessing in logarithmic space to improve the conventional ROM.Then,extra orthogonal polynomials are introduced in the RBF interpolation to achieve additional improvement of the prediction accuracy.In addition,to construct high-efficiency snapshots,a trajectory-constrained adaptive sampling strategy based on convex hull optimization is developed.To evaluate the performance of the proposed fast prediction method,two hypersonic vehicles with classic configurations,i.e.a wave-rider and a reentry capsule,are used to validate the proposed method.Both two cases show that the proposed fast prediction method has high accuracy near the vehicle surface and the free-stream region where the flow field is smooth.Compared with the conventional ROM prediction,the prediction results are significantly improved by the proposed method around the discontinuities,e.g.the shock wave and the ionized layer.As a result,the proposed fast prediction method reduces the error of the conventional ROM by at least 45%,with a speedup of approximately 2.0×105compared to the Computational Fluid Dynamic(CFD)simulations.These test cases demonstrate that the method developed here is efficient and accurate for predicting ionized hypersonic flows.展开更多
基金Supported by National Natural Science Foundation of China (Grant No. 50273009)Natural Science Foundation of Hebei Province (Grant No. E2007000052)+1 种基金Science Research Plan of Department of Education,Hebei Province (Grant No. 2007307)Doctor Open Foundation of Key Laboratory of Functional Polymer Material of Ministry of Education,Nankai University) (Grant No. 2006-007)
文摘Three-dimensionally ordered macroporous polystyrene(3DOM PS) with pore size of 350 nm was fabricated using Cp2Co/Ethyl 2-bromoisobutyrate(EBiB) catalytic system by ATRP.The resulting polymers were detected by FT-IR,1H-NMR,SEM,and GPC.The microstructure of 3DOM PS was confirmed by FT-IR and 1H-NMR.SEM micrographs show that both silica spheres within the templates and pores in the 3DOM polystyrene are arranged in highly ordered fashion,and the shrinkage of the pores in the 3DOM PS is 24%.GPC curves show that the 3DOM PS possesses slightly lower Mn and narrow MWD compared with bulk one.This result indicats that living polymerization is different from non-living polymerizationin in the confined space.
基金Project supported by the National Basic Research Program of China(Grant No.2014CB921500)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB07030300)the National Natural Science Foundation of China(Grant No.11574378)
文摘The A-site ordered perovskite oxides with chemical formula AA＇3B4O（12）display many intriguing physical properties due to the introduction of transition metals at both A and B sites. Here, research on the recently discovered intermetallic charge transfer occurring between A-site Cu and B-site Fe ions in La Cu3Fe4O（12） and its analogues is reviewed, along with work on the magnetoelectric multiferroicity observed in La Mn3Cr4O（12） with cubic perovskite structure. The Cu–Fe intermetallic charge transfer（LaCu3（3＋）Fe4（3＋）O（12）→ LaCu3（2＋）Fe4（3.75＋）O（12）） leads to a first-order isostructural phase transition accompanied by drastic variations in magnetism and electrical transport properties. The La Mn3Cr4O（12） is a novel spindriven multiferroic system with strong magnetoelectric coupling effects. The compound is the first example of cubic perovskite multiferroics to be found. It opens up a new arena for studying unexpected multiferroic mechanisms.
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.N2403006)the National Science and Technology Major Project,China(Grant No.J2019-I-0008-0008).
文摘The efficient dynamic modeling and vibration transfer analysis of a fluid-delivering branch pipeline(FDBP)are essential for analyzing vibration coupling effects and implementing vibration reduction optimization.Therefore,this study proposes a reduced-order dynamic modeling method suitable for FDBPs and then analyzes the vibration transfer characteristics.For the modeling method,the finite element method and absorbing transfer matrix method(ATMM)are integrated,considering the fluid–structure coupling effect and fluid disturbances.The dual-domain dynamic substructure method is developed to perform the reduced-order modeling of FDBP,and ATMM is adopted to reduce the matrix order when solving fluid disturbances.Furthermore,the modeling method is validated by experiments on an H-shaped branch pipeline.Finally,transient and steady-state vibration transfer analyses of FDBP are performed,and the effects of branch locations on natural characteristics and vibration transfer behavior are analyzed.Results show that transient vibration transfer represents the transfer and conversion of the kinematic,strain,and damping energies,while steady-state vibration transfer characteristics are related to the vibration mode.In addition,multiple-order mode exchanges are triggered when branch locations vary in frequency-shift regions,and the mode-exchange regions are also the transformation ones for vibration transfer patterns.
基金supported by the National Natural Science Foundation of China(Nos.11902271 and 91952203)the Fundamental Research Funds for the Central Universities of China(No.G2019KY05102)111 project on“Aircraft Complex Flows and the Control”of China(No.B17037)。
文摘An improved Reduced-Order Model(ROM)is proposed based on a flow-solution preprocessing operation and a fast sampling strategy to efficiently and accurately predict ionized hypersonic flows.This ROM is generated in low-dimensional space by performing the Proper Orthogonal Decomposition(POD)on snapshots and is coupled with the Radial Basis Function(RBF)to achieve fast prediction speed.However,due to the disparate scales in the ionized flow field,the conventional ROM usually generates spurious negative errors.Here,this issue is addressed by performing flow-solution preprocessing in logarithmic space to improve the conventional ROM.Then,extra orthogonal polynomials are introduced in the RBF interpolation to achieve additional improvement of the prediction accuracy.In addition,to construct high-efficiency snapshots,a trajectory-constrained adaptive sampling strategy based on convex hull optimization is developed.To evaluate the performance of the proposed fast prediction method,two hypersonic vehicles with classic configurations,i.e.a wave-rider and a reentry capsule,are used to validate the proposed method.Both two cases show that the proposed fast prediction method has high accuracy near the vehicle surface and the free-stream region where the flow field is smooth.Compared with the conventional ROM prediction,the prediction results are significantly improved by the proposed method around the discontinuities,e.g.the shock wave and the ionized layer.As a result,the proposed fast prediction method reduces the error of the conventional ROM by at least 45%,with a speedup of approximately 2.0×105compared to the Computational Fluid Dynamic(CFD)simulations.These test cases demonstrate that the method developed here is efficient and accurate for predicting ionized hypersonic flows.
