The crystal structure of tetrakis[(pyrrol-1-yl)methyl]methane was determined by X-ray diffraction measurement, and the result shows that it belongs to monoclinic crystal system, space group is P2 1/n, with a=0.9284(3...The crystal structure of tetrakis[(pyrrol-1-yl)methyl]methane was determined by X-ray diffraction measurement, and the result shows that it belongs to monoclinic crystal system, space group is P2 1/n, with a=0.9284(3) nm, b=1.0950(6) nm, c=1.8749(8) nm; α=γ= 90.00(4)°, β=103.63(3)°, V=1.8523(14) nm 3, Z=4, ρ calcd. =1.192 kg/m 3, μ=0.072 nm -1 , F(000)=712, R 1=0.0854, wR 2=0.1884. It has been found that the molecules exist in two enantiomeric states. Enantioselective self-assemblies such as one-dimensional molecular stacks in a single handedness, homochiral monolayers and a chiral superlattice are specified in this racemic crystal. In addition, a simple technique is advocated to distinguish chiral states from tetrahedral molecules in the solid state. The present R/S nomenclature of the tetracooradinated carbon centers is used solely for its convenience to distinguish the two enantiomeric states, but not used to determine the absolute configurations.展开更多
The efficiency and precision of parameter calibration in discrete element method （DEM） are not satisfactory, and parameter calibration for granular heat transfer is rarely involved. Accordingly, parameter calibratio...The efficiency and precision of parameter calibration in discrete element method （DEM） are not satisfactory, and parameter calibration for granular heat transfer is rarely involved. Accordingly, parameter calibration for granular heat transfer with the DEM is studied. The heat transfer in granular assemblies is simulated with DEM, and the effective thermal conductivity （ETC） of these granular assemblies is measured with the transient method in simulations. The measurement testbed is designed to test the ETC of the granular assemblies under normal pressure and a vacuum based on the steady method. Central composite design （CCD） is used to simulate the impact of the DEM parameters on the ETC of granular assemblies, and the heat transfer parameters are calibrated and compared with experimental data. The results show that, within the scope of the considered parameters, the ETC of the granular assemblies increases with an increasing particle thermal conductivity and decreases with an increasing particle shear modulus and particle diameter. The particle thermal conductivity has the greatest impact on the ETC of granular assemblies followed by the particle shear modulus and then the particle diameter. The calibration results show good agreement with the experimental results. The error is less than 4%, which is within a reasonable range for the scope of the CCD parameters. The proposed research provides high efficiency and high accuracy parameter calibration for granular heat transfer in DEM.展开更多
基金the National Natural Science Foundation of China(No.6 0 1710 0 8) and Shanghai Science and TechnologyCom mittee(No.0 2 14 nm0 0 5 )
文摘The crystal structure of tetrakis[(pyrrol-1-yl)methyl]methane was determined by X-ray diffraction measurement, and the result shows that it belongs to monoclinic crystal system, space group is P2 1/n, with a=0.9284(3) nm, b=1.0950(6) nm, c=1.8749(8) nm; α=γ= 90.00(4)°, β=103.63(3)°, V=1.8523(14) nm 3, Z=4, ρ calcd. =1.192 kg/m 3, μ=0.072 nm -1 , F(000)=712, R 1=0.0854, wR 2=0.1884. It has been found that the molecules exist in two enantiomeric states. Enantioselective self-assemblies such as one-dimensional molecular stacks in a single handedness, homochiral monolayers and a chiral superlattice are specified in this racemic crystal. In addition, a simple technique is advocated to distinguish chiral states from tetrahedral molecules in the solid state. The present R/S nomenclature of the tetracooradinated carbon centers is used solely for its convenience to distinguish the two enantiomeric states, but not used to determine the absolute configurations.
基金Supported by National Natural Science Foundation of China(Grant Nos.51105092,61403106)International Science and Technology Cooperation Program of China(Grant No.2014DFR50250)the 111 Project,China(Grant No.B07018)
文摘The efficiency and precision of parameter calibration in discrete element method （DEM） are not satisfactory, and parameter calibration for granular heat transfer is rarely involved. Accordingly, parameter calibration for granular heat transfer with the DEM is studied. The heat transfer in granular assemblies is simulated with DEM, and the effective thermal conductivity （ETC） of these granular assemblies is measured with the transient method in simulations. The measurement testbed is designed to test the ETC of the granular assemblies under normal pressure and a vacuum based on the steady method. Central composite design （CCD） is used to simulate the impact of the DEM parameters on the ETC of granular assemblies, and the heat transfer parameters are calibrated and compared with experimental data. The results show that, within the scope of the considered parameters, the ETC of the granular assemblies increases with an increasing particle thermal conductivity and decreases with an increasing particle shear modulus and particle diameter. The particle thermal conductivity has the greatest impact on the ETC of granular assemblies followed by the particle shear modulus and then the particle diameter. The calibration results show good agreement with the experimental results. The error is less than 4%, which is within a reasonable range for the scope of the CCD parameters. The proposed research provides high efficiency and high accuracy parameter calibration for granular heat transfer in DEM.
