Suffusion in broadly graded granular soils is caused by fluid flow and is a typical cause of geo-hazards.Previous studies of it have mainly focused on suffusion in homogeneous soil specimens.In this study,the coupled ...Suffusion in broadly graded granular soils is caused by fluid flow and is a typical cause of geo-hazards.Previous studies of it have mainly focused on suffusion in homogeneous soil specimens.In this study,the coupled discrete element method(DEM)and computational fluid dynamics(CFD)approach is adopted to model suffusion in multi-layered soils with different fines contents,and soils with one or more impermeable zones.The parameters of the CFD-DEM model are first calibrated with the classic Ergun test and a good match with experiment is obtained.Then suffusion in multi-layered soils with different fines contents and impermeable zones is simulated and discussed.The simulation results show that,for soils with multiple layers,the cumulative eroded mass is mainly determined by the fines content of the bottom layer.In general,the higher the fines content of the bottom soil layer,the higher the cumulative eroded mass.In addition,suffusion is more severe if the fines content of the layer above is decreased.Impermeable zones inside soil specimens can increase the flow velocity around those zones,facilitating the migration of fine particles and intensifying suffusion.展开更多
The experiment was set up for examining the physiological and biological indexes quickly and exactly, for obtaining information of tobacco-field fertilizing and tobacco growing. The ASD Field spec FR 2500 was used to ...The experiment was set up for examining the physiological and biological indexes quickly and exactly, for obtaining information of tobacco-field fertilizing and tobacco growing. The ASD Field spec FR 2500 was used to measure spectra reflectance of flue-cured tobacco and the relationship between hyperspectral parameters and biochemical contents （total nitrogen, chlorophyll, carotenoid）, and physiological indexes （fresh weight, dry weight, moisture content） of flue-cured tobacco leaves was studied by correlation and stepwise regression statistic methods at different nitrogen and potassium levels. The results indicated that the spectra curves of different treatments had obvious rules and great diversities. There were high correlations between different types of spectra parameters and ten physiological and biochemical indexes of flue-cured tobacco leaves. Hyperspectral characteristic variables of ten physiological and biochemical indexes were found through stepwise regression, and SDr/SDb was the characteristic variable closest to seven biochemical contents. Simultaneously, the R2 and regression coefficient of equations reached 0.05 significant level and the equations had good estimating effects through the examination of other samples. Accordingly, this study suggested that the ten physiological and biochemical indexes could be estimated quickly by the estimating models, at the same time nitrogen-potassium fertilization and growth condition of flue-cured tobacco could be inspected.展开更多
Singlet fission(SF)has potential applications in high-efficiency photo-energy harvesting applications,but its practical application is hindered by the limited number of materials.In this work,we explored the bay aroma...Singlet fission(SF)has potential applications in high-efficiency photo-energy harvesting applications,but its practical application is hindered by the limited number of materials.In this work,we explored the bay aromatic substitution strategy for the design of new perylenediimide(PDI)based SF materials.A series of PDI derivatives with biphenyl or naphthalene units substituted at the bay posi-tions were designed and synthesized to investigate the effects of aromatic substitutes on their photodynamic behaviours.The bay substitutions do not shift the energy level of the PDI core significantly but give rise to different intermolecular coupling strengths in the thin films and affect the intermolecular SF efficiency.Femtosecond transient absorption(fsTA)spectroscopy reveals that appro-priate spacing configuration from the bay aromatic substitution groups enhances the SF yields by promoting the interaction of neighbouring PDI cores.Triplet exciton yields of up to 183%have been obtained from these new PDI derivatives,making them po-tential candidates in future SF-based optoelectronics.展开更多
基金This work is supported by the Research Grants Council(RGC)of Hong Kong(No.15226322)the National Natu‐ral Science Foundation of China(No.42207210).
文摘Suffusion in broadly graded granular soils is caused by fluid flow and is a typical cause of geo-hazards.Previous studies of it have mainly focused on suffusion in homogeneous soil specimens.In this study,the coupled discrete element method(DEM)and computational fluid dynamics(CFD)approach is adopted to model suffusion in multi-layered soils with different fines contents,and soils with one or more impermeable zones.The parameters of the CFD-DEM model are first calibrated with the classic Ergun test and a good match with experiment is obtained.Then suffusion in multi-layered soils with different fines contents and impermeable zones is simulated and discussed.The simulation results show that,for soils with multiple layers,the cumulative eroded mass is mainly determined by the fines content of the bottom layer.In general,the higher the fines content of the bottom soil layer,the higher the cumulative eroded mass.In addition,suffusion is more severe if the fines content of the layer above is decreased.Impermeable zones inside soil specimens can increase the flow velocity around those zones,facilitating the migration of fine particles and intensifying suffusion.
文摘The experiment was set up for examining the physiological and biological indexes quickly and exactly, for obtaining information of tobacco-field fertilizing and tobacco growing. The ASD Field spec FR 2500 was used to measure spectra reflectance of flue-cured tobacco and the relationship between hyperspectral parameters and biochemical contents （total nitrogen, chlorophyll, carotenoid）, and physiological indexes （fresh weight, dry weight, moisture content） of flue-cured tobacco leaves was studied by correlation and stepwise regression statistic methods at different nitrogen and potassium levels. The results indicated that the spectra curves of different treatments had obvious rules and great diversities. There were high correlations between different types of spectra parameters and ten physiological and biochemical indexes of flue-cured tobacco leaves. Hyperspectral characteristic variables of ten physiological and biochemical indexes were found through stepwise regression, and SDr/SDb was the characteristic variable closest to seven biochemical contents. Simultaneously, the R2 and regression coefficient of equations reached 0.05 significant level and the equations had good estimating effects through the examination of other samples. Accordingly, this study suggested that the ten physiological and biochemical indexes could be estimated quickly by the estimating models, at the same time nitrogen-potassium fertilization and growth condition of flue-cured tobacco could be inspected.
基金supported by the National Natural Science Foundation of China(NSFC 51733004,51525303,21702085,21602093,21572086,22075117,92256202,U22A20399)the Fundamental Research Funds for the Central Universities(lzujbky-2022-kb01,Izujbky-2021-sp33,Izujbky-2021-27),and Supercomputing Center of Lanzhou University.
文摘Singlet fission(SF)has potential applications in high-efficiency photo-energy harvesting applications,but its practical application is hindered by the limited number of materials.In this work,we explored the bay aromatic substitution strategy for the design of new perylenediimide(PDI)based SF materials.A series of PDI derivatives with biphenyl or naphthalene units substituted at the bay posi-tions were designed and synthesized to investigate the effects of aromatic substitutes on their photodynamic behaviours.The bay substitutions do not shift the energy level of the PDI core significantly but give rise to different intermolecular coupling strengths in the thin films and affect the intermolecular SF efficiency.Femtosecond transient absorption(fsTA)spectroscopy reveals that appro-priate spacing configuration from the bay aromatic substitution groups enhances the SF yields by promoting the interaction of neighbouring PDI cores.Triplet exciton yields of up to 183%have been obtained from these new PDI derivatives,making them po-tential candidates in future SF-based optoelectronics.
