Through simulation of summer and winter precipitation cases in China, the cloud precipitation schemes of model were examined. Results indicate that it is discrepant between convective precipitation simulated by the Ka...Through simulation of summer and winter precipitation cases in China, the cloud precipitation schemes of model were examined. Results indicate that it is discrepant between convective precipitation simulated by the Kain-Fritsch （KF） scheme and Betts-Miller （BM） scheme in summer, the former scheme is better than the latter in this case. The ambient atmosphere may be varied by different convective schemes. The air is wetter and the updraft is stronger in the KF scheme than in the BM scheme, which can induce the more grid scale precipitation in the KF scheme, i.e., the different cumulus schemes may have the different and important effect on the grid scale precipitation. However, there is almost no convective rain in winter in northern China, so the effect of cumulus precipitation on the grid scale precipitation can be disregarded. Therefore, the gird scale precipitation is primary in the winter of northern China.展开更多
A 2-dimensional multicomponent ion transport model based on Nernst-Planck(NP)equation and electroneutrality assumption is developed for an electrodialysis(ED)cell operated in the ohmic regime.The flow in channels are ...A 2-dimensional multicomponent ion transport model based on Nernst-Planck(NP)equation and electroneutrality assumption is developed for an electrodialysis(ED)cell operated in the ohmic regime.The flow in channels are assumed incompressible,isothermal,and laminar.Donnan equilibrium and flux continuity are considered at ionexchange membrane(IEM)-solution interfaces.To account for tortuosity effects inside membranes,effective ionic diffusion coefficients are calculated using membranes water volume fractions.The developed multicomponent model is used to elucidate the effects of feed solution properties,cell properties,system hydrodynamics,operational conditions,and membrane properties on selective divalent ion removal in the cell.The results indicate that the selective removal of divalent ions improves with decreasing the cell length,imposed potential,and ionic strength of feed water.Enhanced mixing in spacer-filled cell also promotes selective divalent ion removal.Higher concentrations of fixed charges on the membranes results in greater selectivity toward divalent ions at short cell length and low imposed potentials.With equal concentrations of fixed charges,membranes with high water content are less favorable for selective divalent ion removal.The developed framework enables the optimum selection of cell design,IEMs,spacer design,and operational conditions to selectively remove ions from multicomponent solutions.展开更多
基金Supported by Foundation from the Institute of Tropical & Marine Meteorology in 2004the National Basic Research Program of China (2004CB418306).
文摘Through simulation of summer and winter precipitation cases in China, the cloud precipitation schemes of model were examined. Results indicate that it is discrepant between convective precipitation simulated by the Kain-Fritsch （KF） scheme and Betts-Miller （BM） scheme in summer, the former scheme is better than the latter in this case. The ambient atmosphere may be varied by different convective schemes. The air is wetter and the updraft is stronger in the KF scheme than in the BM scheme, which can induce the more grid scale precipitation in the KF scheme, i.e., the different cumulus schemes may have the different and important effect on the grid scale precipitation. However, there is almost no convective rain in winter in northern China, so the effect of cumulus precipitation on the grid scale precipitation can be disregarded. Therefore, the gird scale precipitation is primary in the winter of northern China.
基金the financial support of the Maddox Foundation and the Donovan Maddox Distinguished Engineering Chair Endowment.
文摘A 2-dimensional multicomponent ion transport model based on Nernst-Planck(NP)equation and electroneutrality assumption is developed for an electrodialysis(ED)cell operated in the ohmic regime.The flow in channels are assumed incompressible,isothermal,and laminar.Donnan equilibrium and flux continuity are considered at ionexchange membrane(IEM)-solution interfaces.To account for tortuosity effects inside membranes,effective ionic diffusion coefficients are calculated using membranes water volume fractions.The developed multicomponent model is used to elucidate the effects of feed solution properties,cell properties,system hydrodynamics,operational conditions,and membrane properties on selective divalent ion removal in the cell.The results indicate that the selective removal of divalent ions improves with decreasing the cell length,imposed potential,and ionic strength of feed water.Enhanced mixing in spacer-filled cell also promotes selective divalent ion removal.Higher concentrations of fixed charges on the membranes results in greater selectivity toward divalent ions at short cell length and low imposed potentials.With equal concentrations of fixed charges,membranes with high water content are less favorable for selective divalent ion removal.The developed framework enables the optimum selection of cell design,IEMs,spacer design,and operational conditions to selectively remove ions from multicomponent solutions.
