The semi-quantum two-orbital exchange model is used to investigate the effect of small rare-earth ion substitution on orthorhombic RMnO 3 with A-type antiferromagnetic order,using the Monte Carlo algorithm,exact diago...The semi-quantum two-orbital exchange model is used to investigate the effect of small rare-earth ion substitution on orthorhombic RMnO 3 with A-type antiferromagnetic order,using the Monte Carlo algorithm,exact diagonalization,and zero-temperature optimization approaches.It is revealed that the substitution results in a rich multiferroic phase diagram where the coexisting A-type antiferromagnetic phase and spiral spin phase,pure spiral spin phase,coexisting spiral spin phase,the E-type antiferromagnetic phase,and the pure E-type antiferromagnetic phase emerge in sequence.The multiferroic phase transitions modulate substantially the electric polarization,which is consistent qualitatively with recent experiments.展开更多
Researchers are paying more and more attention to the adsorption and transport of heavy metals in soil. In this study, laboratory experiments were performed to investigate the characteristics of adsorption and transpo...Researchers are paying more and more attention to the adsorption and transport of heavy metals in soil. In this study, laboratory experiments were performed to investigate the characteristics of adsorption and transport of mercury in soils of different locations in the western suburb of Beijing. To characterize the adsorption mechanism of mercury in soil, adsorption isotherms were determined through a batch experiment. Soil column experiments were performed in saturated soil under steady-state flow at a specific water head. The breakthrough curves (BTC) for the tracer (bromine) and mercury were obtained after continuous input. Moreover, two solute transport models [convection-dispersion equation model (CDE) and two-site non-equilibrium model (TSN)] were used to simulate heavy metal movement in soil on a laboratory column scale. According to the simulating results, we explored which model is more adapted to simulate the movement of heavy metals in saturated soil in the western suburb of Beijing.展开更多
This study investigated the effects of pH on the transport of Pb 2＋ , Mn 2＋ , Zn 2＋ and Ni 2＋ through lateritic soil columns. Model results by fitting the symmetric breakthrough curves （BTCs） of bromide （Br ） ...This study investigated the effects of pH on the transport of Pb 2＋ , Mn 2＋ , Zn 2＋ and Ni 2＋ through lateritic soil columns. Model results by fitting the symmetric breakthrough curves （BTCs） of bromide （Br ） with CXTFIT model suggested that physical non-equilibrium processes were absent in the columns. The heavy metal BTCs were, however, asymmetrical and exhibited a tailing phenomenon, indicating the presence of chemical non-equilibrium processes in the columns. The retardation factors of Pb 2＋ were the largest of the four metal ions at both pH 4.0 （33.3） and pH 5.0 （35.4）. The use of Langmuir isotherm parameters from batch studies with HYDRUS-1D did not predict the BTCs well. Rather the two-site model （TSM） described the heavy metal BTCs better than the equilibrium linear/nonlinear Langmuir model. The fraction of instantaneous sorption sites （ f ） of all four metal ions on the lateritic soil was consistently about 30%–44% of the total sorption sites.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 51031004,11004027,and 11074113)the National Basic Research Program of China (Grant Nos. 2011CB922101 and 2009CB929501)the Priority Academic Program Development of Jiangsu Provincial Higher Education Institutions,China
文摘The semi-quantum two-orbital exchange model is used to investigate the effect of small rare-earth ion substitution on orthorhombic RMnO 3 with A-type antiferromagnetic order,using the Monte Carlo algorithm,exact diagonalization,and zero-temperature optimization approaches.It is revealed that the substitution results in a rich multiferroic phase diagram where the coexisting A-type antiferromagnetic phase and spiral spin phase,pure spiral spin phase,coexisting spiral spin phase,the E-type antiferromagnetic phase,and the pure E-type antiferromagnetic phase emerge in sequence.The multiferroic phase transitions modulate substantially the electric polarization,which is consistent qualitatively with recent experiments.
基金This study is granted by the Foundation for the Social Service of Minis-try of Science and Technology (2001DIA10021). And also is granted byChina Ministry of Science and Technology under the program of"Ecologi-cal and Environmental Monitoring, Forcasting and Management System inMining Area"(No. 2004DIB3J110) and"Development and Experimentof Ecological and Environmental Monitoring and Forcasting Technology forMining Area"(No. 2005BA901A03).
文摘Researchers are paying more and more attention to the adsorption and transport of heavy metals in soil. In this study, laboratory experiments were performed to investigate the characteristics of adsorption and transport of mercury in soils of different locations in the western suburb of Beijing. To characterize the adsorption mechanism of mercury in soil, adsorption isotherms were determined through a batch experiment. Soil column experiments were performed in saturated soil under steady-state flow at a specific water head. The breakthrough curves (BTC) for the tracer (bromine) and mercury were obtained after continuous input. Moreover, two solute transport models [convection-dispersion equation model (CDE) and two-site non-equilibrium model (TSN)] were used to simulate heavy metal movement in soil on a laboratory column scale. According to the simulating results, we explored which model is more adapted to simulate the movement of heavy metals in saturated soil in the western suburb of Beijing.
基金the National Center of Excellence for Environmental and Hazardous Waste Management(NCE-EHWM)the Geology Department of Chulalongkorn University
文摘This study investigated the effects of pH on the transport of Pb 2＋ , Mn 2＋ , Zn 2＋ and Ni 2＋ through lateritic soil columns. Model results by fitting the symmetric breakthrough curves （BTCs） of bromide （Br ） with CXTFIT model suggested that physical non-equilibrium processes were absent in the columns. The heavy metal BTCs were, however, asymmetrical and exhibited a tailing phenomenon, indicating the presence of chemical non-equilibrium processes in the columns. The retardation factors of Pb 2＋ were the largest of the four metal ions at both pH 4.0 （33.3） and pH 5.0 （35.4）. The use of Langmuir isotherm parameters from batch studies with HYDRUS-1D did not predict the BTCs well. Rather the two-site model （TSM） described the heavy metal BTCs better than the equilibrium linear/nonlinear Langmuir model. The fraction of instantaneous sorption sites （ f ） of all four metal ions on the lateritic soil was consistently about 30%–44% of the total sorption sites.
