A mathematical model was developed to monitor the facilitated transport of germanium(IV) from oxalic acid solutions through a flat sheet supported liquid membrane(FSSLM) containing four trialkylphosphine oxides(Cyanex...A mathematical model was developed to monitor the facilitated transport of germanium(IV) from oxalic acid solutions through a flat sheet supported liquid membrane(FSSLM) containing four trialkylphosphine oxides(Cyanex 923). The FSSLM modeling was based on the extraction constant(Kext) calculated from the liquid-liquid extraction(LLX) modeling. The LLX model presented a reliable calculation of the extraction constant(Kex= 2.057×103 L/mol4). The FSSLM model was solved using Matlab■ software according to extraction constant, Fick’s law, and diffusional principles. The model predicts the overall mass transfer coefficient(Korg) to be 3.84 cm/s. Using this value, diffusion coefficients(Dm) for various Cyanex 923 concentrations of 0.126, 0.252, 0.378, 0.505, 0.631 and 0.757 mol/L are found to be 8.50×10^-4, 4.30×10^-4, 1.87×10^-4, 5.87×10^-5, 2.57×10^-5, 2.09×10^-5 cm2/s, respectively. The results show that the diffusion rate of the current study is approximately more than that of similar FSSLM systems containing Cyanex 923 used to transport various metals. The modeling values are in good agreement with the experimental data, showing the good reliability of the mathematical model.展开更多
A combined model of solute transport and water flow was developed to simulate the migration of methanol, a soluble organic chemical, in unsaturated soil zone. The solute transport equation considered convective-disper...A combined model of solute transport and water flow was developed to simulate the migration of methanol, a soluble organic chemical, in unsaturated soil zone. The solute transport equation considered convective-dispersive transport in the liquid phase as well as diffusion in the gas phase. The effect of rainfall and evapotranspiration on transport was considered at the boundary conditions of the governing equations. Data on the characteristics of a loam soil and the climatic conditions in southern California were also introduced to compare the results with those from a study in the USA in which the profiles of methanol distribution and water content in the soil zone at different times had been depicted. This comparison showed that there was good agreement between the two studies. The results showed that methanol contamination reached a depth of about 250 cm after 8 760 h. In contrast, if rainfall and evapotranspiration were not considered, the depth was only about 140 cm. The model therefore confirmed that rainfall strongly affected solute transport.展开更多
Ontology is the conceptual backbone that provides meaning to data on the semantic web. However, ontology is not a static resource and may evolve over time, which often leaves the meaning of data in an undefined or inc...Ontology is the conceptual backbone that provides meaning to data on the semantic web. However, ontology is not a static resource and may evolve over time, which often leaves the meaning of data in an undefined or inconsistent state. It is thus very important to have a method to preserve the data and its meaning when ontology changes. This paper proposed a general method that solves the problem using data migration. It analyzed some of the issues in the method including separation of ontology and data, migration specification, migration result and migration algorithm. The paper also instantiates the general mothod in RDF(S) as an example. The RDF(S) example itself is a simple but complete method for migrating RDF data when RDFS ontology changes.展开更多
文摘A mathematical model was developed to monitor the facilitated transport of germanium(IV) from oxalic acid solutions through a flat sheet supported liquid membrane(FSSLM) containing four trialkylphosphine oxides(Cyanex 923). The FSSLM modeling was based on the extraction constant(Kext) calculated from the liquid-liquid extraction(LLX) modeling. The LLX model presented a reliable calculation of the extraction constant(Kex= 2.057×103 L/mol4). The FSSLM model was solved using Matlab■ software according to extraction constant, Fick’s law, and diffusional principles. The model predicts the overall mass transfer coefficient(Korg) to be 3.84 cm/s. Using this value, diffusion coefficients(Dm) for various Cyanex 923 concentrations of 0.126, 0.252, 0.378, 0.505, 0.631 and 0.757 mol/L are found to be 8.50×10^-4, 4.30×10^-4, 1.87×10^-4, 5.87×10^-5, 2.57×10^-5, 2.09×10^-5 cm2/s, respectively. The results show that the diffusion rate of the current study is approximately more than that of similar FSSLM systems containing Cyanex 923 used to transport various metals. The modeling values are in good agreement with the experimental data, showing the good reliability of the mathematical model.
基金Project supported by the National Natural Science Foundation of China (No. 20276048).
文摘A combined model of solute transport and water flow was developed to simulate the migration of methanol, a soluble organic chemical, in unsaturated soil zone. The solute transport equation considered convective-dispersive transport in the liquid phase as well as diffusion in the gas phase. The effect of rainfall and evapotranspiration on transport was considered at the boundary conditions of the governing equations. Data on the characteristics of a loam soil and the climatic conditions in southern California were also introduced to compare the results with those from a study in the USA in which the profiles of methanol distribution and water content in the soil zone at different times had been depicted. This comparison showed that there was good agreement between the two studies. The results showed that methanol contamination reached a depth of about 250 cm after 8 760 h. In contrast, if rainfall and evapotranspiration were not considered, the depth was only about 140 cm. The model therefore confirmed that rainfall strongly affected solute transport.
文摘Ontology is the conceptual backbone that provides meaning to data on the semantic web. However, ontology is not a static resource and may evolve over time, which often leaves the meaning of data in an undefined or inconsistent state. It is thus very important to have a method to preserve the data and its meaning when ontology changes. This paper proposed a general method that solves the problem using data migration. It analyzed some of the issues in the method including separation of ontology and data, migration specification, migration result and migration algorithm. The paper also instantiates the general mothod in RDF(S) as an example. The RDF(S) example itself is a simple but complete method for migrating RDF data when RDFS ontology changes.
