In this article,we consider linear transformation using minimum and maximum values of the auxiliary variable and obtain two new ratio estimators.The efficiency of different ratio estimation are compared and then we pr...In this article,we consider linear transformation using minimum and maximum values of the auxiliary variable and obtain two new ratio estimators.The efficiency of different ratio estimation are compared and then we present the rules of choosing efficient estimator in different situations.展开更多
In order to simulate the airflow in anhydrous case and the water-air flow in groundwater case, a numerical model of airflow in soil was developed. For the nonlinearity of the governing partial differential equation, t...In order to simulate the airflow in anhydrous case and the water-air flow in groundwater case, a numerical model of airflow in soil was developed. For the nonlinearity of the governing partial differential equation, the corresponding discretization and linearization methods were given. Due to the mass transfer between air-phase and water-phase, phase states of the model elements were constantly changing. Thus, parameters of the model were divided into primary ones and secondary ones, and the primary variables changing with phase states and the secondary variables can be obtained by their functional relationship with the primary variables. Additionally, the special definite condition of this numerical model was illustrated. Two examples were given to simulate the airflow in soil whether there was groundwater or not, and the effectiveness of the numerical model is verified by comparing the results of simulation with that of exoeriment.展开更多
文摘In this article,we consider linear transformation using minimum and maximum values of the auxiliary variable and obtain two new ratio estimators.The efficiency of different ratio estimation are compared and then we present the rules of choosing efficient estimator in different situations.
基金Project(Y5080022) supported by the Natural Science Foundation of Zhejiang Province,ChinaProject(RC1202) supported by Scientific and Technological Program of Water Resources Department of Zhejiang Province in 2012,ChinaProject(Y201224384) supported by Scientific Research Program of Education Department of Zhejiang Province in 2012,China
文摘In order to simulate the airflow in anhydrous case and the water-air flow in groundwater case, a numerical model of airflow in soil was developed. For the nonlinearity of the governing partial differential equation, the corresponding discretization and linearization methods were given. Due to the mass transfer between air-phase and water-phase, phase states of the model elements were constantly changing. Thus, parameters of the model were divided into primary ones and secondary ones, and the primary variables changing with phase states and the secondary variables can be obtained by their functional relationship with the primary variables. Additionally, the special definite condition of this numerical model was illustrated. Two examples were given to simulate the airflow in soil whether there was groundwater or not, and the effectiveness of the numerical model is verified by comparing the results of simulation with that of exoeriment.
