According to the structural characteristics of hazardous waste landfill and the leakage current model of high voltage DC Landfill leakage detection, a sealed model is established detail. The detection layer of the haz...According to the structural characteristics of hazardous waste landfill and the leakage current model of high voltage DC Landfill leakage detection, a sealed model is established detail. The detection layer of the hazardous waste landfill is considered as a sealed assumed that the source current flows through the leak entirely. The leak is regard and analyzed in space and it is ed as a positive current resource ＋ I located at the current entrance or a negative resource - I located at the current exit, which depends on the placement of the current supply. The electrical potential of an arbitrary in detection layer satisfies Poisson equation. The boundary condition is regarded as a natural bound- ary condition for the high resistivity of high density polyethylene （HDPE） membrane. Based on which a numerical calculation method is developed. Satisfactory agreement between experimental da- ta and simulated data validates the analysis. Parametric studies show that a larger horizontal distance between the power supply electrode and leak and a smaller distance between the detector electrodes and the detected liner are helpful to leak location. More parametric curves show that parameters leaks can be detected effectively with optimum selection of field survey.展开更多
According to the structural characteristics of hazardous waste landfill, a new model based on the finite element method （FEM） is developed. The detection layer is considered as a sealed space and it is assumed that ...According to the structural characteristics of hazardous waste landfill, a new model based on the finite element method （FEM） is developed. The detection layer is considered as a sealed space and it is assumed that total current flows through the leak for the high resistivity of geomembrane liner. The leak current is regarded as a positive point current ＋I and the other current source is -I. Electrical potential of an arbitrary point in detection layer satisfies Poisson equation. Experiments for detecting leaks in liner were carried out. Excellent agreement between experimental data and simulated model data validates the new model. Parametric curves for a single leak show that with optimum selection of field survey parameters leaks can be detected effectively. For multiple leaks, the simulated results indicate that they are detectable when leak separation is larger than measurement spacing.展开更多
A buried-oxide trench-gate bipolar-mode JFET （BTB-JFET） with an oxide layer buried under the gate region to reduce the gate-drain capacitance Cgd is proposed. Simulations with a resistive load circuit for power loss...A buried-oxide trench-gate bipolar-mode JFET （BTB-JFET） with an oxide layer buried under the gate region to reduce the gate-drain capacitance Cgd is proposed. Simulations with a resistive load circuit for power loss comparison at high frequency application are performed with 20V-rated power switching devices,including a BTB-JFET,a trench MOSFET （T-MOSFET） generally applied in present industry, and a conventional trench-gate bipolar-mode JFET （TB-JFET） without buried oxide,for the first time. The simulation results indicate that the switching power loss of the normally-on BTB-JFET is improved by 37% and 14% at 1MHz compared to the T-MOSFET and the normally-on TB-JFET, respectively. In order to demonstrate the validity of the simulation, the normally-on TB-JFET and BTB-JFET have been fabricated successfully for the first time, where the buried oxide structure is realized by thermal oxidation. The experimental results show that the Cgd of the BTB-JFET is decreased by 45% from that of the TB-JFET at zero source-drain bias. Compared to the TB-JFET,the switching time and switching power loss of the BTB-JFET decrease approximately by 7. 4% and 11% at 1MHz,respectively. Therefore,the normally-on BTB-JFET could be pointing to a new direction for the R＆D of low volt- age and high frequency switching devices.展开更多
基金Supported by the National Basic Research Development Program of China(No.2010CB428506)the National High Technology Research and Development Program(No.2007AA061303)Beijing Higher Education Young Elite Teacher Project(YETP1756)
文摘According to the structural characteristics of hazardous waste landfill and the leakage current model of high voltage DC Landfill leakage detection, a sealed model is established detail. The detection layer of the hazardous waste landfill is considered as a sealed assumed that the source current flows through the leak entirely. The leak is regard and analyzed in space and it is ed as a positive current resource ＋ I located at the current entrance or a negative resource - I located at the current exit, which depends on the placement of the current supply. The electrical potential of an arbitrary in detection layer satisfies Poisson equation. The boundary condition is regarded as a natural bound- ary condition for the high resistivity of high density polyethylene （HDPE） membrane. Based on which a numerical calculation method is developed. Satisfactory agreement between experimental da- ta and simulated data validates the analysis. Parametric studies show that a larger horizontal distance between the power supply electrode and leak and a smaller distance between the detector electrodes and the detected liner are helpful to leak location. More parametric curves show that parameters leaks can be detected effectively with optimum selection of field survey.
基金Project supported by the National High-Technology Research and Development Program of China(Grant No.2001AA644010)
文摘According to the structural characteristics of hazardous waste landfill, a new model based on the finite element method （FEM） is developed. The detection layer is considered as a sealed space and it is assumed that total current flows through the leak for the high resistivity of geomembrane liner. The leak current is regarded as a positive point current ＋I and the other current source is -I. Electrical potential of an arbitrary point in detection layer satisfies Poisson equation. Experiments for detecting leaks in liner were carried out. Excellent agreement between experimental data and simulated model data validates the new model. Parametric curves for a single leak show that with optimum selection of field survey parameters leaks can be detected effectively. For multiple leaks, the simulated results indicate that they are detectable when leak separation is larger than measurement spacing.
文摘A buried-oxide trench-gate bipolar-mode JFET （BTB-JFET） with an oxide layer buried under the gate region to reduce the gate-drain capacitance Cgd is proposed. Simulations with a resistive load circuit for power loss comparison at high frequency application are performed with 20V-rated power switching devices,including a BTB-JFET,a trench MOSFET （T-MOSFET） generally applied in present industry, and a conventional trench-gate bipolar-mode JFET （TB-JFET） without buried oxide,for the first time. The simulation results indicate that the switching power loss of the normally-on BTB-JFET is improved by 37% and 14% at 1MHz compared to the T-MOSFET and the normally-on TB-JFET, respectively. In order to demonstrate the validity of the simulation, the normally-on TB-JFET and BTB-JFET have been fabricated successfully for the first time, where the buried oxide structure is realized by thermal oxidation. The experimental results show that the Cgd of the BTB-JFET is decreased by 45% from that of the TB-JFET at zero source-drain bias. Compared to the TB-JFET,the switching time and switching power loss of the BTB-JFET decrease approximately by 7. 4% and 11% at 1MHz,respectively. Therefore,the normally-on BTB-JFET could be pointing to a new direction for the R＆D of low volt- age and high frequency switching devices.
