The concepts of substrate eddy influence factor and distribution-effects-occurring frequency are presented. The effects of substrate resistivity and inductor spiral length on the substrate eddy and distribution effect...The concepts of substrate eddy influence factor and distribution-effects-occurring frequency are presented. The effects of substrate resistivity and inductor spiral length on the substrate eddy and distribution effects are captured. The substrate eddy influence factors of an inductor （6 turn, 3 060 μm in length） fabricated on low （ 1 Ω. cm） and high resistivity（ 1 000 Ω.cm） silicon substrates are 0. 3 and 0. 04, and the distribution-effects- occurring frequencies are 1.8 GHz and 14. 5 GHz, respectively. The measurement results show that the equivalent circuit model of the inductor on low resistivity silicon must take into consideration substrate eddy effects and distribution effects. However, the circuit model of the inductor on high resistivity silicon cannot take into account the substrate eddy effects and the distribution effects at the frequencies of interest. Its simple model shows agreement with the measurements, and the contrast is within 7%.展开更多
The influences of the mask wall angle on the current density distribution,shape of the evolving cavity and machining accuracy were investigated in electrochemical machining(ECM) by mask.A mathematical model was develo...The influences of the mask wall angle on the current density distribution,shape of the evolving cavity and machining accuracy were investigated in electrochemical machining(ECM) by mask.A mathematical model was developed to predict the shape evolution during the ECM by mask.The current density distribution is sensitive to mask wall angle.The evolution of cavity is determined by the current density distribution of evolving workpiece surface.The maximum depth is away from the center of holes machined,which leads to the island appearing at the center of cavity for mask wall angles greater than or equal to 90°(β≥90°).The experimental system was established and the simulation results were experimentally verified.The results indicate that the simulation results of cavity shape are consistent with the actual ones.The experiments also show that the repetition accuracy of matrix-hole for β≥90° is higher than that for β<90°.A hole taper is diminished,and the machining accuracy is improved with the mask wall angle increasing.展开更多
This article aims to investigate the transient behavior of a planar direct internal reforming solid oxide fuel cell （DIR-SOFC） comprehensively. A one-dimensional dynamic model of a planar D1R-SOFC is first developed...This article aims to investigate the transient behavior of a planar direct internal reforming solid oxide fuel cell （DIR-SOFC） comprehensively. A one-dimensional dynamic model of a planar D1R-SOFC is first developed based on mass and energy balances, and electrochemical principles. Further, a solution strategy is presented to solve the model, and the International Energy Agency （IEA） benchmark test is used to validate the model. Then, through model-based simulations, the steady-state performance of a co-flow planar DIR-SOFC under specified initial operating conditions and its dynamic response to introduced operating parameter disturbances are studied. The dynamic responses of important SOFC variables, such as cell temperature, current density, and cell voltage are all investigated when the SOFC is subjected to the step-changes in various operating parameters including both the load current and the inlet fuel and air flow rates. The results indicate that the rapid dynamics of the current density and the cell voltage are mainly influenced by the gas composition, particularly the H2 molar fraction in anode gas channels, while their slow dynamics are both dominated by the SOLID （including the PEN and interconnects） temperature. As the load current increases, the SOLID temperature and the maximum SOLID temperature gradient both increase, and thereby, the cell breakdown is apt to occur because of excessive thermal stresses. Changing the inlet fuel flow rate might lead to the change in the anode gas composition and the consequent change in the current density distribution and cell voltage. The inlet air flow rate has a great impact on the cell temperature distribution along the cell, and thus, is a suitable manipulated variable to control the cell temperature.展开更多
A plane-symmetric inhomogeneous cosmological model of perfect fluid distribution with electro-magnetic field is obtained. F12 is the non-vanishing component of electromagnetic field tensor. To get a deterministic solu...A plane-symmetric inhomogeneous cosmological model of perfect fluid distribution with electro-magnetic field is obtained. F12 is the non-vanishing component of electromagnetic field tensor. To get a deterministic solution, we assume the free gravitational field is Petrov type-Ⅱ non-degenerate. Some physical and geometric properties of the model are also discussed.展开更多
基金The National Natural Science Foundation of China(No.60676043)the National High Technology Research and Development Program of China(863Program)(No.2007AA04Z328)
文摘The concepts of substrate eddy influence factor and distribution-effects-occurring frequency are presented. The effects of substrate resistivity and inductor spiral length on the substrate eddy and distribution effects are captured. The substrate eddy influence factors of an inductor （6 turn, 3 060 μm in length） fabricated on low （ 1 Ω. cm） and high resistivity（ 1 000 Ω.cm） silicon substrates are 0. 3 and 0. 04, and the distribution-effects- occurring frequencies are 1.8 GHz and 14. 5 GHz, respectively. The measurement results show that the equivalent circuit model of the inductor on low resistivity silicon must take into consideration substrate eddy effects and distribution effects. However, the circuit model of the inductor on high resistivity silicon cannot take into account the substrate eddy effects and the distribution effects at the frequencies of interest. Its simple model shows agreement with the measurements, and the contrast is within 7%.
基金Project(50635040) supported by the National Natural Science Foundation of ChinaProject(2009AA044205) supported by the National High Technology Research and Development ProgramProject(BK2008043) supported by the Jiangsu Provincial Natural Science Foundation,China
文摘The influences of the mask wall angle on the current density distribution,shape of the evolving cavity and machining accuracy were investigated in electrochemical machining(ECM) by mask.A mathematical model was developed to predict the shape evolution during the ECM by mask.The current density distribution is sensitive to mask wall angle.The evolution of cavity is determined by the current density distribution of evolving workpiece surface.The maximum depth is away from the center of holes machined,which leads to the island appearing at the center of cavity for mask wall angles greater than or equal to 90°(β≥90°).The experimental system was established and the simulation results were experimentally verified.The results indicate that the simulation results of cavity shape are consistent with the actual ones.The experiments also show that the repetition accuracy of matrix-hole for β≥90° is higher than that for β<90°.A hole taper is diminished,and the machining accuracy is improved with the mask wall angle increasing.
基金Supported by the National High Technology Research and Development Program of China (2006AA05Z148)
文摘This article aims to investigate the transient behavior of a planar direct internal reforming solid oxide fuel cell （DIR-SOFC） comprehensively. A one-dimensional dynamic model of a planar D1R-SOFC is first developed based on mass and energy balances, and electrochemical principles. Further, a solution strategy is presented to solve the model, and the International Energy Agency （IEA） benchmark test is used to validate the model. Then, through model-based simulations, the steady-state performance of a co-flow planar DIR-SOFC under specified initial operating conditions and its dynamic response to introduced operating parameter disturbances are studied. The dynamic responses of important SOFC variables, such as cell temperature, current density, and cell voltage are all investigated when the SOFC is subjected to the step-changes in various operating parameters including both the load current and the inlet fuel and air flow rates. The results indicate that the rapid dynamics of the current density and the cell voltage are mainly influenced by the gas composition, particularly the H2 molar fraction in anode gas channels, while their slow dynamics are both dominated by the SOLID （including the PEN and interconnects） temperature. As the load current increases, the SOLID temperature and the maximum SOLID temperature gradient both increase, and thereby, the cell breakdown is apt to occur because of excessive thermal stresses. Changing the inlet fuel flow rate might lead to the change in the anode gas composition and the consequent change in the current density distribution and cell voltage. The inlet air flow rate has a great impact on the cell temperature distribution along the cell, and thus, is a suitable manipulated variable to control the cell temperature.
文摘A plane-symmetric inhomogeneous cosmological model of perfect fluid distribution with electro-magnetic field is obtained. F12 is the non-vanishing component of electromagnetic field tensor. To get a deterministic solution, we assume the free gravitational field is Petrov type-Ⅱ non-degenerate. Some physical and geometric properties of the model are also discussed.
