To simulate steady airflows inside of wall-flow diesel particulate filters (DPF) with different reverse blowing pipes collocation, a mathematical model of the flow in a DPF is established by an equivalent continuum ...To simulate steady airflows inside of wall-flow diesel particulate filters (DPF) with different reverse blowing pipes collocation, a mathematical model of the flow in a DPF is established by an equivalent continuum approach. The experimental results agree well with the theoretical values calculated from the model. Simulation shows that the velocity and the pressure distribution of the filters in the regenerative process are key factors to the filter's regeneration. How to decrease the mal-distribution of the flow in the filter and how to achieve the better regenerative performance at the least cost of air consumption in the regenerative process are the ultimate goals of the study. Calculation and experiments show that the goals can be realized through adjusting the angle of two reverse blowing pipes and their relative location suitably.展开更多
A new analytical model for reverse characteristics of 4H-SiC merged PN Sehottky diodes (MPS or 3BS) is developed. To accurately calculate the reverse characteristics of the 4H SiC MPS diode, the relationship between...A new analytical model for reverse characteristics of 4H-SiC merged PN Sehottky diodes (MPS or 3BS) is developed. To accurately calculate the reverse characteristics of the 4H SiC MPS diode, the relationship between the electric field at the Schottky contact and the reverse bias is analytically established by solving the cylindrical Poisson equation after the channel has pinched off. The reverse current density calculated from the Wentzel-Kramers-Brillouin (WKB) theory is verified by comparing it with the experimental result, showing that they are in good agreement with each other. Moreover, the effects of P-region spacing (S) and P-junction depth (Xj) on the characteristics of 4H-SiC MPS are analysed, and are particularly useful for optimizing the design of the high voltage MPS diodes.展开更多
A new SiC superjunction power MOSFET device using high-k insulator and p-type pillar with an integrated Schottky barrier diode(Hk-SJ-SBD MOSFET)is proposed,and has been compared with the SiC high-k MOSFET(Hk MOSFET),S...A new SiC superjunction power MOSFET device using high-k insulator and p-type pillar with an integrated Schottky barrier diode(Hk-SJ-SBD MOSFET)is proposed,and has been compared with the SiC high-k MOSFET(Hk MOSFET),SiC superjuction MOSFET(SJ MOSFET)and the conventional SiC MOSFET in this article.In the proposed SiC Hk-SJ-SBD MOSFET,under the combined action of the p-type region and the Hk dielectric layer in the drift region,the concentration of the N-drift region and the current spreading layer can be increased to achieve an ultra-low specific on-resistance(Ron,sp).The integrated Schottky barrier diode(SBD)also greatly improves the reverse recovery performance of the device.TCAD simulation results indicate that the Ron,sp of the proposed SiC Hk-SJ-SBD MOSFET is 0.67 mΩ·cm^(2)with a 2240 V breakdown voltage(BV),which is more than 72.4%,23%,5.6%lower than that of the conventional SiC MOSFET,Hk SiC MOSFET and SJ SiC MOSFET with the 1950,2220,and 2220V BV,respectively.The reverse recovery time and reverse recovery charge of the proposed MOSFET is 16 ns and18 nC,which are greatly reduced by more than 74%and 94%in comparison with those of all the conventional SiC MOSFET,Hk SiC MOSFET and SJ SiC MOSFET,due to the integrated SBD in the proposed MOSFET.And the trade-off relationship between the Ron,sp and the BV is also significantly improved compared with that of the conventional MOSFET,Hk MOSFET and SJ MOSFET as well as the MOSFETs in other previous literature,respectively.In addition,compared with conventional SJ SiC MOSFET,the proposed SiC MOSFET has better immunity to charge imbalance,which may bring great application prospects.展开更多
The nonlinear J-E characteristics under self-heating equilibrium for conductive composites based on high density polyethylene were studied. The results show that there are identical conduction mechanisms under self-he...The nonlinear J-E characteristics under self-heating equilibrium for conductive composites based on high density polyethylene were studied. The results show that there are identical conduction mechanisms under self-heating equilibrium for the composites with various initial resistivities determined by filler content or ambient temperature. The nonlinear conduction behavior was involved in the limited microstructure transformations of the conducting network induced by electrical field applied and the corresponding self-heating effect. A reversible thermal fuse (RTF) model was suggested to interpret the physical origin of the nonlinear J-E characteristics.展开更多
Recently abiogenic alkanes have been found in various locations in the world and other celestial bodies. The chemical composition of abiogenic alkane gases varies widely. The content of methane is low and nearly no C2...Recently abiogenic alkanes have been found in various locations in the world and other celestial bodies. The chemical composition of abiogenic alkane gases varies widely. The content of methane is low and nearly no C2+ is found in the abiogenic alkane gases from fluid inclusions in volcanic rocks or hot springs in China. In the unsedimented submarine hydrothermal vent system C1/C2+ ratios are much greater than those for the thermogenic gases, mostly >800 and in some cases up to 8,000. In the Songliao Basin, China, C1/C2+ of some abiogenic gases are often less than 150. Abiogenic alkane gases which have been found in nature often have carbon isotopic reversal among C1–C4 alkanes (δ13C1>δ13C2>δ13C3>δ13C4), whereas both regular and reversed hydrogen isotope distribution pattern among C1–C4 alkanes have been reported. The δ13C of abiogenic methane is mainly greater than ?30‰ though laboratory synthesized methane can have δ13C as low as ?57‰, and its δD1 values vary widely and overlap with biogenic gases. High 3He/4He ratios often indicate the addition of mantle-derived helium and are related to abiogenic gases. However, some biogenic gases can also have high 3He/4He ratios up to 8. The CH4/3He end-member is often lower than 106 for abiogenic alkane gases while greater than 1013 for biogenic gases, and the values between these two end-members often reflect the mixing of biogenic and abiogenic gases.展开更多
Several parameters of a commercial Si-based Schottky barrier diode (SBD) with unknown metal material and semiconductor-type have been investigated in this work from dark forward and reverse I-V characteristics in the ...Several parameters of a commercial Si-based Schottky barrier diode (SBD) with unknown metal material and semiconductor-type have been investigated in this work from dark forward and reverse I-V characteristics in the temperature (T) range of [274.5 K - 366.5 K]. Those parameters include the reverse saturation current (I<sub>s</sub>), the ideality factor (n), the series and the shunt resistances (R<sub>s</sub> and R<sub>sh</sub>), the effective and the zero bias barrier heights (Φ<sub>B</sub> and Φ<sub>B0</sub>), the product of the electrical active area (A) and the effective Richardson constant (A**), the built-in potential (V<sub>bi</sub>), together with the semiconductor doping concentration (N<sub>A</sub> or N<sub>D</sub>). Some of them have been extracted by using two or three different methods. The main features of each approach have been clearly stated. From one parameter to another, results have been discussed in terms of structure performance, comparison on one another when extracted from different methods, accordance or discordance with data from other works, and parameter’s temperature or voltage dependence. A comparison of results on Φ<sub>B</sub>, ΦB0</sub>, n and N<sub>A</sub> or N<sub>D</sub> parameters with some available data in literature for the same parameters, has especially led to clear propositions on the identity of the analyzed SBD’s metal and semiconductor-type.展开更多
The thin emitter structure was introduced into reversely switched dynistor(RSD) to improve its turn-on characteristics. According to the analysis of turn-on condition, thin emitter structure is capable of reducing the...The thin emitter structure was introduced into reversely switched dynistor(RSD) to improve its turn-on characteristics. According to the analysis of turn-on condition, thin emitter structure is capable of reducing the extraction action for the triggering plasma layer P1 during turn-on process, and satisfying the requirement that triggering electric charge cannot be exhausted and therefore enables RSD to turn on uniformly. The on-state thin emitter RSD was equivalent to an asymmetric pin diode model. The simulation result shows that the forward voltage drop of RSD falls with the decrease of doping dose in p+-emitter in a certain range, and when the doping concentration is extremely low, the decrease of the width of p+-emitter can obtain a low forward voltage drop. Thin emitter RSD chips were made by sintering Al on n-Si. The test result shows that their turn-on process is uniform and the voltage drop is 7.5 V when the peak conversion current is 5 500 A.展开更多
基金This project is supported by National Hi-tech Research and DevelopmentProgram of China (863 Program, No.2003AA643010B).
文摘To simulate steady airflows inside of wall-flow diesel particulate filters (DPF) with different reverse blowing pipes collocation, a mathematical model of the flow in a DPF is established by an equivalent continuum approach. The experimental results agree well with the theoretical values calculated from the model. Simulation shows that the velocity and the pressure distribution of the filters in the regenerative process are key factors to the filter's regeneration. How to decrease the mal-distribution of the flow in the filter and how to achieve the better regenerative performance at the least cost of air consumption in the regenerative process are the ultimate goals of the study. Calculation and experiments show that the goals can be realized through adjusting the angle of two reverse blowing pipes and their relative location suitably.
基金Project supported by the Xi’an Applied Materials Innovation Fund (Grant No XA-AM-200702)
文摘A new analytical model for reverse characteristics of 4H-SiC merged PN Sehottky diodes (MPS or 3BS) is developed. To accurately calculate the reverse characteristics of the 4H SiC MPS diode, the relationship between the electric field at the Schottky contact and the reverse bias is analytically established by solving the cylindrical Poisson equation after the channel has pinched off. The reverse current density calculated from the Wentzel-Kramers-Brillouin (WKB) theory is verified by comparing it with the experimental result, showing that they are in good agreement with each other. Moreover, the effects of P-region spacing (S) and P-junction depth (Xj) on the characteristics of 4H-SiC MPS are analysed, and are particularly useful for optimizing the design of the high voltage MPS diodes.
基金supported in part by the National Natural Science Foundation of China(Grant No.61974015)Key R&D Project of Science and Technology Plan of the Sichuan province(Grant No.2021YFG0139)the Open Foundation of State Key Laboratory of Electronic Thin Films and Integrated Devices of China(Grant No.KFJJ201806)。
文摘A new SiC superjunction power MOSFET device using high-k insulator and p-type pillar with an integrated Schottky barrier diode(Hk-SJ-SBD MOSFET)is proposed,and has been compared with the SiC high-k MOSFET(Hk MOSFET),SiC superjuction MOSFET(SJ MOSFET)and the conventional SiC MOSFET in this article.In the proposed SiC Hk-SJ-SBD MOSFET,under the combined action of the p-type region and the Hk dielectric layer in the drift region,the concentration of the N-drift region and the current spreading layer can be increased to achieve an ultra-low specific on-resistance(Ron,sp).The integrated Schottky barrier diode(SBD)also greatly improves the reverse recovery performance of the device.TCAD simulation results indicate that the Ron,sp of the proposed SiC Hk-SJ-SBD MOSFET is 0.67 mΩ·cm^(2)with a 2240 V breakdown voltage(BV),which is more than 72.4%,23%,5.6%lower than that of the conventional SiC MOSFET,Hk SiC MOSFET and SJ SiC MOSFET with the 1950,2220,and 2220V BV,respectively.The reverse recovery time and reverse recovery charge of the proposed MOSFET is 16 ns and18 nC,which are greatly reduced by more than 74%and 94%in comparison with those of all the conventional SiC MOSFET,Hk SiC MOSFET and SJ SiC MOSFET,due to the integrated SBD in the proposed MOSFET.And the trade-off relationship between the Ron,sp and the BV is also significantly improved compared with that of the conventional MOSFET,Hk MOSFET and SJ MOSFET as well as the MOSFETs in other previous literature,respectively.In addition,compared with conventional SJ SiC MOSFET,the proposed SiC MOSFET has better immunity to charge imbalance,which may bring great application prospects.
基金the National Advanced Material Committee of China (NAMCC),国家自然科学基金
文摘The nonlinear J-E characteristics under self-heating equilibrium for conductive composites based on high density polyethylene were studied. The results show that there are identical conduction mechanisms under self-heating equilibrium for the composites with various initial resistivities determined by filler content or ambient temperature. The nonlinear conduction behavior was involved in the limited microstructure transformations of the conducting network induced by electrical field applied and the corresponding self-heating effect. A reversible thermal fuse (RTF) model was suggested to interpret the physical origin of the nonlinear J-E characteristics.
基金supported by the China Postdoctoral Science Foundation (20070420393)China Postdoctoral Special Science Foundation (20081095)PetroChina Science and Technology Project (07-01C-01-07)
文摘Recently abiogenic alkanes have been found in various locations in the world and other celestial bodies. The chemical composition of abiogenic alkane gases varies widely. The content of methane is low and nearly no C2+ is found in the abiogenic alkane gases from fluid inclusions in volcanic rocks or hot springs in China. In the unsedimented submarine hydrothermal vent system C1/C2+ ratios are much greater than those for the thermogenic gases, mostly >800 and in some cases up to 8,000. In the Songliao Basin, China, C1/C2+ of some abiogenic gases are often less than 150. Abiogenic alkane gases which have been found in nature often have carbon isotopic reversal among C1–C4 alkanes (δ13C1>δ13C2>δ13C3>δ13C4), whereas both regular and reversed hydrogen isotope distribution pattern among C1–C4 alkanes have been reported. The δ13C of abiogenic methane is mainly greater than ?30‰ though laboratory synthesized methane can have δ13C as low as ?57‰, and its δD1 values vary widely and overlap with biogenic gases. High 3He/4He ratios often indicate the addition of mantle-derived helium and are related to abiogenic gases. However, some biogenic gases can also have high 3He/4He ratios up to 8. The CH4/3He end-member is often lower than 106 for abiogenic alkane gases while greater than 1013 for biogenic gases, and the values between these two end-members often reflect the mixing of biogenic and abiogenic gases.
文摘Several parameters of a commercial Si-based Schottky barrier diode (SBD) with unknown metal material and semiconductor-type have been investigated in this work from dark forward and reverse I-V characteristics in the temperature (T) range of [274.5 K - 366.5 K]. Those parameters include the reverse saturation current (I<sub>s</sub>), the ideality factor (n), the series and the shunt resistances (R<sub>s</sub> and R<sub>sh</sub>), the effective and the zero bias barrier heights (Φ<sub>B</sub> and Φ<sub>B0</sub>), the product of the electrical active area (A) and the effective Richardson constant (A**), the built-in potential (V<sub>bi</sub>), together with the semiconductor doping concentration (N<sub>A</sub> or N<sub>D</sub>). Some of them have been extracted by using two or three different methods. The main features of each approach have been clearly stated. From one parameter to another, results have been discussed in terms of structure performance, comparison on one another when extracted from different methods, accordance or discordance with data from other works, and parameter’s temperature or voltage dependence. A comparison of results on Φ<sub>B</sub>, ΦB0</sub>, n and N<sub>A</sub> or N<sub>D</sub> parameters with some available data in literature for the same parameters, has especially led to clear propositions on the identity of the analyzed SBD’s metal and semiconductor-type.
基金National Natural Science Foundation of China(No.50277016 and 50577028)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20050487044)
文摘The thin emitter structure was introduced into reversely switched dynistor(RSD) to improve its turn-on characteristics. According to the analysis of turn-on condition, thin emitter structure is capable of reducing the extraction action for the triggering plasma layer P1 during turn-on process, and satisfying the requirement that triggering electric charge cannot be exhausted and therefore enables RSD to turn on uniformly. The on-state thin emitter RSD was equivalent to an asymmetric pin diode model. The simulation result shows that the forward voltage drop of RSD falls with the decrease of doping dose in p+-emitter in a certain range, and when the doping concentration is extremely low, the decrease of the width of p+-emitter can obtain a low forward voltage drop. Thin emitter RSD chips were made by sintering Al on n-Si. The test result shows that their turn-on process is uniform and the voltage drop is 7.5 V when the peak conversion current is 5 500 A.