一、引言硅平面双极晶体管自问世以来,其频率和功率性能不断提高,发展迅速。但是,当频率提高到 C 波段或 C 波段以上时,由于其频率性能的继续提高与输出功率、散热性能、二次击穿性能以及封装后的寄生参数等等都发生了尖锐的矛盾,器件...一、引言硅平面双极晶体管自问世以来,其频率和功率性能不断提高,发展迅速。但是,当频率提高到 C 波段或 C 波段以上时,由于其频率性能的继续提高与输出功率、散热性能、二次击穿性能以及封装后的寄生参数等等都发生了尖锐的矛盾,器件的输出功率、增益和集电极效率随着工作频率的升高而急剧下降,明显地超出每倍频程下降6分贝的传统概念。于是,硅微波功率晶体管向 C 波段以上的更高频率的发展变得缓慢起来。展开更多
The channel lateral pocket or halo region of NMOSFET characterized by interface state R G current of a forward gated diode has been investigated numerically for the first time.The result of numerical analysis demons...The channel lateral pocket or halo region of NMOSFET characterized by interface state R G current of a forward gated diode has been investigated numerically for the first time.The result of numerical analysis demonstrates that the effective surface doping concentration and the interface state density of the pocket or halo region are interface states R G current peak position dependent and amplitude dependent,respectively.It can be expressed quantitatively according to the device physics knowledge,thus,the direct characterization of the interface state density and the effective surface doping concentration of the pocket or halo becomes very easy.展开更多
The current distributions over carbon steel under iron red alkyd primer exposed to 3.5% sodium chloride solution were mapped using the wire beam electrode （WBE）. The electrochemical impedance spectroscopy （EIS） of...The current distributions over carbon steel under iron red alkyd primer exposed to 3.5% sodium chloride solution were mapped using the wire beam electrode （WBE）. The electrochemical impedance spectroscopy （EIS） of the WBE was carded out to analyze the performance of coating delamination and corrosion behavior of carbon steel beneath defective coating. The EIS data revealed that protective capability of coating decreased with immersion time and the degree of cathodic delamination showed a rapid rise. The current density distribution of WBE indicated that cathodic sites was located at the defect at the beginning of immersion and gradually spread into the intact coating. The cathodic regions were distinguished from the anodic area and distributed over the WBE. The changes of cathodic sites could reflect the deterioration process of defective coating. The cathodic area ratio was a more useful parameter than the cathodic delamination degree to evaluate the coating cathodic delamination. The polarity reversals of electrodes at the defect and beneath coating were observed. A simple discussion of relationship between the blister and the polarity reversal was made from a standpoint of electrochemical distribution. WBE method was able to map and record the changes of local cathodic sites beneath defective coating in real time, which could provide more detailed information about the local degradation of coating.展开更多
We propose and study a spin-orbit interaction based mechanism to actively cool down the torsional vibrationof a nanomechanical resonator made by semiconductor materials.We show that the spin-orbit interactions of elec...We propose and study a spin-orbit interaction based mechanism to actively cool down the torsional vibrationof a nanomechanical resonator made by semiconductor materials.We show that the spin-orbit interactions of electronscan induce a coherent coupling between the electron spins and the torsional modes of nanomechanical vibration.Thiscoupling leads to an active cooling for the torsional modes through the dynamical thermalization of the resonator by thespin ensemble.展开更多
An on-axis holographic zone plate or an off-axis holographic zone plate used for the silicon solar cell will have a solar energy conversion factor of 2. 5. And the combination of the two plates will have its conversio...An on-axis holographic zone plate or an off-axis holographic zone plate used for the silicon solar cell will have a solar energy conversion factor of 2. 5. And the combination of the two plates will have its conversion factor of 5. Especially for the use of silver halide photographic emulsion, the cost can be cut down dramatically.展开更多
The silicon PN junction photodiode with very small sensitive area has been investigated.The device gets superhigh light current density J LS counted by the sensitive area in the planar PN junction.The superhi...The silicon PN junction photodiode with very small sensitive area has been investigated.The device gets superhigh light current density J LS counted by the sensitive area in the planar PN junction.The superhigh light current density is due to the light current transferred by the photogenerated minority carriers in the area around edges of the dopant diffused region.Then,we can determine the diffusion length of the photogenerated minority carriers in the substance by measuring the light current of the PN junction photodiode with very small sensitive area.展开更多
A novel electrode design for the in situ generation of ozone in the reaction zone of a tubular reactor is described in this work.The ozone generator uses a porous inner electrode tube in the corona discharge assembly,...A novel electrode design for the in situ generation of ozone in the reaction zone of a tubular reactor is described in this work.The ozone generator uses a porous inner electrode tube in the corona discharge assembly,and the ozone generated around the outer periphery of the porous tube diffuses into the tubular reactor and reacts with the contaminants in the fluid that is being treated.A mathematical model that includes absorption and second order reaction in the film is developed to describe ozonation kinetics of a contaminant dye in the tubular reactor.The model describes the experimental data for dye decolorization,oxidation byproducts,dissolved ozone,and ozone gas concentrations well.Model analysis indicates that the fast dye decolorization reaction occurs partly in the liquid film and partly in the bulk fluid.The model can be used in the selection of appropriate gas-liquid contactors for efficient oxidation of contaminants in effluents.展开更多
In the frame of the ZeuS-Ill project, a model study was started on evaluation the area-specific resistances （ASRs） of various layers being used in SOFC stacks. It is well known that stack performance not only depend...In the frame of the ZeuS-Ill project, a model study was started on evaluation the area-specific resistances （ASRs） of various layers being used in SOFC stacks. It is well known that stack performance not only depends on cell resistance but also on the electrical conductivity of the various applied contact and protective layers. Various layers have been tested under simulated SOFC conditions, and results have shown that the lowest ASR value, about 3 mΩ.cm2, was obtained for an LSM （2） contact layer. A significantly higher resistance was found for the combined contact and protective layer LCC10-Mn3O4, being around 37 mΩ.cm2 Related to the various tests, the total ASR of an F-design stack, developed by Forschungszentrum Jiilich, under ideal conditions can be estimated. In this case the ASR value was calculated as the sum of that of the LCC10-Mn3O4 layer and the formed oxide scale due to oxidation of Crofer22APU. Contacting resistance at the anode side was considered negligible. When differences in the ASR values occurred when compared with that from current-voltage measurements performed with real SOFC stacks, this can be explained by the limited contact area between interconnect and cathode. These results can be used to model the influence of various applied layers and different geometric contact areas on the overall ASR as determined from performance measurements with SOFC stacks.展开更多
The classical Ekman theory tells us that the ocean surface current turns to the right(left) side of wind direction with 45° in the north(south) hemisphere,but the observation and research results show that the su...The classical Ekman theory tells us that the ocean surface current turns to the right(left) side of wind direction with 45° in the north(south) hemisphere,but the observation and research results show that the surface current deflexion angle is smaller than 45° in the Arctic and high latitude areas while larger than 45° in the low latitude areas.In order to explain these phenomena,a series of idealized numerical experiments are designed to investigate the influence of vertical viscosity coefficients with different vertical distribution characteristics on the classical and steady Ekman spiral structure.Results show that when the vertical viscosity coefficient decreases with water depth,the surface current deflexion angle is larger than 45°,whereas the angle is smaller than 45° when the vertical viscosity coefficient increases with water depth.So the different observed surface current deflexion angles in low latitude sea areas and the Arctic regions should be attributed to the different vertical distribution characteristics of vertical viscosity coefficients in the upper ocean.The flatness of the Ekman spiral is not equal to one and does not show regular behaviors for the numerical experiments with different distribution of vertical viscosity.However,the magnitudes and directions of volume transport of Ekman spirals are almost the same as the results of classical Ekman theory,i.e.,vertical viscosity coefficient distributions have no effect on the magnitudes and directions of volume transport.展开更多
文摘一、引言硅平面双极晶体管自问世以来,其频率和功率性能不断提高,发展迅速。但是,当频率提高到 C 波段或 C 波段以上时,由于其频率性能的继续提高与输出功率、散热性能、二次击穿性能以及封装后的寄生参数等等都发生了尖锐的矛盾,器件的输出功率、增益和集电极效率随着工作频率的升高而急剧下降,明显地超出每倍频程下降6分贝的传统概念。于是,硅微波功率晶体管向 C 波段以上的更高频率的发展变得缓慢起来。
文摘The channel lateral pocket or halo region of NMOSFET characterized by interface state R G current of a forward gated diode has been investigated numerically for the first time.The result of numerical analysis demonstrates that the effective surface doping concentration and the interface state density of the pocket or halo region are interface states R G current peak position dependent and amplitude dependent,respectively.It can be expressed quantitatively according to the device physics knowledge,thus,the direct characterization of the interface state density and the effective surface doping concentration of the pocket or halo becomes very easy.
基金supported by the National Natural Science Foundation of China (Grant No. 51131005)
文摘The current distributions over carbon steel under iron red alkyd primer exposed to 3.5% sodium chloride solution were mapped using the wire beam electrode （WBE）. The electrochemical impedance spectroscopy （EIS） of the WBE was carded out to analyze the performance of coating delamination and corrosion behavior of carbon steel beneath defective coating. The EIS data revealed that protective capability of coating decreased with immersion time and the degree of cathodic delamination showed a rapid rise. The current density distribution of WBE indicated that cathodic sites was located at the defect at the beginning of immersion and gradually spread into the intact coating. The cathodic regions were distinguished from the anodic area and distributed over the WBE. The changes of cathodic sites could reflect the deterioration process of defective coating. The cathodic area ratio was a more useful parameter than the cathodic delamination degree to evaluate the coating cathodic delamination. The polarity reversals of electrodes at the defect and beneath coating were observed. A simple discussion of relationship between the blister and the polarity reversal was made from a standpoint of electrochemical distribution. WBE method was able to map and record the changes of local cathodic sites beneath defective coating in real time, which could provide more detailed information about the local degradation of coating.
基金NSFC under Grant Nos.90203018,10474104,10574077,and 60433050NFRPC under Grant Nos.2006CB921206,2006CBOL0601,2006AA06Z104,and 2005CB724508
文摘We propose and study a spin-orbit interaction based mechanism to actively cool down the torsional vibrationof a nanomechanical resonator made by semiconductor materials.We show that the spin-orbit interactions of electronscan induce a coherent coupling between the electron spins and the torsional modes of nanomechanical vibration.Thiscoupling leads to an active cooling for the torsional modes through the dynamical thermalization of the resonator by thespin ensemble.
文摘An on-axis holographic zone plate or an off-axis holographic zone plate used for the silicon solar cell will have a solar energy conversion factor of 2. 5. And the combination of the two plates will have its conversion factor of 5. Especially for the use of silver halide photographic emulsion, the cost can be cut down dramatically.
文摘The silicon PN junction photodiode with very small sensitive area has been investigated.The device gets superhigh light current density J LS counted by the sensitive area in the planar PN junction.The superhigh light current density is due to the light current transferred by the photogenerated minority carriers in the area around edges of the dopant diffused region.Then,we can determine the diffusion length of the photogenerated minority carriers in the substance by measuring the light current of the PN junction photodiode with very small sensitive area.
基金Supported in part by a research grant(BES-0209343) from the U.S.National Science Foundation
文摘A novel electrode design for the in situ generation of ozone in the reaction zone of a tubular reactor is described in this work.The ozone generator uses a porous inner electrode tube in the corona discharge assembly,and the ozone generated around the outer periphery of the porous tube diffuses into the tubular reactor and reacts with the contaminants in the fluid that is being treated.A mathematical model that includes absorption and second order reaction in the film is developed to describe ozonation kinetics of a contaminant dye in the tubular reactor.The model describes the experimental data for dye decolorization,oxidation byproducts,dissolved ozone,and ozone gas concentrations well.Model analysis indicates that the fast dye decolorization reaction occurs partly in the liquid film and partly in the bulk fluid.The model can be used in the selection of appropriate gas-liquid contactors for efficient oxidation of contaminants in effluents.
文摘In the frame of the ZeuS-Ill project, a model study was started on evaluation the area-specific resistances （ASRs） of various layers being used in SOFC stacks. It is well known that stack performance not only depends on cell resistance but also on the electrical conductivity of the various applied contact and protective layers. Various layers have been tested under simulated SOFC conditions, and results have shown that the lowest ASR value, about 3 mΩ.cm2, was obtained for an LSM （2） contact layer. A significantly higher resistance was found for the combined contact and protective layer LCC10-Mn3O4, being around 37 mΩ.cm2 Related to the various tests, the total ASR of an F-design stack, developed by Forschungszentrum Jiilich, under ideal conditions can be estimated. In this case the ASR value was calculated as the sum of that of the LCC10-Mn3O4 layer and the formed oxide scale due to oxidation of Crofer22APU. Contacting resistance at the anode side was considered negligible. When differences in the ASR values occurred when compared with that from current-voltage measurements performed with real SOFC stacks, this can be explained by the limited contact area between interconnect and cathode. These results can be used to model the influence of various applied layers and different geometric contact areas on the overall ASR as determined from performance measurements with SOFC stacks.
基金supported by the National Natural Science Foundation of China(Grant No.40876015)the Project of Comprehensive Evaluation of Polar Areas on Global and Regional Climate Changes(Grant No.CHINARE2012-04-04)
文摘The classical Ekman theory tells us that the ocean surface current turns to the right(left) side of wind direction with 45° in the north(south) hemisphere,but the observation and research results show that the surface current deflexion angle is smaller than 45° in the Arctic and high latitude areas while larger than 45° in the low latitude areas.In order to explain these phenomena,a series of idealized numerical experiments are designed to investigate the influence of vertical viscosity coefficients with different vertical distribution characteristics on the classical and steady Ekman spiral structure.Results show that when the vertical viscosity coefficient decreases with water depth,the surface current deflexion angle is larger than 45°,whereas the angle is smaller than 45° when the vertical viscosity coefficient increases with water depth.So the different observed surface current deflexion angles in low latitude sea areas and the Arctic regions should be attributed to the different vertical distribution characteristics of vertical viscosity coefficients in the upper ocean.The flatness of the Ekman spiral is not equal to one and does not show regular behaviors for the numerical experiments with different distribution of vertical viscosity.However,the magnitudes and directions of volume transport of Ekman spirals are almost the same as the results of classical Ekman theory,i.e.,vertical viscosity coefficient distributions have no effect on the magnitudes and directions of volume transport.
