The fabrication and characterization of 1700 V 7 A 4H-SiC vertical double-implanted metal-oxide-semiconductor field-effect transistors （VDMOSFETs） are reported. The drift layer is 17μm in thickness with 5 × 10...The fabrication and characterization of 1700 V 7 A 4H-SiC vertical double-implanted metal-oxide-semiconductor field-effect transistors （VDMOSFETs） are reported. The drift layer is 17μm in thickness with 5 × 10^15 cm^-3 n-type doping, and the channel length is 1μm. The MOSFETs show a peak mobility of 17cm2/V.s and a typical threshold voltage of 3 V. The active area of 0.028cm2 delivers a forward drain current of 7A at Vcs = 22 V and VDS= 15 V. The specific on-resistance （Ron,sv） is 18mΩ.cm2 at VGS= 22 V and the blocking voltage is 1975 V （IDS 〈 lOOnA） at VGS = 0 V.展开更多
The interaction of L-Aspartic acid （Asp） with Vctoria Green S （VGS） in pH 6.0 Britton-Robinson buffer solution has been investigated by UV/Vis spectropbotometry and resonance light scattering （RLS） technique. Th...The interaction of L-Aspartic acid （Asp） with Vctoria Green S （VGS） in pH 6.0 Britton-Robinson buffer solution has been investigated by UV/Vis spectropbotometry and resonance light scattering （RLS） technique. The non-covalent interactions such as hydrogen bond, salt linkage and hydrophobic bond were proposed to explain the interaction between VGS and Asp. It indicated that Asp could link each other to form a long chain by salt linkages and hydrogen bonds in aqueous medium. Then the long chain surrounded the hydrophobic groups of VGS via hydrophobic interaction and reacted with VGS by salt linkages and hydrogen bonds to form a macromolecular aggregation. The aggregation was much bigger than VGS itself. So the color became deeper and the system＇s absorption and RLS intensity increased. The increase in the absorbance at 617nm was proportional to the concentration of Asp, providing a basis for the quantitative determination of Asp. This method was simple and efficient than the ordinary methods and had been applied to the direct determination of Asp with satisfactory results.展开更多
Vertical greening systems(VGS)are promising green infrastructure(GI)techniques for addressing urban resilience issues,like mitigating high temperatures and air pollution.This research aims to develop a conceptual fram...Vertical greening systems(VGS)are promising green infrastructure(GI)techniques for addressing urban resilience issues,like mitigating high temperatures and air pollution.This research aims to develop a conceptual framework to help designers better understand the VGS’effects on buildings and urban areas,focusing on thermal performance and air quality improvement in hot,humid climates.The framework consists of three steps:(1)Identifying climate problems that hinder the improvement of built environment resilience in hot climates;(2)Selecting VGS as a type of GI that can enhance urban resilience;(3)Identifying the common key factors that impact both thermal performance and air quality while developing VGS at the urban and building scales.The results show that the framework can be customized to suit hot climate conditions.However,when applying VGS in built environment with specified climate conditions,the construction of VGS,greenery coverage ratio,plant species,facade orientation,and VGS formation have the most significant influences on their environmental performance.Additionally,the air gap between VGS and the facade has optimal performance in hot,humid climates.The paper concludes with some recommendations for future research and practice on VGSs in hot and humid climates.展开更多
Inter-turn short circuit of field windings is a common electrical fault of generators.Simulation is an important method of investigating the fault and providing data support for fault monitoring.However,huge numbers o...Inter-turn short circuit of field windings is a common electrical fault of generators.Simulation is an important method of investigating the fault and providing data support for fault monitoring.However,huge numbers of pole pairs and damper loops in large hydro-generators would lead to lengthy calculation time,hindering scientific research and engineering application.To deal with this problem,we analyze a theoretical basis for a damper winding simplified model and then propose an equivalent treatment method.Through the analysis of steady-state current harmonic characteristics of generators with different stator winding configurations during the fault,the simplified models suitable for steady-state calculation are derived from two aspects,namely,additional rotor harmonic current frequency characteristics and the relationship of the amplitude as well as the phase of each branch current of the stator.The calculation and experimental results of the two simplified models are then compared to verify the models' correctness.A calculation example of the Three Gorges left bank VGS generator shows few deviations between the calculation results of the simplified model and the original model.Moreover,the calculation time using the simplified model is 1/1500 that using the original model,which provides a more effective tool for on-line fault monitoring.Finally,the sensitivity-verification application of the fault-monitoring scheme based on the stator steady-state unbalanced current RMS is depicted.The result shows that the scheme can monitor two-turn short circuits of field windings in the Three Gorges generator and provide high sensitivity.展开更多
基金Supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China under Grant No 2013ZX02305
文摘The fabrication and characterization of 1700 V 7 A 4H-SiC vertical double-implanted metal-oxide-semiconductor field-effect transistors （VDMOSFETs） are reported. The drift layer is 17μm in thickness with 5 × 10^15 cm^-3 n-type doping, and the channel length is 1μm. The MOSFETs show a peak mobility of 17cm2/V.s and a typical threshold voltage of 3 V. The active area of 0.028cm2 delivers a forward drain current of 7A at Vcs = 22 V and VDS= 15 V. The specific on-resistance （Ron,sv） is 18mΩ.cm2 at VGS= 22 V and the blocking voltage is 1975 V （IDS 〈 lOOnA） at VGS = 0 V.
基金Acknowledgements： This work was supported by the Natural Science Foundation of Anhui Province （No. 2006K J128B） and the Young Teacher Natural Science Foundation of Anhui Province Commission （No. 2006jp 1139）.
文摘The interaction of L-Aspartic acid （Asp） with Vctoria Green S （VGS） in pH 6.0 Britton-Robinson buffer solution has been investigated by UV/Vis spectropbotometry and resonance light scattering （RLS） technique. The non-covalent interactions such as hydrogen bond, salt linkage and hydrophobic bond were proposed to explain the interaction between VGS and Asp. It indicated that Asp could link each other to form a long chain by salt linkages and hydrogen bonds in aqueous medium. Then the long chain surrounded the hydrophobic groups of VGS via hydrophobic interaction and reacted with VGS by salt linkages and hydrogen bonds to form a macromolecular aggregation. The aggregation was much bigger than VGS itself. So the color became deeper and the system＇s absorption and RLS intensity increased. The increase in the absorbance at 617nm was proportional to the concentration of Asp, providing a basis for the quantitative determination of Asp. This method was simple and efficient than the ordinary methods and had been applied to the direct determination of Asp with satisfactory results.
文摘Vertical greening systems(VGS)are promising green infrastructure(GI)techniques for addressing urban resilience issues,like mitigating high temperatures and air pollution.This research aims to develop a conceptual framework to help designers better understand the VGS’effects on buildings and urban areas,focusing on thermal performance and air quality improvement in hot,humid climates.The framework consists of three steps:(1)Identifying climate problems that hinder the improvement of built environment resilience in hot climates;(2)Selecting VGS as a type of GI that can enhance urban resilience;(3)Identifying the common key factors that impact both thermal performance and air quality while developing VGS at the urban and building scales.The results show that the framework can be customized to suit hot climate conditions.However,when applying VGS in built environment with specified climate conditions,the construction of VGS,greenery coverage ratio,plant species,facade orientation,and VGS formation have the most significant influences on their environmental performance.Additionally,the air gap between VGS and the facade has optimal performance in hot,humid climates.The paper concludes with some recommendations for future research and practice on VGSs in hot and humid climates.
基金supported by the National Natural Science Foundation of China (Grant No. 50807027)the China Postdoctoral Science Foundation(Grant No. 2012M520155)the Fundamental Research Funds for the Central Universities (Grant No. 2013JBM081)
文摘Inter-turn short circuit of field windings is a common electrical fault of generators.Simulation is an important method of investigating the fault and providing data support for fault monitoring.However,huge numbers of pole pairs and damper loops in large hydro-generators would lead to lengthy calculation time,hindering scientific research and engineering application.To deal with this problem,we analyze a theoretical basis for a damper winding simplified model and then propose an equivalent treatment method.Through the analysis of steady-state current harmonic characteristics of generators with different stator winding configurations during the fault,the simplified models suitable for steady-state calculation are derived from two aspects,namely,additional rotor harmonic current frequency characteristics and the relationship of the amplitude as well as the phase of each branch current of the stator.The calculation and experimental results of the two simplified models are then compared to verify the models' correctness.A calculation example of the Three Gorges left bank VGS generator shows few deviations between the calculation results of the simplified model and the original model.Moreover,the calculation time using the simplified model is 1/1500 that using the original model,which provides a more effective tool for on-line fault monitoring.Finally,the sensitivity-verification application of the fault-monitoring scheme based on the stator steady-state unbalanced current RMS is depicted.The result shows that the scheme can monitor two-turn short circuits of field windings in the Three Gorges generator and provide high sensitivity.
