The surge arrester with excellent protection characteristics would decrease the overvoltage level ap- plied on the power apparatus to reduce their insulation levels and manufacturing bottleneck. The arrester for the 1...The surge arrester with excellent protection characteristics would decrease the overvoltage level ap- plied on the power apparatus to reduce their insulation levels and manufacturing bottleneck. The arrester for the 1000-kV ultra-high voltage ac power transmission system is designed as tank-type structure. The field-circuit combination numerical method combining the three-dimensional finite element method with circuit is proposed to analyze the potential distribution of GIS arrester. By comparing several design schemes, the most effective method to improve the potential distribution along the varistor column is to increase the voltage gradient of the ZnO varistor. Synthesizing several influential factors, the suitable voltage gradient of ZnO varistor should be controlled to 435 V/mm, and the resulted nonuniform degree of the potential distribution along the varistor column inside the GIS arrester would be controlled smaller than 10%. The result in this paper provides the fundamental technical index for the study of the high voltage gradient ZnO varistors.展开更多
Effect of direct current electric field （DCEF） on corrosion behaviour of copper printed circuit board （PCB-Cu）, Cl-ion migration behaviour, dendrites growth under thin electrolyte layer was investigated using pote...Effect of direct current electric field （DCEF） on corrosion behaviour of copper printed circuit board （PCB-Cu）, Cl-ion migration behaviour, dendrites growth under thin electrolyte layer was investigated using potentiodynamic polarization and scanning electron microscopy （SEM） with energy dispersive spectrometer （EDS）. Results indicate that DCEF decreases the corrosion of PCB-Cu;Cl-ions directionally migrate from the negative pole to the positive pole, and enrich on the surface of the positive pole, which causes serious localized corrosion; dendrites grow on the surface of the negative pole, and the rate and scale of dendrite growth become faster and greater with the increase of external voltage and exposure time, respectively.展开更多
Metal-oxide-semiconductor field effect transistors(MOSFET)based on two-dimensional(2D)semiconductors have attracted extensive attention owing to their excellent transport properties,atomically thin geometry,and tunabl...Metal-oxide-semiconductor field effect transistors(MOSFET)based on two-dimensional(2D)semiconductors have attracted extensive attention owing to their excellent transport properties,atomically thin geometry,and tunable bandgaps.Besides improving the transistor performance of individual device,lots of efforts have been devoted to achieving 2D logic functions or integrated circuit towards practical application.In this review,we discussed the recent progresses of 2D-based logic circuit.We will first start with the different methods for realization of n-type metal-oxide-semiconductor(NMOS)-only(or p-type metal-oxide-semiconductor(PMOS)-only)logic circuit.Next,various device polarity control and complementary-metal-oxide-semiconductor(CMOS)approaches are summarized,including utilizing different 2D semiconductors with intrinsic complementary doping,charge transfer doping,contact engineering,and electrostatics doping.We will discuss the merits and drawbacks of each approach,and lastly conclude with a short perspective on the challenges and future developments of 2D logic circuit.展开更多
With research on the carrier phase synchronization and symbol synchronization algorithm of demodulation module, a synchronization circuit system is designed for GPS software receiver based on field programmable gate a...With research on the carrier phase synchronization and symbol synchronization algorithm of demodulation module, a synchronization circuit system is designed for GPS software receiver based on field programmable gate array （FPGA）, and a series of experiment is done on the hardware platform. The result shows the all-digital synchronization and demodulation of GPS intermediate frequency （IF） signal can be realized and applied in embedded real-time GPS software receiver system. It is verified that the decision-directed joint tracking algorithm of carrier phase and symbol timing for received signals from GPS is reasonable. In addition, the loop works steadily and can be used for receiving GPS signals using synchronous demodulation. The synchronization circuit for GPS software receiver designed based on FPGA has the features of low cost, miniaturization, low power and real-time. Surely, it will become one of the development directions for GPS and even GNSS embedded real-time software receiver.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
The electric field intensity (EFI) is important characteristic quantity for evaluating the internal insulation state of cable joints. Based on finite element method, this paper proposes two EFI research methods, field...The electric field intensity (EFI) is important characteristic quantity for evaluating the internal insulation state of cable joints. Based on finite element method, this paper proposes two EFI research methods, field-circuit coupling method and equivalent circuit method. The average EFI of the inner surface of the outer semi-conducting shield can be calculated from the current in the measuring circuit. The relative error between these two methods is about 15%, which roughly proves the consistency of the two methods. Further practical application research enables online monitoring of cable joints.展开更多
Reconfiguration is the key to produce an applicable ternary optical computer （TOC）. The method to implement the reconfiguration function determines whether a TOC can step into applied fields or not. In this work, a ...Reconfiguration is the key to produce an applicable ternary optical computer （TOC）. The method to implement the reconfiguration function determines whether a TOC can step into applied fields or not. In this work, a design of the reconfiguration circuit based on field programmable gates array （FPGA） is proposed, and the structure of the entire hardware system is discussed.展开更多
基金Supported by the National Nature Science Foundation of China (Grant Nos.50425721,5073001)the 11th Five-year National S&T Supporting Plan (Grant No.2006BAA02A16)
文摘The surge arrester with excellent protection characteristics would decrease the overvoltage level ap- plied on the power apparatus to reduce their insulation levels and manufacturing bottleneck. The arrester for the 1000-kV ultra-high voltage ac power transmission system is designed as tank-type structure. The field-circuit combination numerical method combining the three-dimensional finite element method with circuit is proposed to analyze the potential distribution of GIS arrester. By comparing several design schemes, the most effective method to improve the potential distribution along the varistor column is to increase the voltage gradient of the ZnO varistor. Synthesizing several influential factors, the suitable voltage gradient of ZnO varistor should be controlled to 435 V/mm, and the resulted nonuniform degree of the potential distribution along the varistor column inside the GIS arrester would be controlled smaller than 10%. The result in this paper provides the fundamental technical index for the study of the high voltage gradient ZnO varistors.
基金Project(50871044)supported by the National Natural Science Foundation of ChinaProject(2012M511207)supported by the Postdoctoral Science Foundation of ChinaProject(10122011)supported by the Science Research Foundation of Wuhan Institute Technology,China
文摘Effect of direct current electric field （DCEF） on corrosion behaviour of copper printed circuit board （PCB-Cu）, Cl-ion migration behaviour, dendrites growth under thin electrolyte layer was investigated using potentiodynamic polarization and scanning electron microscopy （SEM） with energy dispersive spectrometer （EDS）. Results indicate that DCEF decreases the corrosion of PCB-Cu;Cl-ions directionally migrate from the negative pole to the positive pole, and enrich on the surface of the positive pole, which causes serious localized corrosion; dendrites grow on the surface of the negative pole, and the rate and scale of dendrite growth become faster and greater with the increase of external voltage and exposure time, respectively.
基金the National Natural Science Foundation of China(Nos.51991340,51991341,51802090,and 61874041)from the Hunan Science Fund for Excellent Young Scholars(No.812019037).
文摘Metal-oxide-semiconductor field effect transistors(MOSFET)based on two-dimensional(2D)semiconductors have attracted extensive attention owing to their excellent transport properties,atomically thin geometry,and tunable bandgaps.Besides improving the transistor performance of individual device,lots of efforts have been devoted to achieving 2D logic functions or integrated circuit towards practical application.In this review,we discussed the recent progresses of 2D-based logic circuit.We will first start with the different methods for realization of n-type metal-oxide-semiconductor(NMOS)-only(or p-type metal-oxide-semiconductor(PMOS)-only)logic circuit.Next,various device polarity control and complementary-metal-oxide-semiconductor(CMOS)approaches are summarized,including utilizing different 2D semiconductors with intrinsic complementary doping,charge transfer doping,contact engineering,and electrostatics doping.We will discuss the merits and drawbacks of each approach,and lastly conclude with a short perspective on the challenges and future developments of 2D logic circuit.
基金supported in part by the National High Technology Research and Development Program of China (863 Program)(2006AA12A108)CSC International Scholarship (2008104769)
文摘With research on the carrier phase synchronization and symbol synchronization algorithm of demodulation module, a synchronization circuit system is designed for GPS software receiver based on field programmable gate array （FPGA）, and a series of experiment is done on the hardware platform. The result shows the all-digital synchronization and demodulation of GPS intermediate frequency （IF） signal can be realized and applied in embedded real-time GPS software receiver system. It is verified that the decision-directed joint tracking algorithm of carrier phase and symbol timing for received signals from GPS is reasonable. In addition, the loop works steadily and can be used for receiving GPS signals using synchronous demodulation. The synchronization circuit for GPS software receiver designed based on FPGA has the features of low cost, miniaturization, low power and real-time. Surely, it will become one of the development directions for GPS and even GNSS embedded real-time software receiver.
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.
文摘The electric field intensity (EFI) is important characteristic quantity for evaluating the internal insulation state of cable joints. Based on finite element method, this paper proposes two EFI research methods, field-circuit coupling method and equivalent circuit method. The average EFI of the inner surface of the outer semi-conducting shield can be calculated from the current in the measuring circuit. The relative error between these two methods is about 15%, which roughly proves the consistency of the two methods. Further practical application research enables online monitoring of cable joints.
基金Project supported by the National Natural Science Foundation of China(Grant No.61073049)the Shanghai Leading Academic Discipline Project(Grant No.J50103)the Doctorate Foundation of Education Ministry of China(Grant No.20093108110016)
文摘Reconfiguration is the key to produce an applicable ternary optical computer （TOC）. The method to implement the reconfiguration function determines whether a TOC can step into applied fields or not. In this work, a design of the reconfiguration circuit based on field programmable gates array （FPGA） is proposed, and the structure of the entire hardware system is discussed.
