- 标题
- 摘要
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- 实验方案
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Effects of waveform parameters on the breakdown characteristics of OIP subjected to impulse voltages and evaluation method for waveform equivalence
摘要： The impulse voltage wave invading a transformer is not the double exponential impulse wave (DEIW) specified by the IEC but a non-standard waveform with oscillation attenuation characteristics, and this fact leads to doubts about the scientificity and optimality of insulation coordination. A key solution for this issue is the establishment of an equivalent relationship between the measured non-standard impulse voltage wave and the DEIW. In this study, a test platform of multiparameter impulse voltage was set up. Then, the authors obtained the 50% breakdown voltage (U50%) of the oil-impregnated paper (OIP) for transformer under the bipolar oscillatory attenuated impulse wave (BOAIW) and the DEIW with different waveform parameters. The effects of waveform parameters on the breakdown characteristics of the OIP were finally revealed. On the basis of experimental data and several mathematical methods, the authors established the U50% prediction mathematical models for the OIP under the BOAIW and DEIW. Based on the prediction models and the microfluctuation characteristics of measured overvoltage's waveform parameters, the authors proposed a method for evaluating the waveform equivalence. The characteristics of voltage amplitude and change rate were regarded as the two key factors for the waveform equivalence of this method.
关键词： evaluation method,breakdown characteristics,waveform equivalence,impulse voltage,oil-impregnated paper
更新于2025-09-23 15:21:21
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Gate Conduction Mechanisms and Lifetime Modeling of p-Gate AlGaN/GaN High-Electron-Mobility Transistors
摘要： The gate conduction mechanisms in p-gallium nitride (GaN)/AlGaN/GaN enhancement mode transistors are investigated using temperature-dependent dc gate current measurements. In each of the different gate voltage regions, a physical model is proposed and compared to experiment. At negative gate bias, Poole–Frenkel emission (PFE) occurs within the passivation dielectric from gate to source. At positive gate bias, the p-GaN/AlGaN/GaN “p-i-n” diode is in forward operation mode, and the gate current is limited by hole supply at the Schottky contact. At low gate voltages, the current is governed by thermionic emission with Schottky barrier lowering in dislocation lines. Increasing the gate voltage and temperature results in thermally assisted tunneling (TAT) across the same barrier. An improved gate process reduces the gate current in the positive gate bias region and eliminates the onset of TAT. However, at high positive gate bias, a sharp increase in current is observed originating from PFE at the metal/p-GaN interface. Using the extracted conduction mechanisms for both devices, accurate lifetime models are constructed. The device fabricated with the novel gate process exhibits a maximum gate voltage of 7.2 V at t1% = 10 years.
关键词： time-dependent breakdown (TDB),p-GaN gate,high-electron-mobility transistor (HEMT),enhancement mode,gallium nitride (GaN),Conduction mechanism
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Arrays of Si Field Emitter Individually Regulated by Si Nanowires High Breakdown Voltages and Enhanced Performance
摘要： We fabricate Si field emitter arrays (FEAs) with integrated Si nanowire current limiters and investigate a method to enable higher voltage operation, which can potentially increase achievable current densities. In this work, we focus on the dielectric breakdown occurring in the vicinity of the nanopillar. A deeper etch is shown to increase the breakdown voltage but at the expense of poorer field emission characteristics possibly due to the loss of mechanical support or increased surface states.
关键词： field emitter arrays,Silicon,breakdown voltage,current limiters
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Activation of carbon nanotube film by gas discharge breakdown
摘要： Carbon nanotubes (CNTs) is considered to be eminently suitable cold-cathode material. We found that exposure of CNT films to gas discharge breakdown generated in atmospheric argon gas causes significant morphology changes, which show many dispersed CNTs, on those surfaces. These indicate that the exposure of the CNT film to the gas discharge breakdown can be used as a method for improvement of the field emission property of the CNT film. In this study, field emission properties of the CNT film that was exposed to the gas discharge breakdown was investigated. Many crater-shaped holes whose circumferences were surrounded by many dispersed CNTs were found after the exposure of the CNT film to the discharge breakdown. We found that the CNT film after the exposure of the gas discharge breakdown gave better field emission properties than it before the exposure.
关键词： carbon nanotubes,field emission,gas discharge breakdown,spark discharge
更新于2025-09-23 15:21:21
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[IEEE 2018 3rd International Conference On Internet of Things: Smart Innovation and Usages (IoT-SIU) - Bhimtal, India (2018.2.23-2018.2.24)] 2018 3rd International Conference On Internet of Things: Smart Innovation and Usages (IoT-SIU) - A 100 V Lateral Trench Power MOSFET on InGaAs/InP
摘要： In this paper, we present a lateral-trench metal-oxide-semiconductor field-effect transistor (LT-MOSFET) on high mobility InGaAs material. The proposed LT-MOSFET emerged with trench technology consist a gate electrode placed vertically in a trench on the left end of the p-body region. The trench in the drift region introduce a RESURF effect to reduces the electric field and improves the device breakdown voltage. By 2-D numerical simulation, LT-MOSFET exhibits 2.4 times improvement on breakdown voltage with 3.3 times high figure-of-merit in comparison with the conventional-lateral MOSFET (CLMOSFET) for identical cell pitch and gate length.
关键词： figure of merit,breakdown voltage,lateral-trench,InGaAs
更新于2025-09-23 15:21:21
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The effects of cathode electrodeposited polymer film on the long vacuum gap breakdown
摘要： Vacuum surface discharge is one of the most important issues for vacuum insulation. In this paper, a method for breakdown ?eld strength enhancement of long vacuum gap is put forward, through depositing polymer dielectric coating on the electrode surface. The physical mechanism that the polymer ?lm changes the electrode surface state is analyzed. After a layer of polymer ?lm is deposited on the electrode surface, the decreased surface ?eld strength and improved micro-surface state both help to suppress the ?eld electron emission from the cathode. The technique of cathode electrodeposition for high polymers such as epoxy resin (ER), epoxy acrylate (EA), polyimide (PI) and poly(ether-ether-ketone) (PEEK) was explored, and the thickness of the electrodeposited coating can reach 20–50 mm. The effects of the electrodeposited polymer coatings of electrodes on the 2.5 cm vacuum gap breakdown were studied under a high-voltage vacuum experiment platform. Experimental results showed that when ER, EA and PEEK coatings with thickness of 25–45 mm were respectively electrodeposited on the 95 cm2 plate cathode, the initial-breakdown ?eld strengths of the 2.5 cm vacuum gap were enhanced by 20.7%–22.4%. The enhancement of the initial-breakdown ?eld strength was restricted by the coating defects, grain boundary defects on the cathode surface, and the micro-triple-point emission after the fusing of some local coating points due to the electron bombardments.
关键词： vacuum gap breakdown,vacuum insulation,cathode electrodeposition,polymer dielectric coating,field electron emission
更新于2025-09-23 15:21:21
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Identification of Gravesa?? ophthalmology by laser-induced breakdown spectroscopy combined with machine learning method
摘要： Diagnosis of the Graves’ ophthalmology remains a significant challenge. We identified between Graves’ ophthalmology tissues and healthy controls by using laser-induced breakdown spectroscopy (LIBS) combined with machine learning method. In this work, the paraffin-embedded samples of the Graves’ ophthalmology were prepared for LIBS spectra acquisition. The metallic elements (Na, K, Al, Ca), non-metallic element (O) and molecular bands ((C-N), (C-O)) were selected for diagnosing Graves’ ophthalmology. The selected spectral lines were inputted into the supervised classification methods including linear discriminant analysis (LDA), support vector machine (SVM), k-nearest neighbor (kNN), and generalized regression neural network (GRNN), respectively. The results showed that the predicted accuracy rates of LDA, SVM, kNN, GRNN were 76.33%, 96.28%, 96.56%, and 96.33%, respectively. The sensitivity of four models were 75.89%, 93.78%, 96.78%, and 96.67%, respectively. The specificity of four models were 76.78%, 98.78%, 96.33%, and 96.00%, respectively. This demonstrated that LIBS assisted with a nonlinear model can be used to identify Graves’ ophthalmopathy with a higher rate of accuracy. The kNN had the best performance by comparing the three nonlinear models. Therefore, LIBS combined with machine learning method can be an effective way to discriminate Graves’ ophthalmology.
关键词： support vector machine (SVM),linear discriminant analysis (LDA),Graves’ ophthalmology,laser-induced breakdown spectroscopy (LIBS),k-nearest neighbor (kNN),generalized regression neural network (GRNN)
更新于2025-09-23 15:21:01
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Robust flower-like ZnO assembled ?2-PVDF/BT hybrid nanocomposite: Excellent energy harvester
摘要： Need of renewable green energy sources due to low cost synthesis, mechanically strong, high energy storage capacity with improved dielectric performance have been receiving much attention. Present work render the ZnO particle and flower-like morphology assemble semicrystalline β phase PVDF/BT nanocomposite, successfully synthesized by spin coating method and characterized by XRD, SEM, EDS and FTIR techniques. Also the energy storage density of composite with modified structure is largely increased with value 0.056 Jcm-3 at 6 MV/m which is 66% higher than virgin β-PVDF and 82% piezoelectric energy harvesting efficiency. Maximum dielectric constant is 1774 at 1 Hz for PVDF-BaTiO3-ZnOf [P-BT-ZnOf] nanocomposite film and maximum breakdown strength of 43 kVcm-1. Electrochemical study reveals that P-BT-ZnOf nanocomposite film manifest better potential material. In terms of mechanical performance, P-BT-ZnOf nanocomposite shows maximum Young modulus of 204 MPa, tensile strength of 28.7 MPa and 23.1% elongation to break. These results provide promising capability to enhance the performance of composites for energy storage application, transducers, sensors, capacitors etc.
关键词： Energy density,Tensile strength,Dielectric constant,Nanocomposites,Breakdown strength
更新于2025-09-23 15:21:01
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Temporal and spatial evolution measurement of laser-induced breakdown spectroscopy on hydrogen retention in tantalum
摘要： Temporal and spatial evolution measurement of laser-induced breakdown spectroscopy on hydrogen retention in tantalum. Fuel retention measurement on plasma-facing components (PFCs) is an active field of study in magnetic confinement nuclear fusion devices. Laser-induced breakdown spectroscopy (LIBS) diagnostic method has been well demonstrated to detect the elemental distribution in PFCs. In this work, an upgraded co-axis LIBS system based on the linear fibers bundle collection system has been developed to measure the hydrogen (H) retention on tantalum (Ta) sample under the vacuum condition. The spatial resolution measurement on the different positions of the LIBS plasma can be achieved simultaneously with the various delay time. The temporal and spatial evolution of LIBS plasma and optimize the current collection system of the in situ LIBS in fusion devices.
关键词： tokamak,fuel retention,temporal and spatial evolution,laser-induced breakdown spectroscopy
更新于2025-09-23 15:21:01
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Detection of Nutrition and Toxic Elements in Pakistani Pepper Powders Using Laser Induced Breakdown Spectroscopy
摘要： In the current paper, we applied laser induced breakdown spectroscopy (LIBS) to determine the elemental distribution of nutritional and trace heavy metals in pepper powders available in Pakistan using standard calibration curve laser induced breakdown spectroscopy (CC-LIBS) technique. The samples were found to contained elements like K, Ca, Mg, Na, Fe, Zn, Al, Pb, Cu, and Cr. Additionally, we also identified the atmospheric H-alpha line of hydrogen in the spectra which was used to estimate the electron number density. To achieve a highly sensitive LIBS system to determine nutritional and trace amounts of toxic metals in pepper powders and to achieve the best limit of detection, the LIBS system was optimized by studying the dependency of LIBS signal intensity on laser irradiance, variation in spacing between the focusing lens and target as well on the gate width. To justify the results of LIBS study, we also determined the concentration of alike (duplicate) peppers by digesting samples in appropriate solvents using a standard method like inductively coupled plasma-optical emission spectrometry (ICP-OES). The minimum detection limit was recognized for trace heavy metals from calibration curves. The results of LIBS displayed noteworthy conformity with those acquired from the ICP-OES analysis. Results of both the techniques clearly revealed that K was the most abundant element in all the peppers followed by Ca, Mg, Na, Fe, Al, Pb, Zn, Cu, and Cr. The relative accuracy of our LIBS system for different species as compared with ICP technique was in the range of 0.08–0.3 at 2.5 % error confidence. Conclusively, the present work demonstrated the suitability of LIBS technique due to its rapid, non destructive and eco-friendly approach for food security.
关键词： ICP-OES,detection of heavy metals,peppers analysis,laser induced breakdown spectroscopy,plasma parameters,Health impacts of toxic metals,laser applications
更新于2025-09-23 15:21:01