scholarly journals Численное моделирование субнаносекундного лавинного переключения кремниевых n-=SUP=-+-=/SUP=--n-n-=SUP=-+-=/SUP=--структур

2019 ◽  
Vol 53 (3) ◽  
pp. 401
Author(s):  
Н.И. Подольская ◽  
П.Б. Родин
Keyword(s):  
Electric Field ◽  
Field Distribution ◽  
Voltage Pulse ◽  
Transverse Direction ◽  
Current Flow ◽  
Impact Ionization ◽  
Switching Time ◽  
Flow Direction ◽  
Initial Voltage ◽  
Simulation Results

AbstractThe simulations of recently discovered effect of subnanosecond avalanche switching of Si n ^+− n − n ^+-structures have been performed. The electric field in n ^+− n − n ^+-structure is shown to remain quasi-uniform along the current flow direction during the voltage rise stage and it reaches the effective threshold of impact ionization of ~200 kV/cm in the whole n-base. Comparing simulation results with experiments we argue that the field distribution is as well uniform in the transverse direction. Hense, the ultrafast avalanche transient develops quasi-uniformly in the whole n-base volume. The switching time is about ~150 ps. We compare numerical results obtained for various impact ionization models and estimate parameters of the initial voltage pulse that are required for ultrafast avalanche switching of n ^+− n − n ^+-structures.

scholarly journals Rapid AC Electrokinetic Micromixer with Electrically Conductive Sidewalls

Micromachines ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 34
Author(s):  
Fang Yang ◽  
Wei Zhao ◽  
Cuifang Kuang ◽  
Guiren Wang
Keyword(s):  
Electric Field ◽  
Transverse Direction ◽  
Flow Direction ◽  
Conductivity Ratio ◽  
Mixing Length ◽  
Electrically Conductive ◽  
Electrokinetic Phenomena ◽  
Two Fluids ◽  
Conductivity Gradient ◽  
Lower Voltage

We report a quasi T-channel electrokinetics-based micromixer with electrically conductive sidewalls, where the electric field is in the transverse direction of the flow and parallel to the conductivity gradient at the interface between two fluids to be mixed. Mixing results are first compared with another widely studied micromixer configuration, where electrodes are located at the inlet and outlet of the channel with electric field parallel to bulk flow direction but orthogonal to the conductivity gradient at the interface between the two fluids to be mixed. Faster mixing is achieved in the micromixer with conductive sidewalls. Effects of Re numbers, applied AC voltage and frequency, and conductivity ratio of the two fluids to be mixed on mixing results were investigated. The results reveal that the mixing length becomes shorter with low Re number and mixing with increased voltage and decreased frequency. Higher conductivity ratio leads to stronger mixing result. It was also found that, under low conductivity ratio, compared with the case where electrodes are located at the end of the channel, the conductive sidewalls can generate fast mixing at much lower voltage, higher frequency, and lower conductivity ratio. The study of this micromixer could broaden our understanding of electrokinetic phenomena and provide new tools for sample preparation in applications such as organ-on-a-chip where fast mixing is required.

scholarly journals Numerical Investigation of Nanostructure Orientation on Electroosmotic Flow

Micromachines ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 971
Author(s):  
An Eng Lim ◽  
Yee Cheong Lam
Keyword(s):  
Electric Field ◽  
Field Distribution ◽  
Applied Electric Field ◽  
Electroosmotic Flow ◽  
Electric Field Distribution ◽  
Flow Direction ◽  
Fluid Velocity ◽  
Orientation Angle ◽  
Dependent Behavior ◽  
Velocity Region

Electroosmotic flow (EOF) is fluid flow induced by an applied electric field, which has been widely employed in various micro-/nanofluidic applications. Past investigations have revealed that the presence of nanostructures in microchannel reduces EOF. Hitherto, the angle-dependent behavior of nanoline structures on EOF has not yet been studied in detail and its understanding is lacking. Numerical analyses of the effect of nanoline orientation angle θ on EOF to reveal the associated mechanisms were conducted in this investigation. When θ increases from 5° to 90° (from parallel to perpendicular to the flow direction), the average EOF velocity decreases exponentially due to the increase in distortion of the applied electric field distribution at the structured surface, as a result of the increased apparent nanolines per unit microchannel length. With increasing nanoline width W, the decrease of average EOF velocity is fairly linear, attributed to the simultaneous narrowing of nanoline ridge (high local fluid velocity region). While increasing nanoline depth D results in a monotonic decrease of the average EOF velocity. This reduction stabilizes for aspect ratio D/W > 0.5 as the electric field distribution distortion within the nanoline trench remains nearly constant. This investigation reveals that the effects on EOF of nanolines, and by extrapolation for any nanostructures, may be directly attributed to their effects on the distortion of the applied electric field distribution within a microchannel.

scholarly journals A Review about the Modeling and Simulation of Electro-Quasistatic Fields in HVDC Cable Systems

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5189
Author(s):  
Christoph Jörgens ◽  
Markus Clemens
Keyword(s):  
Electric Field ◽  
Field Distribution ◽  
High Voltage ◽  
Electric Field Distribution ◽  
Computation Time ◽  
Charge Movement ◽  
Time Varying ◽  
Long Distance ◽  
Cable Systems ◽  
Simulation Results

In comparison to high-voltage alternating current (HVAC) cable systems, high-voltage direct current (HVDC) systems have several advantages, e.g., the transmitted power or long-distance transmission. The insulating materials feature a non-linear dependency on the electric field and the temperature. Applying a constant voltage, space charges accumulate in the insulation and yield a slowly time-varying electric field. As a complement to measurements, numerical simulations are used to obtain the electric field distribution inside the insulation. The simulation results can be used to design HVDC cable components such that possible failure can be avoided. This work is a review about the simulation of the time-varying electric field in HVDC cable components, using conductivity-based cable models. The effective mechanisms and descriptions of charge movement result in different conductivity models. The corresponding simulation results of the models are compared against measurements and analytic approximations. Different numerical techniques show variations of the accuracy and the computation time that are compared. Coupled electro-thermal field simulations are applied to consider the environment and its effect on the resulting electric field distribution. A special case of an electro-quasistatic field describes the drying process of soil, resulting from the temperature and electric field. The effect of electro-osmosis at HVDC ground electrodes is considered within this model.

scholarly journals FINITE ELEMENT MODELLING FOR ELECTRIC FIELD DISTRIBUTION AROUND POSITIVE STREAMERS IN OIL

2020 ◽  
Vol 58 (1) ◽  
pp. 56
Author(s):  
Dung Van Nguyen
Keyword(s):  
Finite Element ◽  
Electric Field ◽  
Field Distribution ◽  
Electric Field Distribution ◽  
Spherical Model ◽  
Shielding Effect ◽  
Geometrical Shape ◽  
Multiphysics Modelling ◽  
Positive Streamers ◽  
Simulation Results

Electric field distribution of positive streamers during propagation was determined with the finite element method by using COMSOL multiphysics. Modelling was performed at 210 kV and 270 kV. The geometrical shape of streamers was modelled with cylinder and sphere for the case of 210 kV while a growing cylinder was used for streamer propagation at 270 kV. In addition, a spherical model was used for determining the correlation between streamer branching and the electric field. It is obtained from the simulation results that the 2nd mode streamers has the electric field at channel tips of about 0.1 MV/cm while 8.3 MV/cm was received for the 4th mode streamers. The simulation results also reveal that the shielding effect resulting from streamer branching significantly reduces the electric field at the channel tips, and the shielding effect disappears with the angle a between channels is about 30o-60o depending on the size of streamer envelope. The hypothesis on correlation among velocity, streamer branching and electric field is suggested.

Electric Field Simulation of Typical Defects in the Epoxy/Paper Composites Insulated Tubular Bus

2018 ◽  
Vol 922 ◽  
pp. 157-162 ◽  
Author(s):  
Cheng Lei Li ◽  
Rui Liu ◽  
Peng Hu Li ◽  
Wen Pei Li ◽  
Nai Kui Gao
Keyword(s):  
Electric Field ◽  
Field Distribution ◽  
Electric Field Distribution ◽  
Three Dimensional ◽  
Conducting Layer ◽  
Static Electric Field ◽  
Three Dimensional Model ◽  
Actual Structure ◽  
Simulation Results ◽  
Air Void

Many failures had occurred in operation of insulated tubular bus because of the poor product quality, and its primary reason was that some defects were led into the insulation system in the production, then the local electric field would increase and then result in partial discharge, which could accelerate the aging and even breakdown of the materials. In this research, a 1/4 three-dimensional model was established according to the actual structure of insulated tubular bus, and the simulation results obtained from static electric field and quasi-static electric field were compared. Besides, the electric field distribution of insulated tubular bus with typical defects was simulated based on ANSYS software. These three defects were air void, moisture and damage of semi-conducting layer. The simulation results showed that the electric field distribution of insulated tubular bus with typical defects was more suitable with quasi-static electric field simulating. The maximum electric field value was different with different defects, and dependent on the location and size of defects.

Analysis of Electric Field Homogenization of Converter Transformer Barrier System Based on Nano Modification of Pressboard

2014 ◽  
Vol 981 ◽  
pp. 940-945 ◽  
Author(s):  
Qing Guo Chen ◽  
He Qian Liu ◽  
Xiang Li Zhuge ◽  
Ming He Chi ◽  
Xin Lao Wei
Keyword(s):  
Silicon Carbide ◽  
Electric Field ◽  
Field Distribution ◽  
Electric Field Distribution ◽  
Transformer Oil ◽  
Uniform Electric Field ◽  
Nonlinear Characteristic ◽  
Nonlinear Conductivity ◽  
Simulation Results ◽  
Doping Ratio

In order to solve the problem of non-uniform electric field distribution in converter transformer barrier system caused by conductivity difference between the transformer oil and pressboard, the SiC(silicon carbide) modified pressboard was developed by nano doping method. The conductivity of modified pressboard was measured. The measuring results show that the conductivity of modified pressboard increases exponentially with the increase of nano SiC doping ratio. The electric field strength has obvious influence on conductivity at high nano doping ratio, which shows great nonlinear characteristic. Based on the nonlinear conductivity characteristic of modified pressboard, the homogenizing effect of the nano modified pressboard on electric field distribution was verified by simulation. The simulation results show that the electric field distribution under DC and polarity reversal voltage in barrier system can be well homogenized by using the nonlinear characteristic of nano modified pressboard.

Improvement of On-Resistance Degradation Induced by Hot Carrier Injection in SOI-LDMOS

2015 ◽  
Vol 764-765 ◽  
pp. 521-525
Author(s):  
Vivek Ningaraju ◽  
Shao Ming Yang ◽  
Gene Sheu ◽  
Mohammad Amanullah ◽  
Erry Dwi Kurniawan ◽  
...  
Keyword(s):  
Electric Field ◽  
Breakdown Voltage ◽  
Current Flow ◽  
Impact Ionization ◽  
Carrier Injection ◽  
Hot Carrier ◽  
Hot Carrier Injection ◽  
Drain Side ◽  
Field Oxide ◽  
State Resistance

This paper presents how to improve specific o n-state resistance (Ron) induced by the HCI of a SOI LDMOS device. In manufacturing of UHV device, trade-off between on state resistance and breakdown voltage is always present. But with our process design we are able to improve Ron degradation without compromising the-breakdown voltage. In our design the peak electric field is under gate near source side, due to low electric field near drain helps to increase the current flow much better hence it helps to improve Ron and Vth. If the peak field is located near drain side, the hot holes is easy to penetrate to field oxide and avoid current flow then it causes increase in the Ron.Our simulation results shows 0.27% and 0.95% Ron and Vth increases respectively even at 1e5 second stress time .The Ron degradation phenomenon was analyzed with the 2-D simulation of electric field and impact ionization generation.

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