Electric Field Model Research Articles

Analysis of the explanations of pre-service physics teachers about the Faraday Cage Effect and the Pointed Conductor Effect

We study the evolution of the explanations made by a group of pre-service physics teachers when experiencing with two different electrostatic phenomena: the Faraday Cage Effect and the Pointed Conductor Effect. By using a teaching and learning sequence (TLS) to help students improve their understanding about these two electrostatic effects, we find that these explanations improve when teachers are able to combine correctly the electric-field model with the charge-distribution model.

Nonlinear free and forced vibration of porous piezoelectric doubly-curved shells based on NUEF model

In this paper, the nonlinear free and forced vibration of porous piezoelectric doubly-curved shells resting on visco-Pasternak foundation is performed within the framework of the nonuniform electric field (NUEF) model and von Kármán geometric nonlinearity assumption. Three types of porosity distribution are adopted to study the effect of porosity on the nonlinear dynamic responses of the current system. According to Hamilton’s principle, the nonlinear governing differential equations are obtained. For the nonlinear free vibration of porous piezoelectric doubly-curved shells, an analytical solution is achieved by utilizing the harmonic balance method. For the nonlinear forced vibration of the present system, the numerical solution is obtained by means of Runge–Kutta method. Through numerical examples, the relationship between nonlinear free vibration responses and nonlinear forced vibration responses is explored under different amplitudes of external excitation, width to thickness ratios, types of porosity distribution, electric field models and elastic foundation parameters. The main novelty of the present study is that the nonlinear frequency ratio that is calculated based on the nonlinear free vibration, is in excellent agreement with the resonant frequency ratio which is determined on the basis of the nonlinear forced vibration.

Research on modularizing design of 10 kV switchgear with line outlet for live maintenance

In order to improve the reliability and safety of power supply and reduce the failure rate of switchgear, this paper designs a novel high-voltage switchgear which is reliable and safe. A simulation model for electric field and temperature field simulation is established to check the insulation and temperature rise performance of the new designing switchgear. The electric field simulation results show that the place where there has connection or corner has strong chance to occur partial discharge. The heat field results reveal that even in the condition of passing through current with long operation time, the maximum temperature rise of the switchgear is 55.9 K and 48.7 K respectively, which is lower than the standard design requirement 70 K. Some measures can be taken to improve the insulation and temperature rise performance of the new switchgear, such as polishing the connection or using stainless steel at the top of the switchgear.

Simulation and analysis of through-mask electrochemical machining with moving tools

At present, the development of through-mask micro-electrochemical machining is only limited to static machining, where the size of the tool is usually the same as that of the workpiece. However, in the electrochemical processing, metal with good electrical conductivity is chosen as the tool electrode, and it is usually very expensive. Based on the cost consideration, a moving tool with small size may be preferred. Finite element method is used in this paper to create the electric field model of through-mask micro-electrochemical machining with moving tool. The effects of the parameters, such as applied voltage, mask thickness, on the machining shape are investigated. The results show that the higher the applied voltage, the larger the machining depth and width, and also the better the aspect ratio. When the thickness of the mask is thin, the electric field is unevenly distributed and the lateral corrosion is more serious. There is an island-like phenomenon, which is related to the masking of the mask. When the moving speed is relatively slow, the relative processing time is longer. The current density accumulated on the surface of the workpiece is thus higher and the material removal rate is higher. As the processing time increases, the machining depth becomes deeper, and the forward corrosion rate is slow down.

Research on Machining Gap Distribution in Wire Electrochemical Micromachining

Wire electrochemical micromachining (WECMM) has become a research hotspot in recent years due to its advantages in machining metallic microstructures. Profiles of metallic microstructures fabricated by WECMM are determined by the machining gap distribution. This paper focuses on equilibrium machining gap distribution in WECMM. A two-dimensional electric field model of WECMM was established and the evolution process of slit profile was investigated. It was found that in machining equilibrium status, the machining gap gets the minimum value at the wire electrode feeding direction and exponentially increases with the increase of the induced angle between the wire electrode normal direction and its feeding direction. Furthermore, the effects of wire electrode diameter, machining voltage, and wire electrode feed rate on the equilibrium machining gap distribution were studied through machining simulation. The quantitative relationship among the machining gap at any wire electrode normal direction, the machining voltage, and the wire electrode feed rate was determined through function fitting. Finally, machining experiments were carried out to verify the regularity of the machining gap distribution. Experimental results are basically consistent with the simulation and function fitting results, with the ratio of the calculation error to the experimental value less than 12.78%.

Systems Theory: Simulation Analysis of Space Charge Generation Mechanisms in Transformer Oil under High Electric Field

Simulation analysis plays an important role in Systems Theory nowadays. In order to reveal the mechanism of space charge injection and generation in the process of liquid dielectric breakdown, the discharge of transformer oil between needle-plane electrodes under high electric field is studied. Based on the 2-D hydrodynamic model and Poisson equation of electric field, the system simulation model of oil discharge by different charge generation mechanism is established, based on which the inception and propagation process of discharge is simulated by COMSOL. By system simulation, the temporal and spatial distribution of the electric field intensity, space charge density, electric potential and temperature of transformer oil is obtained and deeply analyzed. The simulation results prove that the space charge generated by metal field emission and ionic disassociation are neither of the major factor for streamer formation in transformer oil, while the Zener molecular ionization and impact ionization are the major factors. Our research improves the understanding of the inception, propagation and breakdown process for discharge in transformer oil, and also the ionization mechanism in the liquid dielectric

Multiplexed electrospray emission on a porous wedge

Linear porous wedge electrospray emitters exhibit a discrete number of emission sites that naturally form during operation. An analytical model is developed to examine the behavior and spacing of these emission sites via the pressure variation in the porous fluid flow associated with the flow focusing on each emission site, which is coupled with the local electric field. The solution for site spacing and current is informed by empirical results with support from electric field modeling and investigation of porous media parameters. Emission site currents of up to 500 nA and site spacings of roughly 50 µm–300 µm are predicted. Results from the model match well with experimental trends and provide further insights into the current and spacing of the discrete emission sites. These insights include the following: (1) for the investigated geometry, the total current can be estimated without taking into account the effects local to each emission site, (2) the wedge hydraulic resistance shows how the emitter output scales with emitter geometry and propellant properties, and (3) the emitted charge to mass ratio increases with the applied electric field. Last, we present a physical description of how specific charge increases with the restorative pressure from the reservoir.

Charging and Discharging Current Measurements and Impact of Polarization Dynamics on Electric Field Modeling in HVDC Paper-Insulated Cables

Accurate modeling and simulation of electric field transients in HVDC cables is an important support to optimize insulation system design and to evaluate the influence of voltage transients and steady-state conditions on accelerated ageing mechanisms and insulation reliability. Traditionally, field models considering time-independent permittivity and conductivity are used, but this approach neglects polarization mechanisms and charge trapping-detrapping phenomena. This article includes polarization dynamics in the field model and shows that its impact on transient electric field simulations in HVDC paper-insulated cables can be significant. A method is presented to infer the model parameters from experimental polarization and depolarization current measurements.

Statements of the boundary value problems in mathematical simulation of a quasistationary electric field in the atmosphere and ionosphere

Boundary-value problems which have to be solved in the frame of the mathematical models of quasi-stationary electric fields and currents in the global conductor, that consists of the Earth’s ionosphere and the atmosphere are formulated. The approach based on the domain decomposition is used. A quadratic energy functional is constructed. It allows us to reduce the solution of the boundary value problem for a three-dimensional elliptic differential equation with asymmetric coefficients to minimizing of the functional. Estimates of the quadratic form in comparison with the Dirichlet principle for the Poisson equation are obtained. These estimates allow us to assess the condition number of the matrix of the system of linear algebraic equations, arising in the numerical solution to the problem.

Mathematical Modelling of Electric and Magnetic Fields of Main Pipelines Cathodic Protection in Electrically Anisotropic Media

A mathematical model is constructed and computational experiments are performed to study the effect of anisotropy of the specific electrical conductivity of the soil on the distribution of electric and magnetic fields generated by cathodic electrochemical corrosion protection stations of the underground main pipeline (MP). The variation of electric and magnetic fields depending on the azimuth angle of rotation of the specific electrical conductivity tensor of the soil containing the pipeline is analysed.

Research on the Working Mechanism of Melt Metallurgical Effect

This paper takes rectangular tinned silver flake as the research object to explore the working mechanism of melt metallurgical effect. Firstly, the paper designs and processes rectangular tinned silver flake through the electroplating technology, then conducts low-overload pre-arc experiment with the metallurgical samples. According to the experiment results, it is proposed that “Under low overload current, the formation of silver-tin alloy leads to the increase of current density of the metallic silver layer, which significantly advances the break time of the silver flake. At the same time, the silver-tin interpenetration speed is a linear function of the temperature.” Finally, the self-programming software is used to establish the transient electric heating field model of the metallurgical tinned silver flake. By comparing simulation and experiment, the results verify the accuracy of the hypothesis, and obtain the working mechanism of the melt metallurgical effect, which provides a reliable theoretical basis for the design and application of the metallurgical trigger.

Mathematical modeling of electric fields in electrolysis technologies

Mathematical modeling of electric fields in electrolysis technologies

Reliability Analysis of A Novel On-line Maintenance Switchgear Under Transient Impulse

To improve the efficiency of switchgear maintenance, a double-action switchgear is presented to realize the purpose of on-line maintenance in this paper. And to check the reliability and safety of the novel design, a research about the insulation performance of the new design switchgear under two different impulse action is carried out. The two different impulse phenomena refer the switching process of the double-action switchgear and the lighting impulse respectively. The switchgear conversion equivalent circuit is established to analyze the transient process of the switching and the mechanism of lightning surge strike on the switchgear is analyzed as well. Based on these, an 3D electric field model is established to calculate the distribution of electric field under switchgear transient condition and the lightning impulse condition respectively. The results show that when the new switchgear operates under the condition of the maximum overvoltage during the switching progress, the maximum field strength is 4.35×105V/m, which is less than the air breakdown field strength. Under the extreme conditions of lightning surge strike, the maximum field strength in the main switchgear and stand-by switchgear is 1.415×107V/m and 5.093×106V/m respectively, where the breakdown may occur. Lightning arresters is quite necessary to be adopted to protect the new switchgear.

Mathematical Model and Numerical Simulation for Electric Field Induced Cancer Cell Migration

A mathematical model describing the interaction of cancer cells with the urokinase plasminogen activation system is represented by a system of partial differential equations, in which cancer cell dynamics accounts for diffusion, chemotaxis, and haptotaxis contributions. The mutual relations between nerve fibers and tumors have been recently investigated, in particular, the role of nerves in the development of tumors, as well neurogenesis induced by cancer cells. Such mechanisms are mediated by neurotransmitters released by neurons as a consequence of electrical stimuli flowing along the nerves, and therefore electric fields can be present inside biological tissues, in particular, inside tumors. Considering cancer cells as negatively charged particles immersed in the correct biological environment and subjected to an external electric field, the effect of the latter on cancer cell dynamics is still unknown. Here, we implement a mathematical model that accounts for the interaction of cancer cells with the urokinase plasminogen activation system subjected to a uniform applied electric field, simulating the first stage of cancer cell dynamics in a three-dimensional axial symmetric domain. The obtained numerical results predict that cancer cells can be moved along a preferred direction by an applied electric field, suggesting new and interesting strategies in cancer therapy.

Formation of the Low‐Energy “Finger” Ion Spectral Structure Near the Inner Edge of the Plasma Sheet

AbstractWe present a case study of the H+, He+, and O+ low‐energy “finger” structure observed by the Van Allen Probe A Helium, Oxygen, Proton, and Electron (HOPE) spectrometer on 26 October 2016. This structure, whose characteristic energy is from approximately tens of eV to a few keV, looks like a “finger” that is rich in O+ and He+, faint in H+ on an energy‐time spectrogram. By using the Space Weather Modeling Framework (SWMF) and Weimer05 electric fields, combined with a dipole or more self‐consistent magnetohydrodynamic (MHD) magnetic field, backward tracing of O+ reveals that the structure is formed by ions with a long drift time from the plasma sheet during the magnetic storm main phase to the inner region with trajectories dominated by eastward drift motion, and the formation depends on the convection electric field model. The heavy ion dominance of the feature is explained by charge exchange losses along the long slow drift paths.

Measurement and Modeling of Both Distant and Close Electric Fields of an M‐Component in Rocket‐Triggered Lightning

AbstractSimultaneous measurements of current and multiple‐station electric fields associated with a 5.4‐kA‐peak M‐component in rocket‐triggered lightning are presented in this study. A close‐range electric field measurement site was located northeast of the triggering site, 195° clockwise from South, at a distance of 78 m, while the distant multiple stations in this study were located southwest of the lightning triggering site (25–48°, clockwise from South) at a distance ranging from 69 to 126 km. Both the fast microsecond‐scale and slow millisecond‐scale pulses were observed at six distant stations. At the close station, the fast pulse was not noticeable. The magnitude and half‐peak width of the fast pulse were in the range of 0.91–1.93 V/m and 2.0–3.0 μs, respectively. The corresponding parameters for the slow pulse were, respectively, in the range of 0.59–1.29 V/m and 20.0–25.1 μs. The time lag between the onset of the channel‐base current and the far electric field of the M‐component was 18 μs. This time lag was used to deduce the ratio of the M‐component channel length and the wave speed. The classical guided wave M‐component model proposed by Rakov et al. (1995,https://doi.org/10.1029/95JD01924) to simulate the slow, millisecond‐scale field pulse assumes that neither the incident nor the reflected current wave undergoes attenuation even though the wave propagation occurs along a lossy channel. A modified guided wave M‐component model is proposed in this study in which the M‐component current wave attenuates with an exponential decay. Based on the best agreement achieved between the simulated fields using the modified two‐wave M‐component model and the observed near and far electric fields, the channel length, the M‐component wave speed, and the current attenuation constant were inferred, respectively, as 1.8 km, 1 × 108 m/s, and 3 km. It is shown that the modified guided wave M‐component model is able to reproduce reasonably well the electric fields both at close and far distance ranges.

Optimisation of an in-process lineal dielectric sensor for liquid moulding of carbon fibre composites

A dielectric sensor appropriate for process monitoring of carbon fibre composites manufacturing has been optimised and implemented in Resin Transfer Moulding (RTM). The sensor comprises a pair of twisted insulated copper wires and can be adapted to monitor both flow and cure. To simulate the dielectric response of the sensor, an electric field model was developed. The model was coupled with a multi-objective optimisation genetic algorithm to optimise the sensor design. The optimisation showed that increasing wire radius and decreasing coating thickness increases sensor sensitivity. Different sensor designs were implemented and used in a series of RTM trials to validate the technology in industrial conditions. The selelcted sensors operated successfully at pressures up to 7 bar and temperatures up to 180 °C. A low diameter sensor using copper wire coated with polyimide showed the best response monitoring flow with an accuracy of 95%, whilst also following the cure and identifying vitrification.

Analytical model of electric field assisted ion diffusion into glass containing two indigenous mobile species, with application to poling

An analytical model of electric field assisted diffusion of ions into glass is extended to include two indigenous mobile ion species that are initially uniformly distributed within the glass. A quasi-stationary state solution that includes diffusion effects and is applicable when the invasive ions have a lower mobility than the two indigenous species is presented. It is relevant to the electrical poling of soda-lime and borosilicate glasses with concentrations of mobile ions (Na+, K+) that are processed with a non-blocking anode where hydrogen ion injection occurs. The model is compared with numerical solutions based on the drift-diffusion equations and Poisson's equation and shows good agreement. The increase in the concentration of the indigenous species with the lower mobility (K+) below the poled layer within a pile-up region is accurately modelled.

Analysis of static electric field characteristics of ships in flowing medium

At present, the model of ship corrosion electrostatic field mainly analyzes the electrostatic field distribution in the static medium under the given boundary conditions, without considering the actual corrosion of the metal on the ship’s surface in the flowing seawater, and the relationship between the electrochemical corrosion of the metal and the flow of the medium is very large, which results in a large error between the simulation results and the actual measurement results. In this paper, the relationship between corrosion electrostatic field and flow rate in flowing medium is theoretically deduced. Firstly, the distribution of liquid flow rate is analyzed, the thickness of boundary layer on the surface of metal plate is calculated, then the mass transfer process in flowing electrolyte is calculated by combining the flow rate distribution of metal surface medium, and the corrosion current density on the metal surface under the control of mass transfer process is calculated. Finally, the corrosion current density on the metal surface under the control of mass transfer process is calculated. The equivalent source model of electric field is established based on the current density, and the distribution of corrosion electrostatic field in the medium is analyzed. The correctness of the conclusion is verified by the finite element simulation and the ship model experiment.

Triboelectric and Piezoelectric Nanogenerators for Future Soft Robots and Machines.

SummaryThe triboelectric nanogenerator (TENG) and piezoelectric nanogenerator (PENG) are two recently developed technologies for effective harvesting of ambient mechanical energy for the creation of self-powered systems. The advantages of TENGs and PENGs which include large open-circuit output voltage, low cost, ease of fabrication, and high conversion efficiency enable their application as new flexible sensors, wearable devices, soft robotics, and machines. This perspective provides an overview of the current state of the art in triboelectric and piezoelectric devices that are used as self-powered sensors and energy harvesters for soft robots and machines; hybrid approaches that combine the advantages of both mechanisms are also discussed. To improve system performance and efficiency, the potential of providing self-powered soft systems with a degree of multifunctionality is investigated. This includes optical sensing, transparency, self-healing, water resistance, photo-luminescence, or an ability to operate in hostile environments such as low temperature, high humidity, or high strain/stretch. Finally, areas for future research directions are identified.