Value Of Electric Field Research Articles

Electrochemical impedance in ac diagnostics of weakly conducting media

Impedance ac diagnostics is regularly used to study the transport phenomena in conducting systems of differrent dimensionalities. A common reason for using ac methods that are more complex than dc methods is the possibility to exclude the influence on the current-voltage (I−V) characteristic of contact phenomena accompanying dc measurements. In some cases (2d electron systems over helium) dc transport measurements are impossible. In weakly doped semiconductors (diluted electrolytes), the situation is less critical, but problems with the ohmic properties of the conducting contacts remain. The analysis of the details of the formalism that determines the reaction of a conducting medium to an external disturbance depends largely on the form of Ohm’s law for a conductor introduced into the impedance circuit. If there is a reason to define this law by the formula j = σΕ, where j, σ, E correspond to local values of current density, conductivity, and transport electric field, the structure of complex resistance Z^F(ω) is considered as a force one. If there is a diffusion component in Ohm’s law then the structure of complex resistance Z^μ(ω) is considered as an electrochemical one. We describe a standard electrolytic capacitor in series RC with a step load in terms of force or complex electrochemical impedance. Comparison with experiment shows the electrochemical structure of the complex resistance.

EFFECT OF ALUMINUM FOILS NUMBER AND ITS LENGTH IN IMPROVEMENT OF ELECTRIC FIELD DISTRIBUTION OF HIGH VOLTAGE CONDENSER BUSHING

High voltage condenser bushing is one of the important component that is widely used in the high voltage system. At high voltage levels more than 52kV the distribution of electric field in condenser bushing is irregular between the lead conductor and the grounded metallic flange. This paper studied the effects of changing in both: the number layers of aluminum foils and Oil Impregnated Paper (OIP), increasing the length of aluminum foils layers, and also increasing the thickness of OIP layer on the distribution of electric potential and electric field in condenser bushing by using Finite Element Method (FEM) and built the bushing model in ANSYS software. The harmonic analysis was performed of the bushing model at maximum value of withstand voltage test at 50Hz, from the analysis results are obtained the maximum value of electric field on the inner and outer surface of the bushing, the obtained electric field values were good and acceptable compared to the permissible electrical stress values of the dielectric insulators. This work can also aid in the design of high voltage bushing stress control, a knowledge of the electrical field distribution in bushing geometry. Moreover, the results of analysis are shown as contour plots, graphs plotted, and tables.

Electric Field and Self-Heating Effects on the Emission Time of Iron Traps in GaN HEMTs

In this article, we separately investigate the role of electric field and device self-heating (SHE) in enhancing the charge emission process from Fe-related buffer traps (0.52 eV from ${E}_{c}$ ) in AlGaN/GaN high electron mobility transistors (HEMTs). The experimental analysis was performed by means of drain current transient (DCT) measurements for either: 1) different dissipated power ( ${P}_{D,\mathrm {steady}}$ ) at constant drain-to-source bias ( ${V}_{\mathrm {DS,steady}}$ ) or 2) constant ${P}_{D,\mathrm {steady}}$ at different ${V}_{\mathrm {DS,steady}}$ ’s. We found that: 1) an increase in ${P}_{D,\mathrm {steady}}$ yields an acceleration in the thermally activated emission process, consistently with the temperature rise induced by SHE and 2) on the other hand, the field-effect turned out to be negligible within the investigated voltage range, indicating the absence of the Poole–Frenkel effect (PFE). A qualitative analysis based on the electric field values obtained by numerical simulations is then presented to support the interpretation and conclusions.

Controlling the movements of E. faecalis bacteria that carry a negative electric charge with an electric field

One of the main problems of bacteria sensors is that sufficient numbers of bacteria cannot approach and attach to the sensor surface. In this study, it has been suggested that an external electrical field can be applied to bacterial sensors to eliminate this problem. Moving Enterococcus faecalis (E. faecalis) bacteria, which carry a negative electric charge, in a desired direction with the effect of an electric field is an example of this. The Ag/PS/Si/In structures used as the sensor platform in the experiments were produced on n-type single crystal silicon by electrochemical etching method with 50% porosity and 1–5 μm pore size. Bacterial approach and removal experiments were carried out by immersing this PS-based structure in fluids containing E. faecalis bacteria and applying an electric field of 0–5 kV/cm in forward and reverse directions. Physical properties of the Ag/PS/Si/In structure were examined by immersing them in fluids containing live and dead E. faecalis bacteria and applying a fixed 7 kV/cm electric field value for 0–3 h. All experimental results were analyzed by impedance spectroscopy technique.

Study of the electric field variation based on preliminary observations at the ENU cosmophysical complex in 2020

The atmospheric electric field Ez is the most urgent problem of study of the physics of the atmosphere and the processes occurring in it. The conducted studies show the relationship of the electric field with atmospheric processes. Monitoring its changes is necessary to solve practical problems. This article presents brief characteristics of the installation of the EFM-100 electrostatic fluxmeter of the scientific cosmophysical experimental complex at the L.N. Gumilyov Eurasian National University (ENU) and its experimental data obtained in 2020. The article presents the results of observation of atmospheric-electrical characteristics nearthe Earth's surface and monitoring of the electric field of the atmosphere of the city of Nur-Sultan, in particular, estimates of the variation of the electric field of the surface layer of the atmosphere during sunrise and sunset based on data obtained by the EFM-100 fluxmeter. The comparison of meteorological data with the data of the electric field strength of the atmosphere is given. The analysis of the days and months in September and October 2020, when the conditions of “good weather” were manifested, was carried out. The series of electric field data obtained at other measuring stations show the characteristic periodicity of the electric field behavior. It is established that the value of the atmospheric electric field increases during sunrise with the manifestation of the solar terminator effect. It is interesting to study the relationship between the magnitude of the electric field of the atmosphere and the intensity of the cosmic ray flux, especially in the case of Forbush effects. The data of the ENU ground-based experimental complex allows us to conduct research on the study of atmospheric physics, including atomic electricity, as well as their interaction with cosmic rays and meto-conditions.

Implementation of uniaxial perfectly matched layer based on hexahedron element in discontinuous Galerkin time domain

The uniaxial perfectly matched layer (UPML), an important link in the numerical calculation of the discontinuous Galerkin time domain (DGTD), truncates the size of the computational domain and absorbs the outward-travelling waves. In traditional DGTD, tetrahedral meshes are used to divide the computational domain. These meshes are also used in UPML. As the scope of the computational domain is wide, many meshes will be generated after the UPML division wraps the external part of the domain, thereby resulting in inefficient computation. The use of a UPML in DGTD form based on hexahedral meshes is proposed. The internal propagation and UPML regions are divided by a tetrahedral element and a hexahedral element, respectively. Among the relevant numerical examples given, a few cases are analysed to demonstrate the feasibility of the proposed method: the high efficiency of the UPML with hexahedral mesh, attenuation of electromagnetic waves inside the UPML, and relative error of the electric field values at the observation points.

A two-dimensional air streamer discharge modified model based on artificial stability term under non-uniform electric field at low temperature and sub-atmospheric pressure

In this paper, an improved air discharge fluid model under non-uniform electric field is constructed based on the plasma module COMSOL Multiphysics with artificial stability term, and the boundary conditions developed in the previous paper are applied to the calculation of photoionization rate. Based on the modified model, the characteristics of low temperature sub-atmospheric air discharge under 13 kV direct current voltage are discussed, including needle-plate and needle-needle electrode structures. Firstly, in order to verify the reliability of the model, a numerical example and an experimental verification were carried out for the modified model respectively. Both verification results show that the model can ensure the accuracy and repeatability of the calculation. Secondly, according to the calculation results of the modified model, under the same voltage and spacing, the reduced electric field under low temperature sub-atmosphere pressure is larger than that under normal temperature and atmospheric pressure. The high electric field leads to the air discharge at low temperature and sub atmospheric pressure entering the streamer initiation stage earlier, and has a faster propagation speed in the streamer development stage, which shortens the overall discharge time. Finally, the discharge characteristics of the two electrode structures are compared, and it is found that the biggest difference between them is that there is a pre-ionization region near the cathode in the needle-needle electrode structure. When the pre-ionization level reaches 1013 cm−3, the propagation speed of the positive streamer remains unchanged throughout the discharge process, and is no longer affected by the negative streamer. The peak value of electric field decreases with the increase of pre-ionization level, and tends to be constant during streamer propagation. Based on the previous paper, this paper constructs the air discharge model under non-uniform electric field, complements with the previous paper, and forms a relatively complete set of air discharge simulation system under low temperature and sub atmospheric pressure, which provides a certain reference for future research.

The effect of Li2CO3 sintering additive on the dielectric and tunable performance of (Ba0.91Ca0.09)(Zr0.2Ti0.8)O3-CuO ceramics

(Ba0.91Ca0.09)(Zr0.2Ti0.8)O3-2 mol% CuO + x mol% Li2CO3 ceramics are obtained at low sintering temperature (1100 °C) by solid-state reaction method to study the effect of Li2CO3 sintering additive on the structure, dielectric and tunable performance of (Ba0.91Ca0.09)(Zr0.2Ti0.8)O3-CuO ceramics. The XRD results suggest that Li+ occupies A site firstly (for x = 1 and 2) and then occupies B site (for x = 3 and 4). It brings to the variation of lattice structure, which results in the non-monotonic shift of Tm. The SEM shows that appropriate Li2CO3 sintering additive can promote the grain growth. The maximum average grain size obtained at x = 2 makes it possess a higher permittivity (8336) at room temperature and a larger tunability (48.03%) at a low bias electric field value of 7 kV/cm. Accompanied with its low tan δ (0.00286), a high FOM value of 167.95 is achieved. These results suggest that the prepared ceramics are more attractive to be used as tunable devices due to its low sintering temperature and high FOM at a low bias electric field.

Effect of high-voltage power lines electromagnetic field on growth and development of green bean (Phaseolus vulgaris L.)

Relevance. High voltage electric power transmission lines (HVEPTL) cover a fairly large area of agricultural land all over the world. Investigations of electromagnetic field effect on growth and development of plants are held in various countries. The reaction of individual plant species and even varieties to the electromagnetic field manifests itself in different ways. The network of HVEPTL is growing steadily in our region as well. Nevertheless, information about the effect of the electromagnetic field on bean plants is rather scares. The aim of the present work was to evaluate HVEPTL effect on the growth and development of vegetable beans, depending on the intensity of the electromagnetic field.Material and Methods. The work was achieved on green beans Phaseolus vulgaris L. (Sakfit, Pagoda, MBZ 556, Arishka cvs) grown in conditions of different electromagnetic field values under HVEPTL. Biometrical parameters, plant productivity, yield, dry matter, photosynthetic pigments content, ascorbic acid, total antioxidant activity and total phenolics were determined.Results. In the ranges of electric field values from (5-10) to (400-440) B/m and magnetic field from 0 to 0.53 μT a beneficial effect of electromagnetic field on accumulation of leaves photosynthetic pigments (15-65% increase of chlorophyll а and 6-52% increase of chlorophyll b), polyphenol content (increase up to 17%), antioxidant activity (1-15% increase), and dry matter content (2,5-11% increase) and beans ascorbic acid levels (12-28% increase) were registered. Accordingy, increased plants growth, development and productivity were demonstrated. Peculiarities of beans plants grown under HVEPTL included decrease leaves carotene levels at electric field level of 60-100 B/m (70 m form HVEPTL), and lack of correlation between chlorophyll and carotene in leaves and total antioxidant activity and phenolics content at the stage of technical ripening.

Higher order curvature corrections to the field emission current density

A simple expression for the Gamow factor is obtained using a second-order curvature-corrected tunneling potential. Our results show that it approximates accurately the “exact-WKB” transmission coefficient obtained by numerically integrating over the tunneling region to obtain the Gamow factor. The average difference in current density using the respective transmission coefficients is about 1.5%, across a range of work functions ϕ∈[3−5.5] eV, Fermi energy EF∈[5−10] eV, local electric fields El∈[3−9] V/nm, and radius of curvature R≥5 nm. An easy-to-use correction factor λP is also provided to approximately map the “exact-WKB” current density to the “exact” current density in terms of EF/ϕ. The average error on using λP is found to be around 3.5%. This is a vast improvement over the average error of 15% when λP=1. Finally, an analytical expression for the curvature-corrected current density is obtained using the Gamow factor. It is found to compare well with the “exact-WKB” current density even at small values of local electric field and the radius of curvature.

Correlation between dielectric, mechanical properties and electromechanical performance of functionalized graphene / polyurethane nanocomposites

Carbon-based electroactive polymers (EAPs) are core materials for actuator applications. Introducing conductive fillers into EAPs is considered an effective method to improve the actuating performance, due to the enhanced dielectric properties achieved. This work describes the elaboration and characterization of polyurethane (PU)/oxygen-functionalized graphene (OFG) composite films. Results revealed that for the nanocomposites, a large increase in dielectric constant was obtained without a great mechanical reinforcement, whereas there was no improvement in electromechanical performance as compared to pure polyurethane. The possible reasons for these discordant results were thus investigated with the help of multiscale studies. The importance of measuring the dielectric and mechanical properties under the same conditions as those used to drive actuators could be pointed out. Using high electric field values led to a better prediction of the electromechanical coefficient M31 for pure PU at low frequency, but did not completely explain the decreasing M31 found for the composites. The discrepancy could be due to the moderate adhesion between the polymer and the graphene nanoplatelets, but also to the competition between the increased dielectric constant and the decreased electric field seen by the polymer, induced by MWS interfacial polarization.

Study on Measurement Error of Power Frequency Electric Field Intensity Caused by Change of Air Dielectric Constant with Humidity

People are paying more and more attention to the influence of power frequency electric field on their living environment, so the measured value of power frequency electric field under AC transmission line becomes an important reference for judging whether the surrounding environment is polluted or not. In actual measurement, it is found that the measured value of electric field intensity in high humidity areas is often relatively large. This paper will investigate the influence of the change of air dielectric constant on electric field measurement. Through experiments and simulations, it is found that air dielectric constant increases with the increase of humidity, which increases rapidly before the ambient humidity reaches 75%, and increases slowly after the ambient humidity exceeds 75%. However, it was found by simulation that the change of air dielectric constant has no obvious influence on the surrounding electric field intensity. Therefore, the change of air dielectric constant is not the main factor leading to relatively large measured value of field intensity in high humidity areas.

First-principles calculations and experimental study of enhanced nonlinear and dielectric properties of Sn4+-doped CaCu2.95Mg0.05Ti4O12 ceramics

High dielectric permittivity (ε′ ≈ 2000―6900) was accomplished in Sn4+-doped CaCu2.95Mg0.05Ti4O12 ceramics while retaining a low loss tangent (tanδ ≈ 0.027―0.075). Further, significant improvements in the nonlinear electrical properties, such as high values of the breakdown electric field (Eb ≈ 1.2―1.3 × 104 V cm−1) and nonlinear coefficient (α ≈ 31), were achieved. In addition, the nonlinear electrical parameters significantly improved, which is consistent with the increase in the electrical resistivities of the grains and grain boundaries due to the decrease in the Cu+/Cu2+ ratio. According to our first-principles calculations, the Sn atom at the Ti site prefers to be close to the Mg atom at the Cu site, while the oxygen vacancy prefers to be located at large distances from the Sn and Mg co-dopants. This confirms that the dielectric behavior and the nonlinear electrical properties originate from the interface between the grain and grain boundary.

Classical Dynamics of Rydberg States of Muonic-Electronic Helium and Helium-Like Ions in a Weak Electric Field: Counter-Intuitive Linear Stark Effect

According to the existing paradigm, helium atoms and helium-like ions (hereafter, heliumic systems) in a relatively weak external static electric field do not exhibit the linear Stark effect—in distinction to hydrogen atoms and hydrogen-like ions. In the present paper we consider the classical dynamics of a muonic-electronic heliumic system in Rydberg states–starting from the concept from our previous paper. We show that there are two states of the system where the averaged electric dipole moment is non-zero. Consequently, in these states the heliumic system should exhibit the linear Stark effect even in a vanishingly small electric field, which is a counter-intuitive result. We also demonstrate the possibility of controlling the overall precession of the electronic orbit by an external electric field. In particular, we show the existence of a critical value of the external electric field that would “kill” the precession and make the electronic orbit stationary. This is another counter-intuitive result. We calculate analytically the value of the critical field and show that it is typically smaller or even much smaller than 1 V/cm.

Characteristics of Avalanche Charge Domain in High-Power GaAs Devices

The formation of avalanche charge domain in high-power GaAs device has been studied numerically. According to the numerical simulation results of the distribution of electric field in the bulk of the device, the variation rules of peak electric field within the domain and the domain width with the bias electric field, the carrier concentration, and the device length are obtained, respectively, and by the comparison of the variation rules with and without considering carrier impact ionization, the effect of the carrier impact ionization on the peak electric field and the domain width have been obtained. It shows that 1) the peak electric field is mainly determined by the bias electric field, the carrier concentration and the device length, and the domain width is mainly determined by the carrier concentration and the device length; 2) the carrier impact ionization and avalanche multiplication have a significant effect on the peak electric field and domain width; and 3) the value of the peak electric field and domain width are closely related to the position of domain in the direction of domain motion. Based on the variation of peak electric field and domain width, the formation of avalanche charge domain is discussed. Our results can deepen the understanding of breakover mechanism of GaAs devices and contribute to the optimization of GaAs devices performance.

Kinetic equation having the integral scattering term with a linear form of external electrical and magnetic fields

In many cases, nobody consider any kinetic equation where the collision integral does not use clearly the values of external electric and magnetic fields. But there is some reason to use in the collision integral the above fields and to consider the ratio of the averaged deBroglie wavelength to the free-path length.

Experimental study of the effect of water vapor on dynamics of a high electric field non-equilibrium diffuse discharge in air

We report results on the influence of relative humidity (RH) on the propagation speed, the intensity of the emitted light, the energy and the gas temperature of a pin-to-plane nanosecond pulsed discharge at atmospheric pressure in synthetic air. The discharge is generated under very high overvoltage (several tens of kilovolts) so that it propagates with a voluminous, diffuse, and stable pattern. It is shown that the water vapor content has a strong impact on the discharge dynamics for gas mixtures with high RH and for the highest electric field values. In particular, for voltage pulse amplitudes higher than 65 kV and RH higher than 30%, the propagation abruptly slows down and the light intensity profiles show a stronger emission at the pin which weakens in the rest of the gap. The electric energy is slightly lower in humid air, independently of water vapor concentration. Also, time and spatially resolved gas temperature measurements carried out for different voltages show a late and significant heating at the pin whatever the water vapor content. An evaluation of the energy consumed in fast heating processes is proposed, showing an increased energy consumption at the pin in highly humid air. Besides, the hypotheses allowing for the consideration of the rotational temperature of the second positive system (SPS) of nitrogen (N2(SPS)) as the gas temperature under high electric field conditions are discussed.

Prediction of inverse spin Hall devices based on the direct injection of carriers in L-valley of GaAs

Numerical simulations are carried out to estimate the inverse spin Hall voltage (V ISHE) as a function of applied electric field, dopant density and excitation energy for n-GaAs based opto-spintronic devices. Adopting a three valley rate equation model, an expression is derived for the density of spin polarized electrons accumulated in different valleys of conduction band. It is noted that an external electric field can be used to enhance the magnitude of V ISHE significantly, however the shape of curve depends upon the choice of excitation energy. A significant rise of V ISHE is noted beyond a critical value of electric field when the carriers are injected into Γ-valley of GaAs. On the other hand, a peak like behaviour is observed when hot electrons are injected into Γ-valley. A dual slope behaviour of V ISHE with applied electric field is noticed when carriers are injected directly into L-valley of GaAs, where a reasonable value of V ISHE can be predicted even for a modest value of electric field. Further, a peak like behaviour of V ISHE with dopant density is predicted irrespective of the choice of excitation energy. The optimum dopant density of n-GaAs based Inverse spin Hall devices is found to be ∼4 × 1016 cm−3. Theoretical predictions made in this work are critically important for the realization of next generation inverse spin Hall devices involving L-valley electrons.

The effect of high-k passivation layer on off-state breakdown voltage of AlGaAs/InGaAs HEMT

In this paper, the effects of different relative permittivity (εr) of the passivation layer on off-state breakdown voltage of AlGaAs/InGaAs HEMTs are analyzed by ISE-TCAD. It is shown that as εr value increases, the off-state breakdown voltage increases. When the εr value increased to 80, the off-state breakdown voltage increased from 17.23V to 24.13V by 40.9%. This is because the peak value of electric field at the proximity of gate edge is reduced with the increase of εr value and it can lead to the improvement of the off-state breakdown voltage of device. Meanwhile, the electric field peak value near the drain edge increases with the increase of the εr value, leading to an increase in the ionization probability of electron-hole ionization under the the grid-drain area. In addition, the results also show that the channel current (IDS) and transconductance (gm) of the device are slightly reduced by the passivation layer with a high εr value, while the specific channel on-resistance is hardly degraded. Therefore, the passivation layer with a high εr value can effectively improve the breakdown voltage of the device without sacrificing the DC characteristics of the device.

On the efficiency of CO2 conversion in corona and dielectric-barrier discharges

The regimes of CO2 discharges are considered in which conversion of CO2 molecules proceeds mainly due to dissociation by electron impact. The efficiency of this process is estimated in the framework of an approximate analytical approach, using various CO2 dissociation cross sections available in the literature. It is shown that the best fit with the set of experimental data of the conversion efficiency in corona and dielectric-barrier discharges, corresponding to the range of reduced electric field values higher than 90 Td, is provided by using, as the dissociation cross section, of the cross section by Phelps, for excitation of electronic states with the energy threshold of 10.5 eV.