Value Of Electric Field Research Articles

Design of an Anti-Corona Device for HVAC Substation Connectors

One of the aspects to consider during high-voltage (HV) equipment design is the reduction in the probability of corona effect onset. Indeed, the corona effect is related to high electric field values beyond the equipment’s insulation levels and insulation strength, among other factors. This issue can be addressed during the design step, either by modifying the geometry of the electrical device or by including additional elements in the equipment structure to smooth out the voltage gradient along critical regions, such as anti-corona devices. The study of anti-corona devices for HV insulators is well documented, in contrast to substation connectors. Therefore, the present study proposed the design of a novel anti-corona device for HV substation connectors, including a method for the selection of its dimensions. This study shows that the relationship between the dimensional design variables and the critical electrical field on the connector is described by linear and rational functions. Thus, the design process times are cut down due to a reduction in the number of simulations required to run the assessment of the anti-corona device arrangement impact.

The Impact of Base Cell Size Setup on the Finite Difference Time Domain Computational Simulation of Human Cornea Exposed to Millimeter Wave Radiation at Frequencies above 30 GHz.

Mobile communication has achieved enormous technology innovations over many generations of progression. New cellular technology, including 5G cellular systems, is being deployed and making use of higher frequencies, including the Millimetre Wave (MMW) range (30–300 GHz) of the electromagnetic spectrum. Numerical computational techniques such as the Finite Difference Time Domain (FDTD) method have been used extensively as an effective approach for assessing electromagnetic fields’ biological impacts. This study demonstrates the variation of the accuracy of the FDTD computational simulation system when different meshing sizes are used, by using the interaction of the critically sensitive human cornea with EM in the 30 to 100 GHz range. Different approaches of base cell size specifications were compared. The accuracy of the computation is determined by applying planar sensors showing the detail of electric field distribution as well as the absolute values of electric field collected by point sensors. It was found that manually defining the base cell sizes reduces the model size as well as the computation time. However, the accuracy of the computation decreases in an unpredictable way. The results indicated that using a cloud computing capacity plays a crucial role in minimizing the computation time.

Near-Ideal Subthreshold Swing in InAlN/GaN Schottky Gate High Electron Mobility Transistor Using Carbon-Doped GaN Buffer

This work presents a comparative study of the subthreshold swing (SS) in InAlN/GaN-based high electron mobility transistor (HEMT), with and without carbon doping in the buffer layer. It is observed that devices with carbon-doped (C-doped) buffer exhibit near-ideal SS of close to 60-mV/decade over a wide range of drain voltage for both up and downsweep. The C-doped buffer layer reduces the OFF-state drain leakage current and increases the drain current ON/OFF ratio. TCAD simulation of the vertical electric field under the gate shows that the sample with a C-doped buffer layer has a much lower value of the peak electric field at the drain side edge of the gate, resulting in lower reverse-biased gate leakage current and smaller SS compared to that of the undoped buffer. Moreover, the junction capacitance at the interface of the unintentionally doped GaN (UID:GAN) and the C-doped buffer layer, in series with the depletion capacitance, reduces the overall capacitance, which further improves the SS in the C-doped wafer.

Comparative study on electrical and mechanical properties of UHV GIL post insulators

Post insulator is one of the key electrical components of DC GIL, which supports the central conductor and electrical insulation. The design of a safe, stable and reliable post insulator structure is related to the overall safety of the transmission system. In order to optimize the electrical and mechanical properties of single post insulator in UHVDC GIS, based on the finite element calculation method, a three-dimensional finite element simulation model of post insulator is established, and the electrical and mechanical properties of three kinds of post insulators with different structures are verified. The results show that the distribution of electric field and stress field on the surface of post insulator low-voltage end insert is relatively concentrated, and the maximum value of electric field and stress field of insulator appears at the gap of umbrella skirt; During the structural design, the surface of low-voltage end insert and the structure of insulator shed should be paid more attention.

Research on snow removal of energized UHV DC wall bushing

When the surface area of the wall bushing in the UHV DC converter station is polluted, there is a risk of wet snow flashover in the snow climate. The snow removal in time of the wall bushing can reduce the risk of outdoor insulation. For the horizontal insulator, we designed snow removal tests under the influence of various factors. The effect of various snow removal factors on the discharge characteristics were studied on the short insulator (4 m), while the UHV full-size wall bushing insulator (10.87 m) was studied by withstand test. The energized snow removal test results showed that under the same snow removal ratio, a position with a lower electric field value along the string should be selected as the starting snow removal position. Simultaneous snow removal on multiple sections was easier to cause surface discharge than the continuous long gap snow removal. The ratio and the degree of discharge appear to decrease first and then increase in a “spoon” shape. It was recommended to remove snow from the middle of the bushing firstly, and the first snow removal ratio in a continuous area was from 13% to 20% of the insulation distance. The research results of this paper can effectively guide the energized snow removal operation of ±800 kV DC wall bushings, and provide a reference for the energized snow removal operation of outdoor horizontal insulation equipment of other voltage levels.

Electromagnetic pollution analysis of Bitlis Eren University main and vocational school campus

In parallel with the development of technology, the increase in the number of devices emitting electromagnetic wave also increases the rate of electromagnetic pollution surrounding our environment. Determination of electromagnetic pollution level is of great importance for human health. In the present study, it was aimed to measure the electric field values of Bitlis Eren University main campus and vocational school campus in Turkey. Spectran HF60105 was used to perform the measurements at different 20 regions in different times. Based on the electric field values, the magnetic field and power density values were calculated for each location. It is found that the electric field values are below the limits which are determined by international standards.

Influences of Soil Water Content and Porosity on Lightning Electromagnetic Fields and Lightning-Induced Voltages on Overhead Lines

This study is performed to analyze the effects of both soil water content and porosity, two of the influencing factors of the finite conductivity, on the propagation of lightning electromagnetic fields (LEMFs) and lightning-induced voltages (LIVs) on overhead lines. A two-dimensional finite difference time domain (FDTD) model together with an improved Archie’s soil model is adopted for the field calculation at close distances from the lightning channel. The obtained results confirm that the soil water content and porosity have notable impacts on the peak values of LEMFs, especially the horizontal electric field. Moreover, the soil water content and porosity are correlated when acting together. The peak values of the horizontal electric field are found to be markedly influenced by the porosity changes at high water content or the water content changes at low porosity. The LIVs on overhead lines in these two cases are also studied. There appear to be greater differences in the induced voltages as the water content changes at low porosity.

SiO2 Microsphere Array Coated by Ag Nanoparticles as Raman Enhancement Sensor with High Sensitivity and High Stability.

In this paper, a monolayer SiO2 microsphere (MS) array was self-assembled on a silicon substrate, and monolayer dense silver nanoparticles (AgNPs) with different particle sizes were transferred onto the single-layer SiO2 MS array using a liquid–liquid interface method. A double monolayer “Ag@SiO2” with high sensitivity and high uniformity was prepared as a surface-enhanced Raman scattering (SERS) substrate. The electromagnetic distribution on the Ag@SiO2 substrate was analyzed using the Lumerical FDTD (finite difference time domain) Solutions software and the corresponding theoretical enhancement factors were calculated. The experimental results show that a Ag@SiO2 sample with a AgNPs diameter of 30 nm has the maximal electric field value at the AgNPs gap. The limit of detection (LOD) is 10−16 mol/L for Rhodamine 6G (R6G) analytes and the analytical enhancement factor (AEF) can reach ~2.3 × 1013. Our sample also shows high uniformity, with the calculated relative standard deviation (RSD) of ~5.78%.

A machine learning based model accurately predicts cellular response to electric fields in multiple cell types

Many cell types migrate in response to naturally generated electric fields. Furthermore, it has been suggested that the external application of an electric field may be used to intervene in and optimize natural processes such as wound healing. Precise cell guidance suitable for such optimization may rely on predictive models of cell migration, which do not generalize. Here, we present a machine learning model that can forecast directedness of cell migration given a timeseries of previous directedness and electric field values. This model is trained using time series galvanotaxis data of mammalian cranial neural crest cells obtained through time-lapse microscopy of cells cultured at 37 °C in a galvanotaxis chamber at ambient pressure. Next, we show that our modeling approach can be used for a variety of cell types and experimental conditions with very limited training data using transfer learning methods. We adapt the model to predict cell behavior for keratocytes (room temperature, ~ 18–20 °C) and keratinocytes (37 °C) under similar experimental conditions with a small dataset (~ 2–5 cells). Finally, this model can be used to perform in silico studies by simulating cell migration lines under time-varying and unseen electric fields. We demonstrate this by simulating feedback control on cell migration using a proportional–integral–derivative (PID) controller. This data-driven approach provides predictive models of cell migration that may be suitable for designing electric field based cellular control mechanisms for applications in precision medicine such as wound healing.

Hybrid Grey Wolf and Finite Element Method (GWO-FEM) Algorithm for Enhancing High Voltage Insulator String Performance in Wet Pollution Conditions

The presence of wet pollution on the upper surface of a string insulator increases the electric field on the insulator surface, especially at the triple junction (pin-cement, cement-porcelain) as well as at the surrounding air of the insulator. The rise of the electric field leads to the ionization of the air surrounding the insulator. This phenomenon, called corona discharge, is accompanied by several consequences that are harmful to the electricity transmission network, such as electromagnetic interferences, energy losses, visible light, audible noise, and the destruction of materials by erosion. If favorable conditions are gathered, it may even cause the flashover of the insulator. Designing an optimal insulator shape that reduces this electric field value at the triple junction will be an important achievement in enhancing the performance of electrical grids. The objective of this paper is to evolve a hybrid algorithm based on the GWO-FEM for optimizing the shape and the electrical performance of a string insulator. To achieve this purpose, this work is structured in four parts. First, modeling of the insulator string geometry is conducted in Comsol-multiphysics, then FEM computation of the electric field on the polluted surface of the string insulator is completed, and the maximum electric field value at the triple junction is saved as the fitness function that will be sent to the GWO algorithm to be optimized (minimized). The third part of the work is devoted to the coding of the constrained (electrical and geometrical constraints) GWO algorithm in a Matlab interface, and finally, coupling the GWO code with the FEM code. This study is achieved in wet polluted conditions. The results are given in both 2D and 3D representations. From the obtained results we can confirm that the developed GWO-FEM hybrid algorithm for optimizing insulator strings is a very promising tool for designing and enhancing the shape and the electrical performance of insulators.

Improvement in nonvolatile memory operations for metal–ferroelectric–insulator–semiconductor capacitors using HfZrO2 and ZrO2 thin films as ferroelectric and insulator layers

Metal–ferroelectric–insulator–semiconductor (MFIS) capacitors were characterized to elucidate the optimum design schemes for the ferroelectric field-effect transistor applications. The Hf1−x Zr x O2 (HZO) thin films (18 nm) were prepared on the SiO2 and ZrO2 insulator layers (ILs) with different film thicknesses. The choice of 10 nm thick ZrO2 IL was found to be an optimum condition to properly balance between the values of electric fields applied to the HZO (E HZO) and ZrO2 (E IL) layers, leading to effective improvement in capacitance coupling ratio and to suppression of charge injection for the MFIS capacitors. Furthermore, the crystalline natures of the crystallized HZO films were also found to be strategically controlled on the ZrO2 ILs, which can additionally enhance the E HZO with reducing the E IL. As consequences, the MFIS capacitors using 10 nm thick ZrO2 IL exhibited the ferroelectric memory window as large as 2.5 V at an application of ±5 V, which corresponds to 2.7 times wider value, compared to that obtained from the device using 2 nm thick SiO2 IL. Long-time memory retention and robust program endurance were also verified for the fabricated MFIS capacitors.

Magnetoelectric gradient structures: Properties and applications

This paper is devoted to a comprehensive study on a new type of microwave structures named magnetoelectric (ME) gradient structures. These structures are studied in this paper to understand the possibilities and application principles in feasible devices. The structure under study was calculated at different values of the applied electric field and different values of the relative permittivity of the artificial dielectric layer. The layered multiferroic structure in inhomogeneous electric and magnetic fields was calculated on the basis of the previously proposed mathematical model. The eigenwaves spectrum for several considered cases was the result of the performed calculation. The concept of using ME gradient structures in the design of electronically controlled microwave devices is formed on the basis of the results of a numerical experiment. Structures of this type will preferably be used in electronically controlled devices for the directional transmission of microwave signals, as it was shown in the theoretical part of the paper.

Structural evolution and thermal runaway of refractory W and Mo nanotips in the vacuum under high electric field from PIC-ED-MD simulations

We performed multiscale-multiphysics simulations for W, Mo and Cu nanotips under high electric field to investigate their structural evolution and thermal runaway process. The critical electric field values for the electric prebreakdown condition are predicted to be 311 MV m−1, 570 MV m−1 and 675 MV m−1 for Cu, Mo and W nanotips respectively (R 0 = 1 nm, H 0 = 100 nm). The boiling point of the metal is found to be a good predictor of the critical electric field strength for the initiation of thermal runaway. For metal nanotips made of refractory metals such as W and Mo, the structural thermal runaway process is determined by the rapid growth of small protrusions and their subsequent sharpening and thinning under the high electric stress on the apex region. On the other hand, the more intense atomic evaporation of Cu metal nanotips is caused by the ejection of large droplets generated by recrystallization and necking of the molten region at the apex of the nanotip. The differences in the observed structural evolutions of nanotips between refractory metals and the Cu during the thermal runaway event clearly show the strong influence of melting and boiling points on the electric prebreakdown process in nanoscale.

Electromagnetohydrodynamic unsteady flow with entropy generation and hall current of hybrid nanofluid over a rotating disk: An application in hyperthermia therapeutic aspects

The objective of this article is to explore entropy generation in electromagnetohydrodynamic (EMHD) hybrid nanofluid flow across an unsteady rotating disk in the presence of Hall current, thermal radiation and viscous dissipation. In the present physical model, an innovative group of nanofluid model known as the hybrid nanofluid is being used, which is made of silver [Formula: see text] and ferrosoferric oxide [Formula: see text] with blood. The nonlinear differential equations are transformed into ordinary differential equations using suitable self-similarity variables, which are obtained using the homotopy perturbation technique (HPM). When compared to the numerical technique (Runge-Kutta method), the homotopy perturbation method (HPM) yields a more accurate and reliable conclusion. The graphical outcomes are portrayed for velocities, temperature, volume fractions, entropy generation, Bejan number, skin friction and Nusselt number with various values of dynamic parameters. The higher values of electric field enhance the radial and azimuthal velocities whereas the opposite nature for a magnetic field parameter. Temperature profile enhances by varying magnetic and electric field parameters. The entropy generation rises for higher values of radiation, magnetic and electric fields. This theoretical model consists of EMHD and thermal radiation cases through blood flow and it plays a significant role in biomedical applications especially radiofrequency ablation (RFA), magnetic resonance imaging (MRI), cancer therapy and tumor therapy.

IN-SITU 5G NR BASE STATION EXPOSURE OF THE GENERAL PUBLIC: COMPARISON OF ASSESSMENT METHODS.

New measurement methods and equipment for correct 5G New Radio (NR) electromagnetic field (EMF) in-situ exposure assessment of instantaneous time-averaged exposure (Eavg) and maximum extrapolated field exposure (Emax) are proposed. The different options are investigated with in-situ measurements around 5G NR base stations (FR1) in different countries. The maximum electric field values satisfy the ICNIRP 2020 limit (maximum 7.7%). The difference between Emax and Eavg is <3dB for the different measurement equipment at multiple sites in case there is only self-generated traffic. However, in a more realistic scenario, Eavg cannot be used to assess the exposure correctly due to influence of other users as the spatial distribution of user equipment (UE) influences Eavg, while Emax is not affected. However, when multiple UEs are collocated, there is no influence of the number of UEs. A broadband measurement can give a first impression of the RF-EMF exposure up to 700m, but is not enough to assess the 5G-NR exposure.

Dielectric Properties of Carbon-Like Nanotube Structure: Monte Carlo Study

In this paper, we study the thermal and dielectric properties of a carbon-like nanotube structure. The ferrielectric mixed spin (1,3/2) Blume–Capel Ising model has been investigated, using Monte Carlo simulations under the Metropolis algorithm. We illustrate the thermal and dielectric properties of different physical parameters. Besides, we examine the effects of the exchange coupling interactions, the external longitudinal electric and the crystal fields on the transition temperature. It is found that the polarization decreases toward a transition temperature and undergoing the paraelectric phase, faster for low values of the external longitudinal electric field and the exchange coupling interactions. Besides, the total polarization versus the crystal field undergoes two principal transitions and exhibits a first-order and a second-order transitions.

Electronic, Optical, and Elastic Properties of CaFI Monolayer and Acoustic Phonon Dispersion at Hypersonic Frequencies Using Density Functional Theory and beyond with Random Phase Approximation and Bethe-Salpeter Equation.

The extraordinary properties of graphene have motivated us to investigate a novel 2D compound. In this framework, we study the structural, vibrational, electronic, optical, and elastic properties of a new two-dimensional CaFI monolayer, using DFT, GW, RPA, and BSE methodologies. The phonon dispersion curve of the CaFI monolayer exhibited no unstable phonon modes, confirming that this 2D sheet is dynamically stable. Our GW calculations show that the indirect bandgap energy value of CaFI is 6.52 eV. Interestingly, the bandgap rapidly decreased by improving the electric field value. Our BSE computations indicate that this monolayer becomes translucent when the incident light frequency exceeds the plasma frequency (6.50 eV). Also, we have computed the second and third elastic constants of CaFI by combining the DFT and RPA approaches with the homogeneous deformation method. Additionally, the longitudinal acoustic phonon dispersion of CaFI was studied. We have determined that the longitudinal acoustic wave velocity in our sheet is higher than the LA wave velocity of germanium measured using Brillouin or ultrasonic techniques.

A time domain element differential method for solving electromagnetic wave scattering and radiation problems

In this paper, a simple and efficient numerical method named time domain element differential method (TD-EDM) is proposed to solve electromagnetic wave scattering and radiation problems. In the method, the governing equations as well as boundary conditions are directly solved in a strong-form formulation. The computational domain is discretized using isoparametric elements, and the spatial derivatives of basic variables appearing in the governing equations are calculated by a set of analytical expressions of partial derivatives of the element shape functions with respect to global coordinates, and time derivatives of the basic variable are computed using the Newmark time integration scheme. The absorbing boundary condition (ABC) is applied on the truncation boundary to absorb the outgoing waves, which realizes the numerical modeling of an open infinite region. The incident wave is induced in the total-field region by setting equivalent electromagnetic currents on the total-field/scattering-field (TF/SF) boundary. The TD-EDM equations at the nodes located near the total-field boundary are modified to satisfy the conditions that the electric field values of all nodes involved belong to either the total-field or the scattered field. The near-to-far-field transformation technique is used to calculate the far scattered field, and then the target's Radar Cross Section (RCS) is evaluated. Several numerical results including the radiation from a line current source and the target's Radar Cross Section (RCS) are given to validate correctness of the proposed method.

Linear and nonlinear optical properties of a superlattice with periodically increased well width under electric and magnetic fields

In this paper, we have studied the electronic and optical properties of GaAs/AlxGa1-xAs superlattice with periodically increased well width. Under effective mass approximation, the finite element method is used to obtain wavefunctions and corresponding energy eigenvalues for several electric field (F) and magnetic field (B) values. We have shown that the increasing well width has a major effect on the localization of the first two energy states. The direction of the applied electric field shifts the localization position of the probability density of electrons to the left and right. For B = 0 (according to the parameters used), F = 5 kV/cm (especially for the difference between the first two energy levels (E12)) is a critical value. While the E12 value decreases in the range from −30 kV/cm to 5 kV/cm, it increases for the 5 < F < 30 kV/cm range. This behavior causes a red or blue shift in the optical spectrum. Also, F = −30 kV/cm causes more change in the structure than F = 30 kV/cm. In addition, the localization of the electrons is observed in the center of the superlattice under applied magnetic fields. The optical absorption coefficients and the refractive index changes are affected by applied F and B intensities. We can say that the electro-optical features of the superlattice have changed significantly with the combined effect of F and B values. This is desired for semiconductor optical device applications to have stable performances.

Neutral Bremsstrahlung Emission in Xenon Unveiled

We present evidence of non-excimer-based secondary scintillation in gaseous xenon, obtained using both the NEXT-White TPC and a dedicated setup. Detailed comparison with first-principle calculations allows us to assign this scintillation mechanism to neutral bremsstrahlung (NBrS), a process that has been postulated to exist in xenon that has been largely overlooked. For photon emission below 1000 nm, the NBrS yield increases from about 10$^{-2}$ photon/e$^{-}$ cm$^{-1}$ bar$^{-1}$ at pressure-reduced electric field values of 50 V cm$^{-1}$ bar$^{-1}$ to above 3$\times$10$^{-1}$ photon/e$^{-}$ cm$^{-1}$ bar$^{-1}$ at 500 V cm$^{-1}$ bar$^{-1}$. Above 1.5 kV cm$^{-1}$ bar$^{-1}$, values that are typically employed for electroluminescence, it is estimated that NBrS is present with an intensity around 1 photon/e$^{-}$ cm$^{-1}$ bar$^{-1}$, which is about two orders of magnitude lower than conventional, excimer-based electroluminescence. Despite being fainter than its excimeric counterpart, our calculations reveal that NBrS causes luminous backgrounds that can interfere, in either gas or liquid phase, with the ability to distinguish and/or to precisely measure low primary-scintillation signals (S1). In particular, we show this to be the case in the "buffer" and "veto" regions, where keeping the electric field below the electroluminescence (EL) threshold will not suffice to extinguish secondary scintillation. The electric field in these regions should be chosen carefully to avoid intolerable levels of NBrS emission. Furthermore, we show that this new source of light emission opens up a viable path towards obtaining S2 signals for discrimination purposes in future single-phase liquid TPCs for neutrino and dark matter physics, with estimated yields up to 20-50 photons/e$^{-}$ cm$^{-1}$.