Symmetric Electric Field Research Articles

Electric Field Features and Charge Behavior in Oil-Pressboard Composite Insulation under Impulse Voltage

Oil-pressboard/paper insulation materials are essential in transformers for ensuring their safe and stable operation, primarily due to their roles in spatial electric field distribution and charge migration mechanisms. Current spatial distribution analyses rely on computational methods that lack empirical validation, particularly for oil-pressboard/paper composites. This study leverages the principles of the Kerr electro-optic effect to develop a rapid measurement platform for electric fields within oil-pressboard/paper insulation under impulse voltage conditions, which measures the spatial electric field characteristics using Cu-Cu and Al-Al electrodes under various scenarios: with asymmetric and symmetric pressboard coverage and different numbers of insulating paper layers. Findings indicated: (1) In asymmetric pressboard models, Cu-Cu electrodes exhibit a consistent peak electric field of approximately 16 kV/mm, while Al-Al electrodes show peak values of 18.13 kV/mm and −14.98 kV/mm. Charge density patterns are similar, with Cu-Cu at about 68 μC/m2 and Al-Al at 11.2 μC/m2 and −124.8 μC/m2. (2) Symmetric models present consistent peak electric fields and charge densities for both polarities. (3) Increasing insulating paper layers elevates electric field strengths. Both electrodes show the similar peak field of about 17 kV/mm with differing paper layers due to higher charge injection from the Al electrode. (4) Utilizing the Schottky effect and field emission principles, the study clarifies charge generation and migration mechanisms. These insights could provide a theoretical foundation for designing and verifying oil-pressboard/paper insulation structures in transformers.

Asymmetric electric field structure boosts photocharge spatial separation and transfer to enhance antibiotics removal: In-situ construction and directed induction

The symmetric electric field structure within layered Bi-based photocatalysts hinders the long-distance transport and spatial separation of bulk photocharges. Herein, the BiOI/BiOIO3 heterostructures featuring a strong interfacial electric field were prepared through in-situ hydrothermal reduction, disrupting the symmetry of the internal electric field in pristine BiOIO3. The intrinsic polarization electric field ({0 1 0}) and the interfacial electric field ({0 0 1}) within the BiOI/BiOIO3 heterostructure directionally induced the separation and transport of photocharges along distinct pathways, significantly enhancing the dynamics of photogenerated charges and improving photocatalytic activity. Specifically, with the addition of 15 mL of glycol, the CBI-15 sample with a BiOI/BiOIO3 structure achieved a 75.5 % removal rate of tetracycline and a 99.1 % removal rate of sulfisoxazole, which were 1.50 and 1.23 times higher than those of BiOIO3, respectively. Furthermore, continuous flow degradation experiments using photocatalytic membranes (CBI-PVDF) in real water media demonstrated the promising potential of CBI-15 for antibiotic removal. This work presents a novel approach to the directional induction of photocharges separation and transfer, providing valuable insights for developing highly efficient photocatalysts aimed at antibiotic removal.

Water structures in tip-charged carbon nanotubes.

Carbon nanotubes (CNTs) have potential applications in separation membranes and nanofluidic devices. It is well known that the behavior of water molecules confined in CNTs is affected by surface functional groups and external electric fields, leading to structural changes. The understanding of these structural changes of water within various CNTs is crucial, particularly in the context of material separation. While there have been many investigations into the effects of individual specific functional groups, a comprehensive understanding of the effect of these functional groups and the electric fields they generate on water molecules remains elusive. In this study, we investigate the properties of water molecules in tip-charged CNTs of (8,8), (10,10), and (12,12) chiral vectors with positive charges at one tip and negative charges at the other tip. Abstraction of ionized functional groups as tip charges enables a comprehensive understanding that is independent of individual functional groups. The symmetrically arranged tip-charges spontaneously generate a strong and symmetric electric field in the CNTs. However, the strength and directionality of the electric field are non-uniform and complex. In the interiors of (8,8) and (10,10) tip-charged CNTs, helical and square structures, which have disturbances caused by the non-uniformity of the electric field, are observed. The properties of the water molecules differed significantly in the center of the CNTs and near positive and negative charges, despite the electric field symmetry. In (12,12) tip-charged CNTs with 12 charges, a local ring structure is observed in the vicinity of negative charges but not in the vicinity of positive charges. It is concluded that the water structures in tip-charged CNTs have different characteristics from those in plain CNTs under a uniform electric field.

Study and analysis of high-power coupler failure due to asymmetric electric field distribution

Microwave vacuum electronics play a vital role in numerous applications, and high-power couplers are a critical component. However, coupler failure is a common problem in high-energy accelerators, especially in situations involving high continuous wave (CW) power operation, leading to costly downtime and reduced performance. This paper focuses on addressing the issue of coupler failure in high-power scenarios by studying the specific case of the Circular Electron-Positron Collider (CEPC) 650 MHz high-efficiency klystron, designed for a power of 800 kW and tested up to 700 kW. The failure was attributed to the cracking of the coupler ceramics due to asymmetric electric field distribution, a previously unnoticed issue. Consequently, this study describes the coupler testing process, analyzes the problem, and proposes corresponding solutions to achieve symmetrical electric field distribution and reduce thermal stress. After evaluating three approaches, we recommend the T-bar coupler with water cooling and forced air cooling as the most viable option. This research is significant for the future development of high-power couplers, as it offers references for overcoming technical challenges and optimizing structural designs. As a result, other high-power coupler designers may find inspiration in the suggested solutions as they strive for increased dependability and performance.

Symmetrical Localized Built-in Electric Field by Induced Polarization Effect in Ionic Covalent Organic Frameworks for Selective Imaging and Killing Bacteria.

Photocatalytic materials are some of the most promising substitutes for antibiotics. However, the antibacterial efficiency is still inhibited by the rapid recombination of the photogenerated carriers. Herein, we design a cationic covalent organic framework (COF), which has a symmetrical localized built-in electric field due to the induced polarization effect caused by the electron-transfer reaction between the Zn-porphyrin unit and the guanidinium unit. Density functional theory calculations indicate that there is a symmetrical electrophilic/nucleophilic region in the COF structure, which results from increased electron density around the Zn-porphyrin unit. The formed local electric field can further inhibit the recombination of photogenerated carriers by driving rapid electron transfer from Zn-porphyrin to guanidinium under light irradiation, which greatly increases the yield of reactive oxygen species. This COF wrapped by DSPE-PEG2000 can selectively target the lipoteichoic acid of Gram-positive bacteria by electrostatic interaction, which can be used for selective discrimination and imaging of bacteria. Furthermore, this nanoparticle can rapidly kill Gram-positive bacteria including 99.75% of Staphylococcus aureus and 99.77% of Enterococcus faecalis at an abnormally low concentration (2.00 ppm) under light irradiation for 20 min. This work will provide insight into designing photoresponsive COFs through engineering charge behavior.

Revealing Mie Resonances with Enhanced and Suppressed Second‐Order Nonlinear Optical Responses in a Hexagonal‐Prism‐Like MoS2 Nanoparticle

AbstractTransition metal dichalcogenides (TMDC), such as molybdenum disulfide (MoS2), have attracted great interest owing to their excellent electronic and optical properties. Efficient second harmonic generation (SHG) has been successfully demonstrated in the MoS2 monolayer, in sharp contrast to the negligible SHG from the bulk material. Here, the nonlinear optical responses of hexagonal‐prism‐like MoS2 nanoparticles are investigated, which support Mie resonances in the near infrared spectral range. It is revealed that the Mie resonances of such a MoS2 nanoparticle can be clarified into two types, which exhibit enhanced and suppressed SHG. It is verified that the SHG from the MoS2 nanoparticle is strongly correlated with the electric field distribution at the optical resonance. For the electric quadrupole mode with an anti‐symmetric electric field distribution, the SHG is greatly suppressed. As a result, a nanohole appears in the emission pattern of the SHG from the MoS2 nanoparticle. In sharp contrast, the SHG from the electric dipole mode with a symmetric electric field distribution can be one order of magnitude stronger than that from a MoS2 monolayer. The findings open new horizons for manipulating the nonlinear optical responses of TMDC nanoparticles and pave the way for realizing photonic devices.

Simulation study for efficiency optimization of multi-beam klystron output cavity

Increasing klystron tubes’ efficiency is essential in developing new-generation colliders and free-electron lasers. Different factors can affect the efficiency of a multi-beam klystron. One of the significant factors is the electric field symmetry inside cavities, especially in the output section. In this research, two different types of couplers are investigated in the extraction cavity of a 40-beam klystron. The first approach is a single slot coupler, which is frequently utilized and easier to fabricate but disturbs the electric field symmetry inside the extraction cavity. The second method has a more complex structure with symmetric electric fields. In this design, the coupler consists of 28 mini slots on the inner wall of the coaxial extraction cavity. Both designs are evaluated via particle in cell simulations, and the results exhibit around 30% more power extracted from the structure with a symmetric field distribution. The symmetric structures can also decrease the number of back-streamed particles by up to 70%.

Ionic wind generation through coplanar discharge: A plasma actuator without exposed electrodes

This study demonstrates the successful induction of a unidirectional ionic wind by adding an embedded electrode in a coplanar discharge, thus breaking the generation of a symmetrical electric field. The strategy for the ionic wind generation is based on separating the ionization process and the charged-particle acceleration process. Conventional plasma actuators used to induce an ionic wind typically incorporate exposed electrodes that pose a risk of unexpected airflow disturbance and reduce durability due to oxidation. However, the coplanar discharge-based, exposed-electrodeless plasma actuator developed in this study overcomes these issues. The coplanar discharge generates a diffused and uniform surface discharge, a desirable attribute for plasma actuators. The ionic wind velocity generated by this coplanar discharge plasma actuator is comparable to that generated by conventional plasma actuators when applying a square-waveform bias voltage to the additional electrode. Furthermore, this study emphasizes the significance of the phase difference between the repetitive pulses for generating coplanar discharge and the square-waveform voltage for accelerating the charged particles.

Axial ratio beamwidth enhancement of a low-profile circularly polarized antenna using defected ground structures

AbstractThis article explores the possibilities of incorporating a defected ground structure (DGS) for widening the 3 dB axial ratio beamwidth (ARBW) of a simple low-profile planar circularly polarized (CP) antenna. Two pairs of DGSs are etched symmetrically along the diagonals of the ground plane to overcome the limited 3 dB ARBW performance of a crossed-slotted circular-shaped planar CP antenna. Here, one pair of DGSs is orthogonal to another pair of DGSs. The distance between the pairs of DGSs plays a key role in enhancing the 3 dB ARBW by 40.62%. A gap of 0.18λ0 is considered between the DGSs to maintain the symmetrical electric field distribution in the substrate. It also helps to reduce orthogonal current components and provides uniformly distributed patch surface currents. These phenomena collectively help the proposed CP antenna to exhibit right-handed circular polarization radiation with the 3 dB ARBW of 186° and 188° in the E-plane and H-plane, respectively. The measured results yield impedance bandwidth (S11 ≤ −10 dB) of 2.6% (2.283–2.342 GHz), CP bandwidth of 0.9% (2.294–2.315 GHz), gain higher than 4.8 dBic, and total antenna efficiency more than 64% across the entire CP band.

Graphene Dirac fermions in symmetric electric and magnetic fields: the case of an electric square well

In this paper, a simple method is proposed to get analytical solutions (or with the help of a few numerical calculations) of the Dirac-Weyl equation for low energy electrons in graphene in the presence of certain electric and magnetic fields. In order to decouple the Dirac-Weyl equation we have assumed a displacement symmetry of the system along a direction and some conditions on the magnetic and electric fields. The resulting equations have the natural form to apply the technique of supersymmetric quantum mechanics. The example of an electric well with square profile is worked out in detail to illustrate some of the most interesting features of this procedure.

Modern Electromagnetic Field Theory and Its Application in Future Wireless Communication

With the advent of the 5G era, more and more technologies in life are applied to the technological development and theory of antennas. Waveform constraints. These basic applications are obtained due to the natural seismic source and the continuous arrangement and combination of arrays. In this article, we first discuss the spherically symmetric electric field distribution of antenna elements in space, and then discuss the influence of a circular array on the electromagnetic intensity of the space radiated field. At the same time, the basic characteristics of waveform restraint, array radar and array telescope are discussed. Afterwards, from a theoretical point of view, the physical properties and radiation characteristics of the near-field induction field and radiation field of the factory around the vibrator were analyzed quantitatively and qualitatively. Later, I discussed the relationship between an annular array and the eddy current. Through theoretical derivation and excitation factors, we used the original radiation equation to derive the Bessel function, and used a computer to make a simulation to explore the factors that can affect the array radiation.

Proton acceleration in vacuum using frequency-chirped laser pulses

Recent investigations demonstrate the achievement of protons with energies of several hundred MeV via vacuum laser acceleration mechanisms. However, the symmetric electric field from an unchirped laser pulse is not efficient in generating a high energy proton beam. It is known that a proton can gain energy from a chirped laser pulse through the optimal phase synchronization between the proton and the laser field. In this study, we investigate the proton acceleration by different frequency-chirped laser pulses in vacuum both analytically and numerically. We consider four different situations constituting the unchirped, linear, quadratic, and sinusoidal chirped laser pulses. For the unchirped laser case, the pulse symmetry results in no net energy gain for the proton from the laser field. Conversely, using frequency-chirped laser pulses renders high energy to the proton compared with the unchirped laser pulse. We compared three different chirped cases, and found that a sinusoidal chirped laser pulse renders maximum acceleration to the protons compared to the linear and quadratic chirped situations. There exists an optimal chirp parameter for each type of chirped laser pulse.

Relativistic dynamical inversion in manifestly covariant form

The relativistic dynamical inversion technique, a novel tool for finding analytical solutions to the Dirac equation, is written in explicitly covariant form. It is then shown how the technique can be used to make a change from Cartesian to spherical coordinates of a given Dirac spinor. Moreover, the most remarkable feature of the method presented here, which is the ease of performing a nontrivial change of reference frames, is demonstrated. Such a feature constitutes a potentially powerful tool for finding novel solutions to the Dirac equation. Furthermore, a whole family of normalizable analytic solutions to the Dirac equation is constructed. More specifically, we find exact solutions for the case of a Dirac electron in the presence of a magnetic field as well as a solution comprising a combination of a spherically symmetric electric field and magnetic fields. These solutions shed light on the possibility of separating the positive- and negative-energy parts of localized Dirac spinors in the presence as well as in the absence of magnetic fields. The presented solutions provide an illustration of the connection between the geometrical properties of the spinor and spin-orbit coupling for normalizable spinorial wave functions.

Dielectrophoretic stretching of drops of silicone oil: Experiments and multi-physical modeling

It is shown experimentally that drops of two pure silicone oils of different viscosities on a polypropylene substrate do not react to the in-plane electric field. Pre-treatment of silicone oil in a humid atmosphere at 80% relative humidity enriches oil with water-related ions and results in subsequent drop slight stretching under the action of the in-plane electric field. These phenomena demonstrate that the original silicone oils do not contain a sufficient concentration of any ions and counter-ions for the appearance of any Coulomb force or Maxwell stresses, which would result in drop stretching. However, a stronger stretching of silicone oil drops on the polypropylene substrate subjected to the in-plane electric field was experimentally demonstrated when 5 wt. % of TiO2 particles was suspended in oil. The particles behave as electric dipoles and, when subjected to a nonlinear symmetric electric field, experience dielectrophoretic force, which attracts them to both electrodes in air and oil. 3D simulations of the dielectrophoretically driven evolution of silicone oil drops laden with TiO2 particles also revealed a significant drop stretching in the inter-electrode direction in qualitative agreement with the experimental data. Still, numerical simulations predict an unbounded stretching with two tongues developing at the two drop sides. This prediction disagrees with the experiments where the dielectrophoretically driven stretching ceases and steady-state drop configurations without tongues are attained. This disagreement is probably related to the fact that in the experiments, TiO2 particles settle onto the substrate and are subjected to significant additional friction forces, which could ultimately arrest them.

Molecular Investigation of the Actuation of Electrowetted Nanodroplets

It is well known that the wettability of a droplet on a solid substrate can be modified by the application of an electric field. The phenomenon of electrowetting along with the associated physics of droplet shape change and dynamics has traditionally been studied at the micro-scale leading to exciting applications. The present work is undertaken to explore the physics of electrowetting actuation of droplet movement at the molecular level. Molecular simulations are performed to obtain the dynamic spreading of the droplet under the action of a radially symmetric electric field on a silica substrate. The dynamic behavior of the contact diameter is found to be qualitatively similar to that observed at the laboratory scale. Further simulations of droplet actuation across an array of electrodes illustrated the dynamics of the center of mass, which is then used to estimate the contact line friction and compared with the predictions from a reduced-order model. A scaling analysis is used to probe the physics of the problem correlating the contact line friction coefficient and the droplet velocity after actuation. The results and understanding elicited from the fundamental approach have the potential to guide the development of quick and precise control of nano-sized droplets and may prove to be pivotal in the development of future nanofluidic systems, nanomanufacturing methodologies, and high-resolution optoelectronic devices.

Strong magnetoelectric coupling at an atomic nonmagnetic electromagnetic probe in bismuth ferrite

Isolated nonmagnetic substitutional defect ions experience huge coupled electric magnetic interaction in the single-phase multiferroic ${\mathrm{BiFeO}}_{3}$. In the ferroelectric state above the magnetic N\'eel temperature ${T}_{N}$, the electric environment generates a single symmetric electric field gradient (EFG) parallel to the electric polarization direction. Below ${T}_{N}$, a distinct magnetic interaction arises, monitored by the probe nuclei via their magnetic moment. Two magnetic environments arise, given by the relative angle of the local magnetic moment within its easy magnetic plane with respect to the EFG orientation. The angle between field gradient orientation and magnetic field direction is the most stable fitting parameter. The magnetic interaction concomitantly increases the EFG dramatically which reflects an outstandingly large local magnetoelectric coupling. In the set of best fits, two different electric environments form concurrently with two distinctly different local magnetic fields. The magnetic ordering in ${\mathrm{BiFeO}}_{3}$ thus completely distorts the electric environment of the nonmagnetic probe nucleus. The implications for the local effect of dopants in ${\mathrm{BiFeO}}_{3}$ are discussed. A third probe environment arising independent of temperature is identified and associated with an iron vacancy.

On spin-lattice relaxation of nuclear quadrupole resonance in polycrystalline solids

The analysis of spin–lattice relaxation in nuclear quadrupole resonance (NQR) of spin-52 reported by Okubo and Igarashi (Z. Naturforsch. A. 56 (2001) 777) is extended to take account of the distribution of the initial non-equilibrium populations created by a resonant radio-frequency pulse in powder. The proposed theory is applicable to axially symmetric electric field gradient tensor and is examined for spin–lattice relaxation of 127I NQR in polycrystalline pyridine iodine monochloride measured at 469 MHz at 77 K.

Mutual Orientation of Electric Intracrystalline and Magnetic Fields in Iron Borate Single Crystals

X-ray structural analysis, Mössbauer spectroscopy, and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ab initio</i> calculations are used to study the structural properties and refine the orientation of intracrystalline fields in FeBO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> crystals in the region of the magnetic phase transition. It is found that in the temperature range of 293–403 K, the trigonal lattice parameters increase monotonically. Analysis of the electron density distribution maps does not show visible local disordering over the entire investigated temperature range. It is found that iron borate has an axially symmetric electric field gradient (EFG) whose main axis is directed along [001]. This orientation is maintained above and below the Néel point. In the magnetically ordered state of the crystal, the main axis of the EFG is orthogonal to the direction of the hyperfine magnetic field at iron nuclei. The results obtained will be used to develop a theoretical model of the formation of hyperfine structure in iron borate, which is important for applications of such crystals in next-generation synchrotron technologies.

Capture and translocation of a rod-like molecule by a nanopore: orientation, charge distribution and hydrodynamics.

We investigate the translocation of rods with different charge distributions using hybrid Langevin dynamics and lattice Boltzmann (LD-LB) simulations. Electrostatic interactions are added to the system using the P3M algorithm to model the electrohydrodynamic interactions (EHI). We first examine the free-solution electrophoretic properties of rods with various charge distributions. Our translocation simulation results suggest that the order parameter is asymmetric during the capture and escape processes despite the symmetric electric field lines, while the impacts of the charge distribution on rod orientation are more significant during the capture process. The capture/threading/escape times are under the combined effects of charge screening, rod orientation, and charge distributions. We also show that the mean capture time of a rod is shorter when it is launched near the wall because rods tend to align along the wall and hence with the local field lines. Remarkably, the orientational capture radius we proposed previously for uniformly charged rods is still valid in the presence of EHI.

A Broadband Circular Waveguide Rotary Joint With Substrate Integrated Coaxial Line Feeder

This paper proposed a broadband circular waveguide rotary joint with substrate integrated coaxial line (SICL) feeder. The SICL feeder can effectively convert TEM mode in the SICL into TM210 and TM020 modes in the multi-mode substrate integrated circular cavity (SICC). The annular slot on the surface of SICC can provide strong coupling between the SICC with TM210 and TM020 modes and the circular waveguide cavity with TM010 and TM011 modes. All the modes show symmetric electric field distribution. Thus, a wide bandwidth can be obtained due to six modes and strong coupling, and stable performance can be achieved while rotating because of symmetric field distribution. Comparing with reported circular waveguide rotary joints, the proposed design has the advantages of wide bandwidth and planarization of feeder. A prototype centered at 9.35 GHz is fabricated with a 10-dB impedance matching bandwidth of 24.6% and the insertion loss is between 0.82 dB to1.65 dB.