Spatial Electric Field Research Articles

Synergistic Effect of Au Interband Transition on Graphene Oxide/ZnO Heterostructure: Experimental Analysis with FDTD Simulation.

We furnish a comprehensive study on light-induced carrier generation due to the synergistic contribution of Au interband transition and graphene oxide (GO)/ZnO heterostructure. Plasmonic gold nanoparticles (Au_nps) are incorporated as a substructure sandwiched between GO and ZnO, assisting in additional photo-induced charge carrier generation. GO is prepared by a single-step plasma-enhanced chemical vapor deposition process. The GO/ZnO heterostructure having an active working area of 0.25 cm2 is created to unleash the pyroelectric property of ZnO, and subsequently, Au_np is introduced at the interface of GO/ZnO. Here, the interband transition of Au_np and its capability for charge carrier generation combined with the excitonic charge carrier generation of the highly crystalline non-centrosymmetric hexagonal wurtzite ZnO enhances the photoresponse. Furthermore, the interaction of Au_np with ZnO and its spatial electric field intensity distribution is demonstrated by finite difference time domain simulation which indicate toward an efficient carrier generation at the interface of Au_np and ZnO. The fabricated heterostructure has an active working wavelength in the UV-A region with the highest responsivity at 375 nm of the electromagnetic spectrum. The ultrafast response time (∼29 μs) of the device is due to the pyro-phototronic effect of the GO/ZnO heterostructure enhanced by the interband transition of Au. In the comparative study of the Au_np-enriched GO/ZnO heterostructure device with a GO/ZnO device, the former shows better performance. Both the devices work in the self-powered mode as well as the photoconductive mode, but with a higher on–off current ratio in the photoconductive mode. Hence, this work helps in properly understanding photo-induced charge generation in a Au interband transition enriched GO/ZnO heterostructure.

In vivo Measurements of Electric Fields During Cranial Electrical Stimulation in the Human Brain.

Cranial electrical stimulation (CES) has been applied at various current levels in both adults and children with neurological conditions with seemingly promising but somewhat inconsistent results. Stimulation-induced spatial electric fields (EFs) within a specific brain region are likely a significant contributing factor for the biological effects. Although several simulation models have been used to predict EF distributions in the brain, these models actually have not been validated by in vivo CES-induced EF measurements in the live human brain. This study directly measured the CES-induced voltage changes with implanted stereotactic-electroencephalographic (sEEG) electrodes in twenty-one epilepsy participants (16 adults and 5 children) and then compared these measured values with the simulated ones obtained from the personalized models. In addition, we further investigated the influence of stimulation frequency, intensity, electrode montage and age on EFs in parts of participants. We found both measured voltages and EFs obtained in vivo are highly correlated with the predicted ones in our cohort (Voltages: r = 0.93, p < 0.001; EFs: r = 0.73, p < 0.001). In white matter and gray matter, the measured voltages linearly increased when the stimulation intensity increased from 5 to 500 μA but showed no significant changes (averaged coefficient of variation <4.10%) with changing stimulation frequency from 0.5 to 200 Hz. Electrode montage, but not age, significantly affects the distribution of the EFs (n = 5, p < 0.01). Our in vivo measurements demonstrate that the individualized simulation model can reliably predict the CES-induced EFs in both adults and children. It also confirms that the CES-induced EFs highly depend on the electrode montages and individual anatomical features.

Numerical Simulation of Streamer Discharge Modeled by Drift-Diffusion Equations Based on SETD Method

Dynamic characteristics of streamer discharge in a parallel-plane electrode system are described within the framework of a drift-diffusion model coupled with Poisson’s equation at atmospheric pressure. The spectral-element time-domain (SETD) method is applied to the solution of streamer discharge problems, and the flux-corrected-transport (FCT) algorithm is also applied to suppress possible numerical divergence or numerical oscillation. The performance of the proposed method is examined in a number of numerical tests. Then the tempo-spatial evolutions of the streamer are obtained in detail under the different situations. Numerical results show that after the initial stage of adjustment, the streamers propagate in a steady-state mode, where the characteristics of the steady state are decided by background ionization frequency which is determined by pressure and background electric field together. And space charge effect is a dominant factor for the distortion of spatial electric field, making the discharge channel expand toward both electrodes faster. These works presented here are instructive for high-voltage insulating device protection and plasma application.

Research on Pre-Seismic Feature Recognition of Spatial Electric Field Data Recorded by CSES

In order to study the abnormal disturbance of the space ionosphere caused by strong earthquakes, the methods of SGF + WTA and EMD + ER are proposed and compared. The methods are applied to the 7.7 magnitude earthquake that occurred on the southern coast of Cuba on 29 January 2020 based on the electric field ultra-low frequency waveform data recorded by the ZH-1 electromagnetic satellite. Analyzing the electric field waveform data of the six orbits in and around the epicenter within five days before the earthquake and revisiting the orbit within two months, the significant information about the changes in the ionospheric electric field before the earthquake is obtained. The results demonstrate that: (1) in terms of time, large anomalies appeared before the earthquake on 16 January, and some orbital perturbations lasted until 2 February; (2) in terms of location, the disturbance changes are mainly concentrated over the central earthquake zone, and there are few conjugate zones; (3) in terms of amplitude, during the five days before the impending earthquake, most of the orbital disturbances exceeded the threshold of the background value while some of the orbital disturbances were less than the threshold; (4) in terms of morphology, the fluctuation that did not exceed the threshold appeared in the south of the earthquake area while a few appeared in the north. At the same time, the analysis method proposed in this paper is able to effectively extract the characteristics of electric field signal, clearly describe the abnormal signal change information before the earthquake, and provide a new method reference for the study of spatial electric field waveform data.

Power efficient Space Division Multiplexing–Wavelength Division Multiplexing system using multimode EDFA with elevated refractive index profile

SummarySpace division multiplexing (SDM) is an endowment technology to increase the collective bandwidth of multimode transmission in wavelength division multiplexing (WDM) system. In this paper, four wavelength signals from 229.6 to 232.6 THz are transmitted. For each wavelength, three linearly polarized (LP) modes are multiplexed using SDM. These 12 LP modes are transmitted through four parallel Multimode Step Index (MSI) fibers and received by four optical network units (ONUs). A multimode erbium doped fiber amplifier (MMEDFA) with elevated refractive index profile (ERIP) is used as preamplifier to this SDM–WDM system. This ERIP is complying with ITU‐T G.651.1 standard fiber in dispersion performance. The pumping power of 10 mW is adequate for this MMEDFA which is very low and cost effective. LP modes are transmitted, and performance of proposed transmission system is evaluated in terms of spatial electric fields, pumping power requirement, output optical power, and bit error rate (BER).

Electric field and spraying characteristics of electrospray using concave ground electrode

A curved surface is used as ground electrode for an electrospray system. An experimental study of ethanol electrospray is conducted to obtain the droplet size and velocity distribution, and the dispersity of droplet size distribution is calculated. The spatial electric field distribution of the ground electrode structures with different radii of curvature is obtained numerically. The results show that when the radius of curvature of the ground electrode is 50 mm, the mono-dispersity of the droplet size is the best, and the droplet size and velocity are small, also the distribution is uniform, and the spray atomization characteristics are superior.

Plasmon-Based Label-Free Biosensor Using Gold Nanosphere for Dengue Detection

In this study, a novel label-free immunosensor platform is developed to exploit the localized surface plasmon resonance (LSPR) phenomenon. The LSPR solution-based platform is designed by a gold nanospheres probe, functionalized with monoclonal anti-dengue antibody (IgG). Numerical calculations are performed to assess the LSPR extinction spectrum and spatial near electric field distribution around the nanoparticle surface. Important parameters that govern sensor performance, molecular and refractive index sensitivity are evaluated. On the evaluation of the platform as a molecular sensor, the detection of dengue NS1 antigens is presented. The results are consistent with the numerical simulations, which depicts the system’s ability to identify dengue NS1 antigen concentrations as low as 0.07 ± 0.01 µg/mL, along with fosters its potential application in plasmonic sensing.

Ion Motion Determines Multiphase Performance Dynamics of Perovskite LEDs

AbstractPerovskite light‐emitting diodes (PeLEDs) currently reach up to about 20% external quantum efficiency (EQE) and are becoming a promising technology for display and lighting applications. Still, many issues regarding their performance remain unresolved, particularly those related to stability, operation in non‐stationary regimes, and efficiency roll‐off at high current densities. Here, some of those issues in PeLEDs based on MAPbI3 perovskite are addressed. The authors analyze the electroluminescence (EL) and current dynamics after the first‐time voltage application and after application of sequences of voltage pulses, at different temperatures. Analysis of the results suggests that the complex dynamics observed on time scales from sub‐seconds to minutes and hours can be explained by the spatial redistribution of mobile species, most likely iodine interstitials, characterized by ≈175 meV activation energy. This redistribution alters the carrier injection, spatial electric field, and charge carrier density distributions as well as density of nonradiative recombination centers within the perovskite layer. Mathematical modeling of the ion motion and related processes enabled to reproduce the EL and current dynamics and to disentangle complex sequence of processes governing the PeLED operation.

Effect of applied low-voltage spatial electric field on the corrosion behaviour of copper in 3.5 wt-% NaCl solution

ABSTRACT Electrochemical tests and surface analyses were carried out to study the influence of the external low-voltage spatial electric field (SEF) on the corrosion behaviour of copper in 3.5 wt-% NaCl solution and explore the corrosion kinetics of copper under the SEF. The results show that the presence of the SEF aggravated the corrosion of copper; the results of weight loss tests and electrochemical tests indicated the enhanced corrosion rate of copper as the field strength increased. The X-ray diffraction results of corrosion products suggested that the Cu2O converted to Cu2(OH)3Cl with application of the SEF. The effect of the SEF on the copper proved the increase in corrosion rate was attributed to the enhanced migration of ions towards the sample surface caused by the external SEF. It resulted in more aggressive chloride ions to penetrate into the looser surface corrosion product film, thereby accelerating corrosion.

Enhanced dynamically assisted pair production in spatial inhomogeneous electric fields with the frequency chirping

Chirped dynamically assisted pair production in spatial inhomogeneous electric fields is studied by the Dirac-Heisenberg-Wigner formalism. The effects of the chirp parameter on the reduced momentum spectrum, the reduced total yield of the created pairs for either low or high frequency one-color field and two-color dynamically assisted combinational fields are investigated in detail. Also, the enhancement factor is obtained in the later two-color field case. It is found that for the low frequency field, no matter whether it is accompanied by the other high frequency field, its chirping has a little effect on the pair production. For the one-color high frequency field or/and two-color fields, the momentum spectrum exhibits incomplete interference and the interference effect becomes more and more remarkable as chirp increases. We also find that in the chirped dynamically assisted field, the reduced total yield is enhanced significantly when the chirps are acting on the two fields, compared with that the chirp is acting only for the low frequency strong field. Specifically, by the chirping, it is found the reduced pair number is increased by more than one order of magnitude in the field with a relative narrow spatial scale, while it is enhanced at least two times in other case of field with larger spatial scales or even in the quasi-homogeneous region. We also obtain some optimal chirp parameters and spatial scales for the total yield and enhancement factor in different scenarios of the studied external field. These results may provide a theoretical basis for possible experiments in the future.

PMN-PT nanoparticle/SnO2 nanofiber heterostructures: Enhanced photocatalytic degradation performance by ultrasonic wave induced piezoelectric field

Effective charge separation is of importance in increasing the efficiency of photocatalysts used in removing common industrial toxic dye in wastewater. The alternative spatial electric field produced by the piezoelectric effect, when combined with the semiconductor photocatalyst, can significantly accelerate the charge separation. In this study, lead magnesium niobate-lead titanate 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) nanoparticles and tin dioxide (SnO2) nanofibers were synthesized using colloidal coating method and electrospinning synthesis methods, respectively. PMN-PT@SnO2 composites were prepared as a novel heterostructured photocatalyst for the degradation of dye molecules in wastewater. Degradation of an organic dye pollutant in the presence of SnO2 nanofibers or PMN-PT@SnO2 nanocomposite photocatalysts were investigated under magnetic stirring and/or ultrasonic wave vibration conditions. Morphologies and electrical properties of pure and composite samples were also investigated. It was observed that the photocatalytic efficiency of PMN-PT@SnO2 piezoelectric-based photocatalysts could be increased by about 29% in the magnetic stirring and 32% in the ultrasonic wave vibration, respectively.

Realistic Electron Diffusion Rates and Lifetimes Due to Scattering by Electron Holes

AbstractPlasma sheet electron precipitation into the diffuse aurora is critical for magnetosphere‐ionosphere coupling. Recent studies have shown that electron phase space holes can pitch‐angle scatter electrons and may produce plasma sheet electron precipitation. These studies have assumed identical electron hole parameters to estimate electron scattering rates (Vasko et al., 2018, https://doi.org/10.1063/1.5039687). In this study, we have re‐evaluated the efficiency of this scattering by incorporating realistic electron hole properties from direct spacecraft observations into computing electron diffusion rates and lifetimes. The most important electron hole properties in this evaluation are their distributions in velocity and spatial scale and electric field root‐mean‐square intensity (). Using direct measurements of electron holes during a plasma injection event observed by the Van Allen Probe at , we find that when 4 mV/m electron lifetimes can drop below 1 h and are mostly within strong diffusion limits at energies below 10 keV. During an injection observed by the THEMIS spacecraft at , electron holes with even typical intensities (1 mV/m) can deplete low‐energy (a few keV) plasma sheet electrons within tens of minutes following injections and convection from the tail. Our results confirm that electron holes are a significant contributor to plasma sheet electron precipitation during injections.

Restraining Surface Charge Accumulation and Enhancing Surface Flashover Voltage through Dielectric Coating

A conductive metallic particle in a gas-insulated metal-enclosed system can charge through conduction or induction and move between electrodes or on insulating surfaces, which may lead to breakdown and flashover. The charge on the metallic particle and the charging time vary depending on the spatial electric field intensity, the particle shape, and the electrode surface coating. The charged metallic particle can move between the electrodes under the influence of the spatial electric field, and it can discharge and become electrically conductive when colliding with the electrodes, thus changing its charge. This process and its factors are mainly affected by the coating condition of the colliding electrode. In addition, the interface characteristics affect the particle when it is near the insulator. The charge transition process also changes due to the electric field strength and the particle charging state. This paper explores the impact of the coating material on particle charging characteristics, movement, and discharge. Particle charging, movement, and charge transfer in DC, AC, and superimposed electric fields are summarized. Furthermore, the effects of conductive particles on discharge characteristics are compared between coated and bare electrodes. The reviewed studies demonstrate that the coating can effectively reduce particle charge and thus the probability of discharge. The presented research results can provide theoretical support and data for studying charge transfer theory and design optimization in a gas-insulated system.

The properties of vertical electric field during haze event in Xi'an, China

This paper analyses the characteristics of vertical electric field (Ez) fluctuations and their correlation with other quantities during haze event in Xi'an, China. Our results indicate that in regard to long-period fluctuations (period > 30 min), when the RH (relative humidity) change rate is positive at the development stage of haze event, secondary chemical reactions increase the PM10 (particulate matter 10 μm or smaller in diameter) concentration. When the charge properties of particles are different, three types of spatial electric field changes occur. When the RH change rate is negative, if both the PM10 concentration and absolute value of Ez decrease, this suggests that the haze event has entered the dissipation stage. If the PM10 concentration and Ez do not change notably over time, this indicates that no secondary chemical reactions occur, and no new particles are produced. Regarding short-period fluctuations, Ez fluctuations with a period longer than 100 s notably contribute to the overall Ez fluctuations, and the Ez fluctuations exhibit a good correlation with the RH and PM10 concentration. In addition, Ez fluctuations with a period shorter than 30 s yield an important contribution to the overall Ez fluctuations, but the correlation between Ez fluctuations and the RH and PM10 concentration is poor, which indicates that Ez fluctuations with a period shorter than 30 s are not caused by RH variation. These results are of great significance to the identification of pollutant gases during haze periods and the prevention and control of haze events.

Thickness Effect of TiO2 Film Deposited on a Blade-Plate Electrode Surface on Breakdown Characteristics of Propylene Carbonate

Low-temperature plasma surface modification technology can help optimize the physical and chemical properties of materials. In this study, TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> films with thicknesses of approximately 100, 200, and 300 nm are prepared on an electrode surface using the magnetron sputtering method to explore the effect of film thickness on the breakdown characteristics of the liquid dielectric. The breakdown voltage of the liquid dielectric under a non-uniform electric field is determined using the Weibull distribution method. Based on the Kerr electro-optical effect, the changes in the spatial electric field along the symmetrical line of the blade-plate electrode gap are measured. The results show that compared to the undeposited state, the positive breakdown voltage of the liquid dielectric increases by 8.0%, 13.4%, and 15.9% corresponding to film thicknesses of 100, 200, and 300 nm, respectively, whereas the negative breakdown voltage increases by only 2.3%, 4.4%, and 5.7%. The TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film on the electrode surface has a greater impact on the increase in the breakdown voltage of the positive polarity, resulting in a decrease in the difference between the breakdown voltage of the positive and negative polarity. Therefore, it has great potential in improving the insulation performance of liquid dielectrics under uneven electric fields.

Research on the Non-Contact Pollution Monitoring Method of Composite Insulator Based on Space Electric Field

Through spatial electric field monitoring, it is expected to realize insulator pollution condition monitoring and contamination flashover warning in a non-contact way. Therefore, in this paper, the spatial electric field distribution characteristics of 110 kV composite insulators are simulated, where the effects of different surface states and their discharge levels on the spatial electric field of insulators are analyzed. On this basis, a non-contact monitoring method for composite insulator pollution based on the spatial electric field is proposed. The results show that there are significant differences in the spatial electric field of the composite insulator among three conditions, namely cleaning, pollution layer wetting, and dry band arcing. Increases of pollution layer wetting and dry band arcing would lead to an increase of the amplitude of the spatial electric field of the insulator. Verification experiments well indicated that it is feasible to identify the degree of pollution layer wetting as well as dry band arcing of the insulator string by fixed-point monitoring, the spatial electric field signal at the cross-strand of d = 0.5 m and directly opposite the last three positions. Research results can provide references for the online monitoring of overhead line polluted insulators and its flashover warning.

Study on the Construction and Application of Digital Twins on High Voltage Transmission Line Live Working Scenes

Affected by electric field generated in power transmission line, live worker on the high-voltage transmission line is in dangerous working environment. In this paper, posture perception, numerical simulation, and risk assessment are adopted to realize the deep fusion of physical trajectory and spatial virtual electric field distribution of live worker, and digital twin bodies of live worker in different live working scenarios are constructed. Firstly, posture trajectories and 3D model of living worker in typical operation conditions are captured and reconstructed by full-body inertial action capture technology and this technology use motion capture unit which include 3-aixs accelerometer/gyroscope/magnetic field sensors. The length of complex gap and body workspace under various live work scenes are also calculated. By static electrical field finite element (FE) numerical modeling, surface electrical field distributions of live worker under different posture trajectories are then calculated. Finally, interactive mechanism between “body-information-physical environment-virtual environment” is introduced, and potential risk of live worker is on-line assessed by live work guide rules. This work develops a new assessment and protection method for virtual training and field operations of high-voltage live worker. Which is of great significance for enhancing operation level and ensuring living workers’ safety.

Shaping liquid films by dielectrophoresis

AbstractWe present a theoretical model and experimental demonstration of thin liquid film deformations due to a dielectric force distribution established by surface electrodes. We model the spatial electric field produced by a pair of parallel electrodes and use it to evaluate the stress on the liquid–air interface through Maxwell stresses. By coupling this force with the Young–Laplace equation, we obtain the deformation of the interface. To validate our theory, we design an experimental set-up which uses microfabricated electrodes to achieve spatial dielectrophoretic actuation of a thin liquid film, while providing measurements of microscale deformations through digital holographic microscopy. We characterize the deformation as a function of the electrode-pair geometry and film thickness, showing very good agreement with the model. Based on the insights from the characterization of the system, we pattern conductive lines of electrode pairs on the surface of a microfluidic chamber and demonstrate the ability to produce complex two-dimensional deformations. The films can remain in liquid form and be dynamically modulated between different configurations or polymerized to create solid structures with high surface quality.

To the issue of the second harmonic generation in poled silicate glasses

Thermal relaxation of the second harmonic generation (SHG) observed in thermally poled soda-lime silicate glass is studied. At least two relaxation processes could be distinguished. Determined activation energy of the fastest SHG relaxation process is equal to about 0.5 eV. This SHG relaxation occurs at temperatures essentially below ones, at which the thermally stimulated depolarization current (TSDC) measurements show the relaxation of the spatial charge formed in thermal poling of the glasses. This confirms that SHG in poled glasses is not mostly conditioned by the “frozen” spatial charge and electric field of this charge.

Photogenerated charge dynamics of CdS nanorods with spatially distributed MoS2 for photocatalytic hydrogen generation

• A series of MoS 2 -loaded CdS NRs were prepared to study the photogenerated charge dynamics. • MoS 2 -tipped CdS NRs exhibited an excellent photocatalytic H 2 evolution activity. • MoS 2 deposited on the tips of CdS NRs gave a slow charge recombination. • Spatially longitudinal charge separation and transfer intensified by the MoS 2 tip was verified as a crucial factor. A series of MoS 2 -loaded CdS nanorods (NRs) have been successfully fabricated with the MoS 2 spatially distributed only on the tips or on the tips and walls of the CdS NRs, which impacted on photocatalytic H 2 evolution activity. MoS 2 -tipped CdS NRs were found to exhibit a better H 2 evolution performance (31.46 mmol h −1 g −1 ) than MoS 2 -coated CdS NRs (7.32 mmol h −1 g −1 ) and bare CdS NRs (2.96 mmol h −1 g −1 ). Kelvin probe force microscopy (KPFM) was used to identify the presence of a spatial electric field between the CdS NR and MoS 2 tip, with the electric field strongly inducing photogenerated electron-hole separation along the long axis of the CdS NRs and electron transfer to MoS 2 tips. The effect of longitudinal transfer of photogenerated electrons was confirmed by Pt photodeposition where it was found that Pt particles were photodeposited on the MoS 2 tips, whereas, in the case of pure CdS NRs and MoS 2 -coated CdS NRs, Pt particles were photodeposited on the walls and tips of the NRs, indicating a lack of spatially directional charge transfer. Time-resolved photoluminescence (TRPL) spectroscopy using band pass and long pass filters was employed to demonstrate that MoS 2 located on the tips of CdS NR can better separate photogenerated electron-hole pairs and suppress charge recombination. Consequently, slow charge recombination and spatially separated redox sites, deriving from MoS 2 tip engendered long distance of electron separation and transfer within the CdS NRs, give rise to the superior photoactivity by the MoS 2 -tipped CdS NRs. This study reveals the relationship between the MoS 2 distribution and photogenerated charge dynamics, and also provides greater insight into the performance of CdS-MoS 2 composites for photocatalytic H 2 evolution.