Frequency Of Electric Field Research Articles

Alternating current polarization to enhance piezoelectric performance of single crystal composites

Pb-based relaxor piezoelectric single crystal composites (PSCCs) have attracted widespread attention for improving the bandwidth and sensitivity performance of acoustic transducers due to their excellent electromechanical and piezoelectric properties. Alternating current polarization (ACP) has been proven as an effective method for enhancing the dielectric and piezoelectric properties of relaxor-PbTiO3 single crystals. Herein, we investigated the effects of the amplitude, frequency, and cycle number of the poling electric field on the piezoelectric and dielectric performances of PSCCs and obtained the optimum poling condition of ACP. Compared with the traditional direct current poling method, both the dielectric permittivity (ε33T/ε0) and piezoelectric coefficient (d33) of the AC-poled PSCCs were both increased by up to 20%. Notably, the ACP PSCC with a volume fraction of 60% exhibited a high d33 of 1610 pC/N, which is superior to values previously reported for PSCCs. This work provides an alternative strategy for enhancing the properties of PSCCs and may contribute to the further development of piezoelectric applications.

Fuzzy Decision Algorithm for Health Impact Assessment in a 5G Environment

The widespread use of mobile phones and other wireless communication devices raises concerns about radiation’s impact on humans. A new algorithm for making decisions for the assessment of the biological impact of non-ionizing radiation is presented in this paper. The algorithm was developed according to ICNIRP (the International Commission on Non-Ionizing Radiation Protection) guidelines using fuzzy logic. Appropriate membership function choices and optimized fuzzy rule selections are crucial for fuzzy modeling. Fuzzy logic is widely applied for multiparameter process modeling using linguistic forms and mathematical expressions. A comprehensive analysis of 4G and 5G network parameters was carried out including electrical and magnetic field strengths, frequency ranges, power densities, and exposure times. The proposed hands-on fuzzy decision-making algorithm can be used for fast, easy, and reliable non-ionizing radiation risk assessment for the following social groups: residents, on-site workers, and professional users.

Electrical properties of tissues from a microscopic model of confined electrolytes

Objective. In the presence of oscillatory electric fields, the motion of electrolyte ions in biological tissues is often limited by the confinement created by cell and organelle walls. This confinement induces the organization of the ions into dynamic double layers. This work determines the contribution of these double layers to the bulk conductivity and permittivity of tissues. Approach. Tissues are modeled as repeated units of electrolyte regions separated by dielectric walls. Within the electrolyte regions, a coarse-grained model is used to describe the associated ionic charge distribution. The model emphasizes the role of the displacement current in addition to the ionic current and enables the evaluation of macroscopic conductivities and permittivities. Main results. We obtain analytical expressions for the bulk conductivity and permittivity as a function of the frequency of the oscillatory electric field. These expressions explicitly include the geometric information of the repeated structure and the contribution of the dynamic double layers. The low-frequency limit of the conductivity expression yields a result predicted by the Debye permittivity form. The model also provides a microscopic interpretation of the Maxwell–Wagner effect. Significance. The results obtained contribute to the interpretation of the macroscopic measurements of electrical properties of tissues in terms of their microscopic structure. The model enables a critical assessment of the justification for the use of macroscopic models to analyze the transmission of electrical signals through tissues.

Beat encoding at mistuned octaves within single electrosensory neurons

Beats are slow periodic amplitude modulations resulting from the superposition of two spectrally close periodic signals. The difference frequency between the signals sets the frequency of the beat. A field study in the electric fish Apteronotus rostratus showed the behavioral relevance of very high difference frequencies. Contrary to expectations from previous studies, our electrophysiological data show strong responses of p-type electroreceptor afferents whenever the difference frequency approaches integer multiples (mistuned octaves) of the fish's own electric field frequency (carrier). Mathematical reasoning and simulations show that common approaches to extract amplitude modulations, such as Hilbert transform or half-wave rectification, are not sufficient to explain the responses at carrier octaves. Instead, half-wave rectification needs to be smoothed out, for example by a cubic function. Because electroreceptive afferents share many properties with auditory nerve fibers, these mechanisms may underly thehuman perception of beats at mistuned octaves as described by Ohm and Helmholtz.

Rough FTO electrode interface effect upon ferroelectric switching dynamics in Ag/P(VDF‐HFP)/FTO capacitor structures

AbstractRough FTO electrode interface effect upon the characteristic ferroelectric polarization parameters and switching dynamics in Ag/P(VDF‐HFP)/FTO junctions is systematically evaluated by varying electric field amplitude and frequency. Structural and microstructural studies confirm the ferroelectric phase formation of P(VDF‐HFP) on FTO surface. Tilted rectangular P‐E loops have been recorded in the applied fields ranging over 156.25–468.75 MV/m measured between 250 mHz and 5 Hz frequency ranges. Giant saturation of 21.7 μC/cm2 and remnant polarization of 34.9 μC/cm2 has been noted at low frequencies due to the influence of high electric field induced leakage currents. The coercive field, saturation and remnant polarization response with increase in electric field amplitude and frequency of the applied signal are well fitted with classic domain growth model proposed by Kolmogorov‐Avrami‐Ishibashi. A switching time scales of 32.2–693 ms has been observed for forward switching while for backward switching it is noted as 22.1–618.8 ms, when measured at frequencies from 5 Hz to 250 mHz. Furthermore, the tilted P‐E loops are attributed to the excessive leakage currents due to the high surface roughness of FTO bottom electrode.

Effect of electric field frequency on double hysteresis loops and energy storage characteristics of Sm/Mn co-doped PMN-PT ferroelectric ceramics

The generation and control of double hysteresis loops in ferroelectrics are of great significance for understanding the polarization reversal and application of energy storage. For Sm/Mn ions co-doped 0.70PMN-0.30PT ceramics, results indicate that when Sm-doping content is 2.5 mol%, the Mn doping content is higher than 2.5 mol% and the frequency of the electric field is higher than 5 Hz, double hysteresis loops can be obtained. Low-frequency measurement can transform the double hysteresis loops into normal hysteresis loops. This phenomenon is analyzed by the difference in polarization reversal kinetics between spontaneous polarization and defect polarization.

Lead indium niobate-lead magnesium niobate-lead titanate based whispering gallery mode resonator

Whispering gallery mode resonators (WGMRs) have garnered significant interest due to their potential applications in the fields of electro-optic modulation and microwave to optical photon conversion. In this study, we have leveraged an electro-optic crystal, lead indium niobate-lead magnesium niobate-lead titanate (PIN-PMN-PT), to fabricate a high-quality WGMR. Our investigation revealed that the crystal composition used in this work is 0.24PIN-0.45PMN-0.31PT, and each element of the whole sample is homogeneously distributed. The dielectric properties of the sample revealed the necessity of limiting the temperature and external electric field frequency to below 100 °C and 106 Hz, respectively. The obtained optical quality factor value (Q value) of the resonator is ∼0.7 × 105. Impressively, our resonator could be conveniently tuned by exploiting the enormous inverse piezoelectric effect d31 of the crystal, thereby alleviating the need for precise fabrication. Furthermore, a theoretical analysis of our resonator revealed that a calculated resonance wavelength shift is within a broad range of 2.16 nm. Intriguingly, if the surface roughness of the resonator is reduced tenfold, we can increase the calculated Q value dependent on surface scattering by 104. Our finding showcases the tremendous potential of the PIN-PMN-PT crystal-based WGMR as versatile building blocks for a variety of applications in the burgeoning field of photonic technology.

Fluctuating Flexoelectric Membranes in Asymmetric Viscoelastic Media: Power Spectrum through Mechanical Network and Transfer Function Models

Flexoelectric liquid crystalline membranes immersed in asymmetric viscoelastic media is a material system model with physiological applications such as outer hair cells (OHCs), where membrane oscillations generate bulk flow. Motivated by this physiological process, here we extend our previous work by characterizing the force transmission output of our model in addition to viscoelastic fluid flow, since solid–fluid interactions are an essential feature of confined physiological flow and flow in immersed elastic structures. In this work, the rigidity of the confinement results in a passive force reception, while more complete solid–fluid interactions will be considered in the future. A significant contribution of this work is a new asymmetry linear viscoelastic electro-rheological model and the obtained implicit relation between force transmission and flow generation and how this relation is modulated by electric field frequency and the material properties of the device. Maximal force and flow are found at resonant frequencies of asymmetry viscoelastic bulk phases, flexoelectric and dispersion mechanisms through the elastic and Womersley numbers.

Enhanced mixing quality of ring-type electroosmotic micromixer using baffles

In this study, an attempt has been taken to enhance the mixing efficiency in a micromixer of two different concentration fluids using electrokinetic effects such as electroosmotic flow. Four microelectrodes are located at specific locations on the outer surface of the one ring-shaped micromixer chamber. In addition, rigid baffles at the inlet side of the microchannel have been considered to enhance the mixing quality. The computation is performed using the finite element-based solver. The influences of different parameters such as average inlet fluid velocity (U0), frequency of the alternating current (f), the voltage amplitude of the alternating current (V), angle of inclination of the baffles (α), and the orientation fashion of the baffles at the inlet side have been investigated to achieve best mixing quality. This technique produces rapid mixing in the microchamber. Higher mixing quality can be achieved by considering the baffles in a specific orientation. The best mixing quality (99.67%) is obtained at the low inlet velocity of 0.05 mm/s. On the contrary, the lowest mixing quality (15.78%) is concerned with the higher inlet velocity with a high frequency of AC electric field.

Dynamic antiferroelectric behavior of dielectric susceptibility of a ferroelectric heterostructure

The dynamic antiferroelectric behavior of dielectric susceptibility of a ferroelectric heterostructure (FEH) containing two different ferroelectric (FE) films with an antiferroelectric interfacial coupling between them has been investigated by means of a modified Landau theory appended Landau-Khalatnikov (L-K) equation. Two identical surface transition layers (STLs) within each film and a parameter β described discrepancies of physical properties enter two component films are considered, which is a more realistic model. Due to the competitive action of antiferroelectric coupling, STL, β and frequency of electric field, the dielectric susceptibility of system may present four or two peaks, exhibiting an antiferroelectriclike behavior or a ferroelectric behavior, respectively. We can obtain the characteristics of dielectric susceptibility for our need through appropriate option of these parameters.

Numerical Simulation of Trap Modulated Multi-Mobility Charge Transport Under AC Field

Based on the characteristics of charge distribution under AC electric field with a wide frequency range, this paper focuses on the applicability of the traditional bipolar charge transport model under AC field in oil-impregnated paper (OP) insulation by simulation. Three physical processes of charge injection, migration and trapping/detrapping are discussed. In reaction to the influence of amplitude variation of AC field on injection rate, the charge injection process is described by a concatenation of the Ohmic mechanism and the Schottky mechanism. On account of the correspondence between the frequency and carrier mobility, the single mobility mode is modified to the multi-mobility mode, which exhibits the effect of localized state differences in materials on charge migration. The charge hysteresis under AC field is to do with the trapped charges, so the multi-energy trap distribution model is adopted to reveal the matching relationship between the period of electric field and charge residence time in deep traps. By comparing the simulation results and experimental phenomena, the modified model achieves space charge accumulation under a wide frequency range, and the shape of charge distribution is similar to the experiments, which proves the validity of the model. Further, the simulation results demonstrate that the net charge accumulation decreases with the increase of the electric field frequency, while the total charge accumulation shows an inverse trend with frequency, which is related to the coexistence of positive and negative charges.

Coalescence and Break-Up Behaviors of Nanodroplets under AC Electric Field.

Water must be separated from water-in-oil (W/O) emulsion because of the corrosion it brings to the relative equipment in the process of transportation and storage. It is an effective method to apply external electric field to achieve high performance of separating small, dispersed water droplets from W/O emulsion; however, the coalescing micromechanism of such small salty droplets under AC electric field is unclear. In this paper, molecular dynamics simulation was adopted to investigate the coalescence and separation process of two NaCl-aqueous droplets under AC electric field and discuss the effect of AC electric field frequency, as well as the time required for contacting, the critical electric field strength, the dynamic coalescence process and the stability of the final merged droplet. The results show that the critical electric field strength of the droplet coalescence increases with the increase of frequency, while the time required for droplet contacting becomes shorter. The shrinkage function curve was applied to characterize the droplet coalescence effect and it was found that the droplets coalescence and form a nearly spherical droplet under the AC electric field with a frequency of 1.25 GHz and strength of 0.5 V/nm. When the electric field frequency is 10 GHZ, the merged droplet presents a periodic fluctuation with the same period as the AC electric field, which mainly depends on the periodic movement of cations and anions under the AC electric field. The results can provide theoretical basis for the practical application of electrostatic demulsification technology in the petroleum or chemical industry from the microscopic perspective.

Thermo-physical characteristics of 3C‐SiC structure subjected to microwave exposure: A molecular dynamics study

Silicon carbide (SiC) is widely used as a susceptor for microwave hybrid heating applications owing to its exceptional microwave absorbing characteristics. In practice, it is challenging to characterize the thermo-physical behaviour of the microwave irradiated SiC-based targets experimentally due to interference of integrated measurement devices with microwaves. In this article, molecular dynamics simulations were performed to understand the atomistic response of a bulk 3C‐SiC model during microwave heating. Atomistic simulations were performed at different electric field strengths (ranging from 0.1 to 0.5 V/Å) and frequencies (ranging from 100 to 500 GHz) to develop a numerical relationship between temperature and time in order to predict the thermal response of bulk 3C‐SiC. On the other hand, the physical characteristics of the bulk 3C‐SiC were determined by the plots between mean square displacement (MSD), time and diffusion coefficients. The results showed that at 0.5 V/Å electric field strength and 500 GHz frequency, the diffusion coefficient increased up to 88% as compared to the electric field strength of 0.1 V/Å at 500 GHz. A change of 75% in the physical phase of 3C‐SiC structure with respect to the initial structure was confirmed by the distorted density distribution profile.

Thermal and dielectric properties of PVDF/PEO/SiO2 nanodielectrics for flexible radioelectronic device technologies

Hybrid polymer nanocomposites (HPNCs) are innovative multifunctional materials, which are developed and intensively studied for their uses in the rapid evolution of flexible and lightweight device technologies. Accordingly, to contribute in this area, thermal properties of the crystal phases and the broadband radio frequencies dielectric dispersion and relaxation behaviour of the HPNC films based on poly(vinylidene fluoride) (PVDF)/poly(ethylene oxide) (PEO)/silica (SiO2) are formulated and studied by employing differential scanning calorimeter (DSC) and impedance/material analyzer (IMA). DSC thermograms of these semicrystalline HPNCs explained the wide range alteration in the crystals melting temperature of PVDF (153–167 ​°C) and PEO (59–72 ​°C) and the total degree of crystallinity (4–87%) with varying compositional ratio over the entire range of the PVDF/PEO blend host matrix and the dispersed amount of amorphous SiO2 nanomaterial up to 15 ​wt%. The dielectric dispersion behaviour of these HPNCs, at 20 ​°C, confirmed a non-linear decrease in permittivity with the increase of applied radio wave electric field frequency from 1 ​MHz to 1 ​GHz, which lies in the range of 6 to 2. At a fixed frequency, dielectric permittivity values exhibited an uneven variation with the increase of SiO2 amount and also the modification in the composition of polymer blend matrix in these composites. The analysis of dielectric loss spectra and relaxation processes revealed that these are low loss dielectrics and the presence of SiO2 nanoparticles in the polymer blend matrix impedes the chain segmental dynamics and the dipole reorientation. The electrical conductivity of these HPNCs enhanced in the range of 10−8 to 10−4 ​S/cm with the increase in frequency but it changed anomalously when the constituent amounts of the formulated composites are varied. The polymer crystals thermal properties and the dielectric and electrical conductivity dispersion behaviour of these materials are demonstrated with the consideration of polymer-polymer and polymer-nanoparticle hybrid interfaces and interactions. The experimental results evidenced the behaviour of PVDF/PEO/SiO2 films as tunable nanodielectrics with their compositions and could be used as insulator and dielectric substrate materials in the advances of flexible radioelectronics and energy storage devices.

Slow development of induced-charge electro-osmosis in cetyltrimethylammonium bromide solutions

Induced-charge electro-osmosis (ICEO) is an important phenomenon in microfluidics and has been widely studied. Existing studies, both theoretical and experimental, have shown that ICEO is fully developed in milliseconds after an electric field is applied. In this study, we experimentally found that ICEO of cetyltrimethylammonium bromide (CTAB) solutions takes several seconds to be fully developed after the electric field is applied, which is significantly different from the existing literature. To reveal the underlying mechanism of this slow development, we propose a phenomenological model for ICEO of CTAB solutions by incorporating a dynamic viscosity formula. The ICEO model successfully explains the slow development and attributes it to the thixotropy of CTAB solutions. In addition, we also found that ICEO velocity varies irregularly as CTAB concentration increases, which is due to the variations of viscosity and electrical conductivity of CTAB solutions. The ICEO velocity of CTAB solutions reduces as the electric field frequency increases, which is different from the existing literature. The findings may enrich the understanding of ICEO and promote the application in complex fluids such as biological fluids.

Influence of baric and thermobaric effects on dielectric properties of complex oxide ceramics La1.8Sr0.2Ni0.8Co0.2O4+δ

With a purpose to clarify the reasons for the manifestation of high dielectric permittivity (ε) of oxides with K2NiF4-type structure, the influences of pressure (up to 50 GPa) and thermobaric effects (T = 1273 K, P = 2.5 GPa) on the electrical properties of the appropriate La1.8Sr0.2Ni0.8Co0.2O4+δ oxide have been analyzed.Ceramic samples have been synthesized by the “solution combustion” method with diammonium citrate and subsequent sintering of pyrolysis products at 1473 К and thermobaric treatment (TBT). At room temperature, the dielectric constant of thermobarically treated ceramics was found to be an order of magnitude greater than ε of sample obtained by sintering. Complex studies of electrical properties in broad ranges of pressure, temperatures and electric field frequencies have shown that the permittivity values of La1.8Sr0.2Ni0.8Co0.2O4+δ ceramics are not only due to external causes determined Maxwell-Wagner effects on grain boundaries and heterogeneity. Internal causes, the main of which are associated with bulk processes of charge polarization and distortion of polyhedra when the structure deviates from ideal, as well as with polarization processes caused by polaron carriers, are discussed. The baric behavior of thermo-electromotive (thermo-emf) force for some number of cycles of increasing and subsequent decreasing pressure makes it possible to use the examined material as a conductive medium capable of operating with controlled thermo-emf values under conditions of pressure change.

Electrocatalytic Degradation of Rhodamine B Using Li-Doped ZnO Nanoparticles: Novel Approach.

In this paper, we discuss the preparation of Li-doped ZnO nanostructures through combustion and report on their structural, morphological, optical, and electrocatalysis properties. X-ray diffraction analyses show that the samples have a structure crystallized into the usual hexagonal wurtzite ZnO structure according to the P63mc space group. The scanning electron microscope images conceal all samples' nanosphere bundles and aggregates. The reflectance spectra analysis showed that the direct bandgap values varied from 3.273 eV (for pure ZnO, i.e., ZnL1) to 3.256 eV (for high Li-doped ZnO). The measured capacitance concerning frequency has estimated the variation of dielectric constant, dielectric loss, and AC conductivity against AC electric field frequency. The dielectric constant variations and AC conductivity are analyzed and discussed by well-known models such as Koop's phenomenological theory and Jonscher's law. The Raman spectra have been recorded and examined for the prepared samples. Rhodamine B was electro-catalytically degraded in all prepared samples, with the fastest time for ZnL5 being 3 min.

Eighteen years' experience with tumor treating fields in the treatment of newly diagnosed glioblastoma.

The prognosis of glioblastoma remains unfavorable. TTFields utilize low intensity electric fields (frequency 150-300 kHz) that disrupt cellular processes critical for cancer cell viability and tumor progression. TTFields are delivered via transducer arrays placed on the patients' scalp. Methods: Between the years 2004 and 2022, 55 patients (20 female), aged 21.9-77.8 years (mean age 47.3±11.8 years; median 47.6 years) were treated with TTFields for newly-diagnosed GBM, and compared to 54 control patients (20 females), aged 27.0-76.7 years (mean age 51.4±12.2 years; median 51.7 years) (p=0.08). All patients underwent gross total or partial resection of GBM. One patient had biopsy only. When available, MGMT promoter methylation status and IDH mutation was detected. Patients on TTFields therapy demonstrated improvements in PFS and OS relative to controls (hazard ratio: 0.64, p=0.031; and 0.61, p=0.028 respectively). TTFields average time on therapy was 74.8% (median 82%): median PFS of these patients was 19.75 months. Seven patients with TTFields usage ≤60% (23-60%, mean 46.3%, median 53%) had a median PFS of 7.95 months (p=0.0356). Control patients with no TTFields exposure had a median PFS of 12.45 months. Median OS of TTF patients was 31.67 months compared to 24.80 months for controls. This is the most extensive study on newly-diagnosed GBM patients treated with TTFields, covering a period of 18 years at a single center and presenting not only data from clinical trials but also a group of 36 patients treated with TTFields as a part of routine clinical practice.

Electrically Manipulated Vapor Condensation on the Dimpled Surface: Insights from Molecular Dynamics Simulations.

Random vapor nucleation leads to flooding condensation with degraded heat-transfer efficiency. Since an external electric field has a significant effect on manipulating droplets' motion, it is possible to be one of the effective methods to hinder flooding phenomena and improve the heat-transfer rate by applying the external electric field during condensation. However, the motion of nanodroplets is more sensitive to the electric field owing to the scale effect on the nanoscale. The effect of the electric field on growth has not explicitly been comprehended. This work studied the condensation processes on a nanodimpled surface under an electric field with various strengths and directions. The results showed that condensed droplets' growth under the electric field depends on the competition between the electric field force and solid-liquid interactions. Increased vertical electric field strength, the higher torsion by the electric field hindered the motion of vapor, decreased the collision frequency for water molecules with the cooled surface, and elongated the cluster when the electric field force dominates, thus deteriorating the condensation performance. While applying the horizontal electric field, the greater electric field strength leads to better condensation performance by the larger contacting area for heat exchange. A wetting transition induced by the electric field was observed when the electric field strength increased to a certain extent (E > 5.2 × 108 V/m in this study). When the V-shaped surface replaced the dimpled surface as the condensed substrate, the same wetting transition phenomena occurred under a more significant horizontal electric field strength, showing that this method is universal. Besides, different electric field frequencies influenced both the growth and the nucleation, thus exhibiting various condensation performances.

Magnetizable Membranes Based on Cotton Microfibers, Honey, Carbonyl Iron, and Silver Nanoparticles: Effects of Static Magnetic Fields and Medium-Frequency Electric Fields on Electrical Properties

In this work, we present the manufacturing process of magnetizable membranes based on cotton microfibers, honey, carbonyl iron, and three different concentrations of silver microparticles. Each membrane is used as a dielectric material for the fabrication of electrical devices. By using the plane capacitor method, the electrical capacitance and dielectric loss tangent are measured in a medium-frequency alternating field superimposed on a static magnetic field. From the obtained data, the time constants of the devices, the components of complex dielectric permittivity, and the electrical conductivity of the membranes as a function of the electric field frequency and magnetic flux density can be extracted. The results show that the obtained membranes can be useful for the fabrication of low-cost and environmentally friendly magneto-active membranes that are required for various technical and biomedical applications.