Electric Field Amplitude Research Articles

Performance enhancement of 1–3 piezoelectric composite materials by alternating current polarising

The performances of 1–3 piezocomposite materials under various poling conditions were compared and analysed. The dielectric, piezoelectric, and electromechanical properties of 1–3 piezocomposite materials were studied with variations in the electric field amplitude (Ep), poling frequency (f), and number of cycles (C). It was found that the piezoelectric coefficient (d33), free dielectric constant (ε33T/ε0), and electromechanical coupling factor (kt) of 1–3 piezocomposite materials exhibit an increase of 21.4%, 13%, and 10.7%, respectively, under the optimum alternating current poling (ACP) condition (f = 1.25 Hz, Ep = 2 kV/mm, C = 16), compared with that of the samples poled using the direct current polarisation (DCP) method. The studies of the domain pattern indicate that the performance enhancement originates from the remarkable regularly striped domain structure and high domain wall density in ACP-poled samples. Our results suggest that the ACP method is effective in enhancing the performance of composite piezoelectric materials, which possess great benefits and potential for application in acoustic/medical transducers.

Sensing of Yeast Inactivation by Electroporation

Irreversible electroporation is a treatment to control microorganisms in food without harming food palatable aspects. The treatment by electroporation is dependent on the electric field amplitude, pulse durations and pulse repetitions. This study was carried out as a further investigation on the effects of irreversible electroporation pulse amplitude on S. cerevisiae and methods to verify the occurrence of irreversible electroporation, such as cell viability hemocytometer, macroscopic impedance measurements, scanning electron microscopy and numerical simulations. Active yeasts in wine represent a small portion of the volume (<; 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> cell/mL), which challenges macroscopic impedance analysis. Irreversible electroporation proved to reach active yeast limits established by standards within 500 kV/m. We detected a 15% increase in the in pulse current measurements for a 100-fold yeast viability decrease to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> cells/ml. Scanning electron microscopic images show details of yeast surface damage which may be PEF-triggered. Electric fields above 1 MV/m on the cell wall and release of intracellular substance caused by membrane permeability increase may directly contribute to yeast inactivation. Electroporation combined with instantaneous current-voltage measurements may be an adequate procedure for reducing yeast numbers in the industry.

Co2FeAl Full Heusler Compound Based Spintronic Terahertz Emitter

AbstractTo achieve a large terahertz (THz) amplitude from a spintronic THz emitter (STE), materials with 100% spin polarisation such as Co‐based Heusler compounds as ferromagnetic layer are required. However, these compounds are known to loose their half‐metallicity in the ultrathin film regime, as it is difficult to achieve L21 ordering, which has become a bottleneck for the film growth. Here, the successful deposition using room temperature DC sputtering of the L21 and B2 ordered phases of the Co2FeAl full Heusler compound is reported. Co2FeAl is used as ferromagnetic layer together with highly orientated Pt as nonferromagnetic layer in the Co2FeAl/Pt STE, where an MgO (10 nm) seed layer plays an important role to achieve the L21 and B2 ordering of Co2FeAl. The THz generation in the Co2FeAl/Pt STE is presented, which has a bandwidth of 0.2–4 THz. The THz electric field amplitude is optimized with respect to thickness, orientation, and growth parameters using a thickness dependent model considering the optically induced spin current, superdiffusive spin current, inverse spin Hall effect, and the THz attenuation in the layers. This study, based on the full Heusler Co2FeAl compound opens up a plethora of possibilities in STE research involving full Heusler compounds.

The Calculation of Electric Field Caused by Distributed Charge

The potential and electric field responses in cylinder cavity with ceramics slice caused by distributed charge in X-ray environment were simulated with finite difference method. The numerical results indicate that the distributed charge in ceramics’ middle section is negative or positive, and positive of both sides. For the photon energies from 30 keV to 1 MeV with same fluence, distributed charge and electric field were decreased at first and then increased. Electrode has great effect to the potential and electric field responses. For different plating thickness, there exists minimum to the electric field amplitude, and for the plating, there exist optimal diameter and thickness. Distributed charge is calculated using Monte-Carlo particle transport code.

Deduction of Electric Field Module in a Multilayer of Isotropic Materials to Detect Surface Plasmons with a Graphical User Interface

Abstract Electric field module for any isotropic multilayer thin film structure, is presented as analytical deduction. Analytic expressions for the electric field distribution are developed initially for a monolayer isotropic system based on Airy's formulae and boundary conditions, with an incident monochromatic source of light. The transfer matrix method 2×2, is used to deduce the distribution of the forward and backward electric field amplitudes on the inner layers in a general multilayer thin film structure. Analytical results are simulated in Transverse-Magnetic (TM) and Transverse-Electric (TE) modes making evident (when takes place) an electric field enhancement due to surface plasmons resonance. A graphical user interface is created to make steady simulations and create new structures as desired, minimizing time and optimizing resources.

Determination of maximum electric field amplitude sustained by electron acoustic solitary waves in an unmagnetized plasma with kappa-distributed electrons

This manuscript investigates the maximum electric field amplitude sustained by nonlinear electron acoustic waves, without losing their initial structure, and propagating in an unmagnetized homogeneous plasma comprising cold inertial electrons, hot kappa-distributed electrons, and stationary ions. Using nonlinear fluid Maxwell’s equations in one dimension, traveling wave solutions have been derived in the wave frame, and negative potential solitary structures have been observed. Furthermore, a pseudo-potential method has been employed to determine the maximum electric field amplitude as a function of the dimensionless Mach number (M), initial density ratio of hot to cold electron species (Rn=nh0nc0), and spectral index (κ) of the hot electron species velocity distribution function. We find that at this maximum electric amplitude, the density of the cold electron fluid becomes singular and thus can be called the wave breaking limit [J. M. Dawson, Phys. Rev. 113, 383 (1959)]. Density singularity is an artifact of the cold fluid plasma model and actually diminishes if one introduces a nonzero temperature to the cold inertial electrons. In that case, we find that the maximum electric field amplitude gets modified and follows the same scaling as the ratio of cold to hot electron species temperature (σ=TecTeh), as obtained by Coffey [Phys. Fluids 14, 1402 (1971)], with electron thermal velocity derived for the wave breaking limit of electron plasma waves in a warm plasma.

Enhancing laser speckle reduction by decreasing the pitch of a chiral nematic liquid crystal diffuser

The artefact known as speckle can plague numerous imaging applications where the narrow linewidth of laser light is required, which includes laser projection and medical imaging. Here, we report on the use of thin-film chiral nematic liquid crystal (LC) devices that can be used to mitigate the influence of speckle when subjected to an applied electric field. Results are presented which show that the speckle contrast (a quantitative measure of the presence of speckle) can be significantly reduced by decreasing the pitch of the chiral nematic LC from 2700 to 244 nm. Further reduction in the speckle contrast can be observed by operating the diffuser technology at a temperature close to the chiral nematic to isotropic transition. At such temperatures, we observe a simultaneous improvement in the transmission of light through the device and a decrease in the electric field amplitude required for the minimum speckle contrast value. We conclude by presenting a laser projected image of the 1951 USAF target with and without the LC device to demonstrate the visual improvement as a result of the speckle reduction.

First-principles study of ultrafast and nonlinear optical properties of graphite thin films

We theoretically investigate ultrafast and nonlinear optical properties of graphite thin films based on first-principles time-dependent density functional theory. We first calculate electron dynamics in a unit cell of graphite under a strong pulsed electric field and explore the transient optical properties of graphite. The optical response of graphite shows a sudden change from the conducting to the insulating phase at a certain intensity range of the applied electric field. It also appears to be a saturable absorption (SA) in the energy transfer from the electric field to electrons. We next investigate a light propagation in graphite thin films by solving the coupled dynamics of the electrons and the electromagnetic fields simultaneously. It is observed that the SA manifests in the propagation with small attenuation in the spatial region where the electric field amplitude is about $4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}\phantom{\rule{4.pt}{0ex}}\text{to}\phantom{\rule{4.pt}{0ex}}7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}\phantom{\rule{0.16em}{0ex}}\mathrm{V}/\AA{}$.

A Study of the Electrical Fatigue Behavior of Lead Zirconate Titanate for Micro-Actuator Application in Hard Disk Drives

This research work reports the effect of electric field amplitude on fatigue behavior of lead zirconate titanate ceramics (PZT) for micro-actuator hard disk drive application. The soft PZT samples were subjected to bipolar electrical cyclic loads to study the fatigue behavior. The amplitudes of electric fields of 1.00, 1.25, and 1.50 kV/mm at 10 Hz of frequency were applied. Polarization-electric field (PE ) loops representing fatigue degradation were demonstrated. The fatigue behavior was indicated by the alternation of the size and shape of PE loops and remanent polarization (Pr). It was found that the remanent polarization decreased significantly with the number of loading cycles. Fatigue degradation was more pronounced in greater applied field. A mathematical model for fatigue degradation was proposed in this work.

Electron interference in atomic ionization by two crossing polarized ultrashort pulses

Formation of geometrically regular interference patterns in the photoelectron momentum distributions (PMDs) corresponding to the photoionization of atoms by two single-color, crossing ultrashort pulses is investigated both analytically and numerically. It is shown that, in contrast to the photoionization by monochromatic pulses, PMDs for the ionization by crossing and co-propagating broadband pulses are essentially different (unless both pulses are linearly polarized), namely, when one pulse is linearly polarized along the propagation direction, $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\mathbf{k}}$, of the circularly polarized (CP) pulse, then interference maxima (minima) of the ionization probability have the form of three-dimensional single-arm regular spirals which are wound along $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\mathbf{k}}$. Next, the interference maxima (minima) of the ionization probability by a pair of crossing elliptically polarized pulses have the form of either Newton's rings or two-arm Fermat's spirals, depending on the position of a detection plane. Remarkably, these regular patterns occur only for certain values of the pulse ellipticities, and they become distorted for CP pulses. For both above-mentioned pulse configurations, the features of interference patterns depend on the time delay between pulses, their relative electric field amplitude, and relative carrier-envelope phase. Our predictions, illustrated by the numerical results for the ionization of H and He atoms by two orthogonal pulses, are quite general and we expect them to be valid for the ionization of any randomly oriented atomic or molecular target.

Hybrid model of radio-frequency low-pressure inductively coupled plasma discharge with self-consistent electron energy distribution and 2D electric field distribution

Low-pressure radio-frequency (RF) inductively coupled plasmas (ICPs) are extensively used for materials processing. In this work, we have developed a hybrid model consisting of two-dimensional (2D) Maxwell equations with an open boundary, zero-dimensional Boltzmann equation under linear and quasilinear approximations, and a power balance equation. The hybrid model is capable of achieving a self-consistent description of the electron heating mechanism and electron kinetics for the RF ICPs at low pressures. This work presents an investigation of the influence of operating conditions on 2D distributions of electric field and power density, normalized electron energy probability function (EEPF) (effective electron temperature), and plasma density in a low-pressure RF Ar ICP using the hybrid model. The results show that the RF frequency and absorption power significantly affect the 2D distributions and amplitudes of electric field and power density. The normalized EEPF is almost independent of RF frequency and weakly dependent on absorption power but significantly modulated by pressure at low RF frequency. The plasma density is also almost independent of RF frequency but increases with absorption power and pressure. In addition, we have validated the hybrid model against experimental data obtained in the driver region of a two-chamber RF Ar ICP source, where the RF frequency is 13.56 MHz, the power range is 200–1000 W and the pressure range is 0.1–1.0 Pa. The hybrid model qualitatively (and even quantitatively for some cases) reproduces the experimentally normalized EEPF and plasma density. The discrepancies in these plasma parameters could be attributed to the simplified collision processes taken into account in the hybrid model. The developed hybrid model can help us to better understand the effect of discharge conditions on electron kinetics and electron heating mechanism, and to ultimately optimize the parameters of RF ICP sources.

Three-Dimensional Inversion of Controlled-Source Electromagnetic Data in Fanchang Region, Anhui Province

Fanchang area of Anhui Province is an important link in the middle and lower reaches of the Yangtze River. To study the distribution of rock mass near the surface of the area and the contact relationship between the strata, and to determine the possible ore body space, we carry out a 15km controlled-source electromagnetic(CSEM) survey. The observed data is the electric field amplitude data simulating wide-area electromagnetic. For the single-section electric field amplitude data of controlled source, because of the lack of magnetic field data, the impedance data needed for audio geomagnetic inversion cannot be formed. This paper uses the limited memory quasi-Newton(L-BFGS) method to perform a three-dimensional inversion with the source directly. The theoretical model test results show that the inversion method can recover the underground resistivity structure and obtain better anomalous body resolution. The three-dimensional inversion of the CSEM data in Fanchang area shows that we could get the best inversion results when the grid size is about 1/3~1/2 of the dot pitch, the background resistivity is 100 Ω·m, and the error level is 5%. The inversion result of the full-section data, including two sources, shows that the south and north end of the profile is high-resistivity, and the intermediate resistivity is low. However, in the middle of the profile, the resistivity is significantly higher than the two sides. Combined with geological data, this change reflects the distribution of strata/rock masses on the surface of the work area and the contact relationship between them. This consistency verifies the feasibility and necessity of three-dimensional source inversion for the CSEM field amplitude |Ex| data of multi-source and single profile. The underground three-dimensional resistivity structure can be effectively obtained by using the L-BFGS method with the controlled source.

Electric Mode Excitation in the Atmosphere by Magnetospheric Impulses and ULF Waves

Variations of vertical atmospheric electric field Ez have been attributed mainly to meteorological processes. On the other hand, the theory of electromagnetic waves in the atmosphere, between the bottom ionosphere and earth’s surface, predicts two modes, magnetic H (TE) and electric E (TH) modes, where the E-mode has a vertical electric field component, Ez. Past attempts to find signatures of ULF (periods from fractions to tens of minutes) disturbances in Ez gave contradictory results. Recently, study of ULF disturbances of atmospheric electric field became feasible thanks to project GLOCAEM, which united stations with 1 sec measurements of potential gradient. These data enable us to address the long-standing problem of the coupling between atmospheric electricity and space weather disturbances at ULF time scales. Also, we have reexamined results of earlier balloon-born electric field and ground magnetic field measurements in Antarctica. Transmission of storm sudden commencement (SSC) impulses to lower latitudes was often interpreted as excitation of the electric TH0 mode, instantly propagating along the ionosphere–ground waveguide. According to this theoretical estimate, even a weak magnetic signature of the E-mode ∼1 nT must be accompanied by a burst of Ez well exceeding the atmospheric potential gradient. We have examined simultaneous records of magnetometers and electric field-mills during &amp;gt;50 SSC events in 2007–2019 in search for signatures of E-mode. However, the observed Ez disturbance never exceeded background fluctuations ∼10 V/m, much less than expected for the TH0 mode. We constructed a model of the electromagnetic ULF response to an oscillating magnetospheric field-aligned current incident onto the realistic ionosphere and atmosphere. The model is based on numerical solution of the full-wave equations in the atmospheric-ionospheric collisional plasma, using parameters that were reconstructed using the IRI model. We have calculated the vertical and horizontal distributions of magnetic and electric fields of both H- and E-modes excited by magnetospheric field-aligned currents. The model predicts that the excitation rate of the E-mode by magnetospheric disturbances is low, so only a weak Ez response with a magnitude of ∼several V/m will be produced by ∼100 nT geomagnetic disturbance. However, at balloon heights (∼30 km), electric field of the E-mode becomes dominating. Predicted amplitudes of horizontal electric field in the atmosphere induced by Pc5 pulsations and travelling convection vortices, about tens of mV/m, are in good agreement with balloon electric field and ground magnetometer observations.

Fracture and electric‐field‐induced crack growth behavior in NBT‐6BT relaxor ferroelectrics

AbstractThe fracture properties of 0.94(Na0.5Bi0.5)TiO3‐0.06BaTiO3 (NBT‐6BT) relaxor ferroelectrics were investigated using the Vickers indentation method and computation of crack tip opening displacement. It was found that an unpoled sample had a fracture toughness of around 1.35 MPa m1/2. In contrast, an electrically poled sample exhibited anisotropy with a lower fracture toughness perpendicular to the poling direction and a higher value in the parallel direction, as compared to the unpoled sample. Upon cyclic electrical loading (with applied electric field amplitudes between 0.73EC and 1.4EC), the indented surface crack was found to propagate. In general, the crack grew rapidly during the initial cycles followed by crack arrest, and the principal driving force for crack growth was proposed to be residual stress around the indentation, as evidenced by the limited field dependence of crack growth. There was also a contribution from the electromechanical strain, which played a role at high cycles (&gt;100 cycles) and high fields (&gt;1.3 EC). Evidence of a saturation threshold of crack propagation is an advantage for the electromechanical reliability of relaxor ferroelectrics in devices.

The Discrepancy Between Simulation and Observation of Electric Fields in Collisionless Shocks

Recent time series observations of electric fields within collisionless shocks have shown that the fluctuating, electrostatic fields can be in excess of one hundred times that of the quasi-static electric fields. That is, the largest amplitude electric fields occur at high frequencies, not low. In contrast, many if not most kinetic simulations show the opposite, where the quasi-static electric fields dominate, unless they are specifically tailored to examine small-scale instabilities. Further, the shock ramp thickness is often observed to fall between the electron and ion scales while many simulations tend to produce ramp thicknesses at least at or above ion scales. This raises numerous questions about the role of small-scale instabilities and about the ability to directly compare simulations with observations.

Comparison of ULF electric field recorded by ground-based stations in China and a low-altitude satellite

The correlation and synchronization between ground-based and space-based electric field in calm period, is the basis for a comprehensive study of earthquake monitoring. However, it is difficult to study their relevance because of large dissimilarities on data records. The DC-ULF electric field recorded by the DEMETER satellite and the geo-electric field observed in ground-based stations in China were comprehensively analyzed in this paper. The results show that the ionospheric electric field after removing the additional electric field caused by the satellite motion in the magnetic field has a stable annual variation trend; both the annual variation trend and the amplitude of ionospheric electric field above different locations in China are similar. The synchronous, corresponding and similar significant annual variation trends of both ionospheric electric field and geo-electric field in the same direction and with same frequency were found above some locations. The trend displays higher value in summer and lower value in winter. The Sq (Solar quiet) current system is the main source for these phenomena. It is noticed that the shapes and amplitude of geo-electric field for different stations are different, largely due to their individual underground layer conductivity, water level and so on. It is of great significance to explore the correlation and consistency between ground-based and space-based data in order to recognize the anomalies related to the seismic activity and to understand the LAI (Lithosphere-Atmosphere-Ionosphere) coupling mechanism.

Об излучении поверхностного источника по нормали к границе полупространства и плоскослоистой структуры

On the basis of the rigorous theory of radiation from an elementary current source located at the boundary of a plane-layered structure, the radiation of an arbitrary distribution of the surface current is considered. A strict relationship is obtained between the normal-radiated fields generated by an arbitrary distribution of the external surface current in the half-spaces surrounding the plane-layered structure. It is shown that the ratio of the amplitudes of electric fields at the same distance from a source emitting in opposite directions, normal to a plane-layered structure, is determined by a simple algebraic expression that includes the electromagnetic parameters of the media and the thickness of the structure's films. Special cases are also considered: a surface radiation source at the boundary of one homogeneous film and a surface source at the boundary of two homogeneous half-spaces.

Non-linear dielectric response of layered CuInP2S6 and Cu0.9Ag0.1InP2S6 crystals

In this work, we report on the results of the examination of the nonlinear dielectric response of layered ferrielectic CuInP2S6 and Cu0.9Ag0.1InP2S6 crystals. The temperature behaviour of the nonlinear dielectric properties of ferrielectic CuInP2S6 and Cu0.9Ag0.1InP2S6 is found to be consistent with Landau theory. The additional peak of the third-order nonlinear susceptibility in these crystals, below the phase transition temperature, is strongly influenced by the electric field amplitude, and it is caused by the ferroelectric domain dynamics. The nonzero value of the second-order susceptibility and the mismatch between the temperatures of linear and third-order susceptibilities indicate that some polarisation exists above the phase transition temperature.

Estimate the electrical activity in a neuron under depolarization field

Abstract The physical electric variable is included into the known Hindmarsh-Rose (HR) model for estimating the depolarization field effect and then external current forcing is applied to detect the firing responses. Based on the proposed model, the effects of the amplitude and frequency of the sinusoidal current on the firing mode of the neuron are studied by using bifurcation analysis. It is found that there is a peak of firing interval of neurons with the increasing of stimulation current intensity. In the presence of electric field, the firing pattern of neuron is transformed from single busting to intermittent multimodal busting with the increasing of frequency and amplitude of electric field. The largest Lyapunov exponent is drawn for verification. In the absence of electric field, the two neurons coupled in the first variable achieve synchronization in busting mode. If there is an external electric field, the two neurons can achieve intermittent multimodal busting firing synchronization even without direct variable couple since the energy is injected into the coupled system by the external electric field. Our results show that the periodic external electric field and external current stimulation play an important role in the neuronal firing pattern.

Rapid, Dose-Dependent Enhancement of Cerebral Blood Flow by transcranial AC Stimulation in Mouse

BackgroundTranscranial electrical stimulation at an appropriate dose may demonstrate intracranial effects, including neuronal stimulation and cerebral blood flow responses. ObjectiveWe performed in vivo experiments on mouse cortex using transcranial alternating current [AC] stimulation to assess whether cerebral blood flow can be reliably altered by extracranial stimulation. MethodsWe performed transcranial AC electrical stimulation transversely across the closed skull in anesthetized mice, measuring transcranial cerebral blood flow with a laser Doppler probe and intracranial electrical responses as endpoint biomarkers. We calculated a stimulation dose–response function between intracranial electric field and cerebral blood flow. ResultsStimulation at electric field amplitudes of 5–20 mV/mm at 10–20 Hz rapidly increased cerebral blood flow (within 100 ms), which then quickly decreased with no residual effects. The time to peak and blood flow shape varied with stimulation intensity and duration, showing a linear correlation between stimulation dose and peak blood flow increase. Neither afterdischarges nor spreading depression occurred from this level of stimulation. ConclusionsExtracranial stimulation amplitudes sufficient to evoke reliable blood flow changes require electric field strengths higher than what is tolerable in unanesthetized humans (<1 mV/mm), but less than electroconvulsive therapy levels (>40 mV/mm). However, anesthesia effects, spontaneous blood flow fluctuations, and sampling error may accentuate the apparent field strength needed for enhanced blood flow. The translation to a human dose–response function to augment cerebral blood flow (i.e., in stroke recovery) will require significant modification, potentially to pericranial, focused, multi-electrode application or intracranial stimulation.