Effect Of Nonuniform Electric Field Research Articles

Modeling of the effects of non-uniform electric field on resonant tunneling in superlattices

Modeling of the effects of non-uniform electric field on resonant tunneling in superlattices

Spectral characteristics on increasing hydrophilicity of Alfalfa seeds treated with alternating current corona discharge field.

In this study, corona discharge at atmospheric pressure under an alternating current (AC) field with a multi-needle plate electrode structure was used as mutagen to study the effects of corona discharge field on the hydrophilicity of alfalfa seeds, especially the effects of non-uniform electric field that is frequently ignored. Alfalfa seed were divided into two groups, one group was covered with 1mm-thick polypropylene petri dish cover that can be approximated as a single factor effect of non-uniform electric field, the other group was directly irradiated by corona discharge field under different parameters. Fourier transform infrared spectroscopy (FTIR) and dual-index sequence analysis were used to detect and compare the spectra of alfalfa seed coats with different treatments. Results showed that the peaks of the seed coat at 2856 and 1727cm-1 in the treatment group changed, indicating that hydrophobic wax, lipid, and cellulose may be cracked or degraded. Corona discharge field treatment can change the chemical structure of alfalfa seed coats, resulting in the changes in their hydrophilicity. The results of the apparent contact angle and scanning electron microscopy (SEM) and other experiments showed that the change in 19kV non-covered treatment group was greatest, the petri dish cover can effectively reduce the physicochemical etching of ionic wind, the hydrophilicity of alfalfa seeds improved after corona discharge field treatment regardless of whether there is an ionic effect during irradiation, and the ionic wind has a greater influence on the hydrophilicity of alfalfa seeds than the non-uniform electric field. This study revealed the biological effect mechanism of corona discharge field from the perspective of spectral characteristics and provided experimental data support for the analysis of alfalfa seed surface modification and chemical structure after corona discharge field treatment.

Semiclassical wave packet dynamics in nonuniform electric fields

We study the semi-classical theory of wave packet dynamics in crystalline solids extended to include the effects of a non-uniform electric field. In particular, we derive a correction to the semi-classical equations of motion (EOMs) for the dynamics of the wave packet center that depends on the gradient of the electric field and on the quantum metric (also called the Fubini-Study, Bures, or Bloch metric) on the Brillouin zone. We show that the physical origin of this term is a contribution to the total energy of the wave packet that depends on its electric quadrupole moment and on the electric field gradient. We also derive an equation relating the electric quadrupole moment of a sharply peaked wave packet to the quantum metric evaluated at the wave packet center in reciprocal space. Finally, we explore the physical consequences of this correction to the semi-classical EOMs. We show that in a metal with broken time-reversal and inversion symmetry, an electric field gradient can generate a longitudinal current which is linear in the electric field gradient, and which depends on the quantum metric at the Fermi surface. We then give two examples of concrete lattice models in which this effect occurs. Our results show that non-uniform electric fields can be used to probe the quantum geometry of the electronic bands in metals and open the door to further studies of the effects of non-uniform electric fields in solids.

Numerical analysis of non-uniform electric field effects on induced charge electrokinetics flow with application in micromixers

Induced charge electrokinetics (ICEK) has recently expanded its range of applications in biomedical engineering due to its high potential for being used in particle/cell manipulation platforms, micromixers, micropumps, and microvalves. In these devices, the generated microvortices around conducting hurdles/electrodes are used in order to achieve the desired operations. In the present study, the influences of non-uniform electric field on the generated microvortices around a conducting cylinder are analyzed in a micromixer. The electric field non-uniformities are produced either by pin-plate electrodes or by geometrical configuration. Results show that inhomogeneous electric fields lead to reduction of the induced zeta potential (IZP) and the microvortices velocity around the cylinder in the majority of the studied cases. However, imposing two electric fields with appropriate directions or positioning the cylinder in a suitable location enhances the IZP reductions. In this study, such electric fields are utilized in the ICEK micromixer for investigation of their effects on the mixing efficiency. Based on our findings, it is demonstrated that the generated electric field by two electrodes with angle of 30° increases the mixing efficiency from 69.07% to 96.89%. The present study provides new insights into the effects of non-uniform electric field on the IZP over a conducting hurdle and the generated microvortices in ICEK flows with an application in lab-on-a-chip (LOC) devices such as micromixers, microvalves, micropumps, and particle/cell separators.

Dielectrophoretic effect of nonuniform electric fields on the protoplast cell

In recent years, dielectrophoresis based microfluidics systems have been used to manipulate colloids, inert particles, and biological microparticles, such as red blood cells, white blood cells, platelets, cancer cells, bacteria, yeast, micro‌organisms, proteins, DNA, etc. In the current study the governing electric potential equations have been solved in the presence of cell for the purpose of studying particle-electric field dielectrophoretic interaction. Immersed Interface Method (IIM) which is a modified finite difference method is used to solve the governing 2D elliptic electrostatic equations with irregular boundaries. A neutral particle polarizes under the application of an electric field and causes local nonuniformity in electrostatic potential distribution. So cells experience electric stresses on its surface. The electric stress on cell surface is calculated by Maxwell Stress Tensor (MST) on both sides of cell. DEP force is calculated by integrating electric stress on particle surface. In the present study calculated electric stresses is validated by DEP force calculated using EDM method and exact solution. we neglect other electrokinetic effects such as electrophoresis and electro-osmosis. Electrophoresis can be neglected if the particles are not charged. The effect of applied voltage, dielectric constants of cells and cells orientation on particle-particle interaction force has been studied.

Effect of nonuniform electric field on the electrohydrodynamic motion of a drop in Poiseuille flow

The effect of a nonuniform electric field on the electrohydrodynamic motion of a leaky dielectric suspended drop in the presence of background Poiseuille flow is investigated analytically. Considering the nonuniform electric field to be a linear combination of uniform and quadrupole fields, the velocity of a force-free drop positioned at the flow centerline is obtained. The drop velocity is strongly influenced by the surface charge distribution and drop shape. In the Stokes flow limit, we employ an asymptotic method considering weak surface charge convection and small shape deformation. The present study shows the importance of type of nonuniform electric field (converging or diverging in the direction of the Poiseuille flow), strength of the electric field relative to the Poiseuille flow, and material property ratios on the magnitude and direction of drop motion in the presence of flow curvature. In the presence of a nonuniform electric field, the flow curvature can increase or decrease the drop velocity as compared with a uniform flow case. The converging electric field always drives a perfectly conducting drop in the direction of the Poiseuille flow with increased velocity, while the diverging electric field can drive the drop in either direction, depending on the relative strength of the applied electric field. Shape deformation increases the velocity of a perfectly conducting drop in the converging electric field, while shape deformation increases/decreases the velocity magnitude of a perfectly conducting drop in the diverging electric field. The converging electric field always drives a perfectly dielectric drop in the direction of the Poiseuille flow with increased (or decreased) velocity when the drop phase permittivity is greater (or less) than the medium phase permittivity. The diverging electric field can move a perfectly dielectric drop in either direction, depending on the strength of the electric field relative to the Poiseuille flow and drop-to-medium permittivity ratio. Shape deformation increases the velocity magnitude of a perfectly dielectric drop for larger permittivity ratios. For leaky dielectric drops, both surface convection and shape deformation can increase or decrease the drop velocity in nonuniform electric field, depending on the electrohydrodynamic properties of the drop and the suspending medium.

Thickness Dependence of Photovoltaic Effect in BiFeO3 Thin Films Based on Asymmetric Structures

BiFeO3 (BFO) thin films with different layers were deposited on Pt/Ti/SiO2/Si substrates via the sol–gel method, and the effect of nonuniform electric field formed by asymmetry electrodes on the photovoltaic properties has been investigated through experimental approaches. The Au/BFO/Pt heterostructures show 1.3 V open-circuit voltages and ∼0.242% photovoltaic power conversion efficiency when illuminated under sunlight (AM 1.5), this high efficiency is at least one order of magnitude larger than many other values thus far reported for BFO-based devices prepared by the spin coated method. The film layer dependence of the photovoltaic effect suggests that the large open-circuit voltage and high efficiency are contributed by both the ferroelectric polarization and the asymmetric structures formed by top and bottom electrodes. Theoretical analysis indicates that the efficiency may be further significantly improved by increasing the number of film layers and the nonuniform depolarization field, implying potential applications.

The Effects of Piezoelectric Ceramic Dissipation Factor on the Performance of Ultrasonic Transducers

The dissipation factor (DF) is an important material property of piezoceramics that governs the amount of self-heating under resonant conditions; it essentially quantifies a particular material type for either an actuator or resonator application: high DF materials with typically higher output (d33) are better for actuators, whereas low DF materials with typically lower d33 are better for resonators. Transducer designers must often compromise between mechanical output and DF in the selection of piezoceramics for power ultrasonic applications, and abnormally high DF is one of the main causes of production stoppages. In theory DF is simply the current/voltage phase deviation from an ideal capacitor at 90° (a.k.a. tan(δ) or dielectric loss). Abnormally high DF is typically caused by moisture absorption due to poor ceramic porosity, which causes voltage leakage effects; e.g., seen in transducer production when setting piezo stack preload. Corresponding large increases in capacitance can also be associated with poor porosity, which is counterintuitive unless there is moisture absorption or electrode wicking. This research investigates the mechanisms for abnormally high DF in peizoceramics, and its corresponding effect on transducer performance. It investigates if DF is only affected by the bulk dielectric properties of the piezoceramics (e.g. porosity), or is also influenced by non-uniform electric field effects from electrode wicking. It explores if higher DF ceramics can affect transducer displacement/current gain stability via moisture expulsion at higher drive levels. The investigation focuses solely on the common PZT8 piezoelectric material used with welding transducers for semiconductor wire bonding. Transducers are built with both normal DF peizoceramics, and those with abnormally high DF ceramics which caused production stoppages. Several metrics are investigated such as impedance, displacement gain and capacitance. The experimental and theoretical research methods include Bode plots, SEM cross-sections, Archimedes method, equivalent circuits, laser vibrometry and finite element analysis.

Effects of high electric field on low-velocity gas-solid two-phase flow movement

It is of significance to study the movement of solid - gas mixed flow of small particle size in the high electric field region for explaining such insulation accidents as contamination deposition, gap breakdown, unknown flashovers, and the like occurring on power line insulators surface. Based on artificial simulation experiments, we applied the particle image velocimetry (PIV) technology to investigate the flow-electric field coupling movement of low-speed mixed flow, comprehensively compare the effects of electric field uniformity, voltage levels, wind speed and other factors on the distribution of flow field. The results show that the effect of non-uniform electric field on the flow field is apparently stronger than that of uniform electric field. It increases with the applied electric field increasing, and decreases a little with the wind speed increasing. In the uniform electric field, the particles have a trend to move to the cathode plate, while in the non-uniform electric field, they are evidently charged under the action of corona and prone to moving toward the anode plate. In contrast, the effect of the AC electric field on the flow field is weaker than that of the DC electric field. However, it still has obvious manifestation. These relevant conclusions play an active role for in-depth research on the external insulation characteristics of HV power grid in sand dust environments such as pollution deposition and distribution on the surface of insulation string, breakdown of the air gap, etc., especially the charged mechanism of small sized dust and sand particles.

Effects of nonuniform electric field on slit flow of an electrorheological fluid

In this work, slit flow of an electrorheological (ER) fluid is studied via laser Doppler anemometry under nonuniform electric‐field conditions. For that purpose, the electrodes were coated with a PVC foil. Under ac conditions the ER effect with homogeneous coating was smaller than in the case of no coating. Yet, as soon as holes were punched in the foil, the ER effect greatly increased, exceeding the effect of the uncoated electrodes. Irrespective of the type of coating applied, the electric current remained the same. This contrasts with the results under dc conditions where (i) the ER effect with coating (irrespective of the type of coating) was smaller (or even zero) than without coating and where (ii) a decrease of the ER effect always was accompanied by a decrease in electric current. No electric current implied no ER effect, irrespective of the strength of the applied electric field.

Impurity photoionization in the presence of a static electric field: Phonon coupling and non-uniform electric field effects

The modifications induced by a static electric field (Franz-Keldysh effect and Franz-Keldysh oscillations) in the photoionization cross section of semiconductor impurities are studied in presence of two factors relevant to experimental measurements: the electron-phonon polar coupling and a linear spatial variation of the applied electric field. Important for II-VI and III-V semiconductors, the electron-phonon polar coupling is treated using an approach adapted from the classical work of Huang and Rhys. Our calculations show that the Franz-Keldysh oscillations should be visible even in the presence of the electron-phonon interaction for shallow impurities. For deeper impurities, the oscillations should be visible if the electron-phonon coupling is weak, which is unlikely to happen in II-VI semiconductors. We also show that a linear spatial variation of the applied electric field leads to modifications of much smaller amplitude.

Effect of non-uniform electric fields on convective heat transfer in a colloidal fluid

The effect of radial electric fields on the convective heat transfer coefficient of a colloidal fluid (haematite in distilled water) has been studied as a function of various quantities such as time, electric field, pH value, colloidal concentration and orientation. The electroconvective heat transfer coefficient exhibits a 'timing' effect as well as an 'aging' effect. Whereas an AC field always enhances the heat transfer, a DC field produces an enhancement that is almost vertical in the vicinity of the origin. An increase in particle concentration increases the heat transfer coefficient, while a sharp rise in heat transfer coefficient is observed when the surface charge of the collidal particle is increased. Furthermore, the convective heat transfer coefficient increases when the inclination of the cylinder is changed from the horizontal to the vertical position.

希ガスにおける不平等電界の放電開始電圧に及ぼす影響

希ガスにおける不平等電界の放電開始電圧に及ぼす影響

Electric field gradients and band sharpening in DNA gel electrophoresis.

A mathematical study of the effect of non-uniform electric fields on the width of DNA electrophoretic bands is presented. Using a simple model, we show that field gradients sharpen these bands during an experiment if the corresponding gradient of electrophoretic velocity is large enough. This is in agreement with experimental results indicating that narrower bands form when pulsed field electrophoresis is carried out in the presence of field gradients. Moreover, it is shown that there is in fact an optimal experimental duration that maximizes separation. Finally, gradients are also predicted to reduce the relative mobilities of the DNA fragments, which is a serious drawback of this technique.

Effects of non-uniform electric fields on the convergence behavior of energy expansions

The influence of electric field gradients on the radius of convergence of the energy expansion is investigated using an analysis based on N-variable rational approximation for the power series. The influence of the field gradient on the energy of LiH in a one-dimensional electric field is found to be greatest at small internuclear distances. The radius of convergence is smallest at large internuclear distances. The implications of these results for finite field and test charge calculations are discussed.

Effects of Non-Uniform Electric Fields on Vaporization

熱伝達と物質伝達の共存する相変化現象におよぼす電気流体力学的効果を解明するための,水の蒸発におよぼす不等電解の影響を取り上げ,まず,物質伝達率が水面の上に細線の陽極を置くことにより,電解をかけないときの10倍以上に増加することを実験的に示し,一方この原因はコロナ風の存在にあると考えて理論解析し,蒸発量の増加が定量的における液流のドライアウトが性能に大きな影響をもつことを知った.

Nonuniform electric field effects on zener tunneling in semiconductors

Expressions for Zener tunneling probability, which are based on a simple two-band theory and a nonuniform electric-field of the profile ε = ε 0 e −ax, are calculated explicitly. It is shown that the magnitude of tunneling probability increases as the penetration depth of the electric field decreases. Also numerical example for InSb is discussed.

Nonuniform Electric Field Effects in MHD Slider Bearing

Nonuniform Electric Field Effects in MHD Slider Bearing

Effect of non-uniform electric fields on drift instabilities

A general equation describing drift instabilities in a low beta plasma, in the presence of non-uniform electric fields perpendicular to the magnetic field, is derived using a guiding centre fluid picture for the ions and the drift kinetic equation with Krook-like collision term for the electrons. Both the collisionless and the collisional regime, and therefore also the transition between them, can thus be described starting from the same equation. The equation is discussed and the influence of the electric field studied in the framework of a local approximation.

The effect of nonuniform electric fields on Gunn oscillators

The effect of nonuniform electric fields on Gunn oscillators