Effects Of Electric Field Frequency Research Articles

Effect of external electric field on agglomeration characteristics of Cu nanoparticles: A molecular dynamics study

In order to study the effect of electric field on the stability of Cu nanoparticles in water, molecular dynamics method was used to simulate the agglomeration characteristics of Cu nanoparticles. The microscopic agglomeration characteristics of nanoparticles by electric field were analyzed using the distribution and collision of nanoparticles in water at different times, as well as the potential energy, kinetic energy, diffusion coefficient and radial distribution function of the system. The results show that the collision of Cu nanoparticles was inhibited in the presence of both uniform and alternation electric fields. The total potential energy of the system decreases with each collision of particles. When all of the particles are agglomerated, the total potential energy of the system remains constant. According to the radial distribution function, when the electric field intensity increases, the degree of aggregation of water molecules on the particle surface strengthens and then weakens as the electric field strength. Meanwhile, the degree of aggregation decreases with the increasing frequency of the alternating electric field. The effect of electric field frequency on the diffusion coefficient of nanofluid is insignificant. However, as the strength of the electric field increases the diffusion coefficient of the nanofluid decreases, while the resistance coefficient of water molecules increases, and the presence of the electric field inhibits the movement of water molecules. The influence of electric field on the heat transfer and deposition characteristics of nanofluids can be obtained by experiments, but the influence mechanism is difficult to be analyzed by experimental means. The molecular dynamics method also provides a new idea to reveal the influence mechanism of electric field.

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.

Ionic Chiral Ferrocene Doped Cholesteric Liquid Crystal with Electronically Tunable Reflective Bandwidth performance.

Cholesteric liquid crystals (CLC) were widely used in optical devices as one-dimensional photonic crystals. However, their reflective bands cannot be adjusted, which limits their wide application in many fields. In this paper, a series of ionic chiral ferrocene derivatives (CD-Fc+) as dopants were designed and prepared, and their doping into negative liquid crystal matrix was investigated to develop cholesteric response liquid crystal composites with electrically tunable reflective bands. The effects of electric field frequency, voltage, retention time of voltage and molecular structure on the broadening of reflection bandwidth were investigated in detail.

Study on the Performance of an Electric-Field-Enhanced Oil–Water Separator in Treating Heavy Oil with High Water Cut

As most offshore oilfields come to the middle- and late-exploitation period, and with the popularization of tertiary enhanced oil recovery (EOR) technology, the physical properties of produced fluids become more complex, bringing new challenges to oil-water separation. Conventional solutions, such as increasing the input of chemicals, enlarging the volume of the separator equipment, and extending the processing, are usually uneconomical and space-wasting. Electric-field-enhanced oil-water separation equipment was developed in this paper, and a mine field test was carried out. With the average water cut of different sampling ports and the overall dehydration rate taken as indicators, the effects of electric field frequency, inlet flow, chemical type, and addition upon the separation of the device were evaluated. The experimental results showed that for the ABJ mixed liquid, the optimal operating frequency of the electric field is above 3500 Hz. Compared with traditional separation equipment, the advantages of the electric-field-enhanced oil–water separation equipment are more significant in large flow conditions. When the water cut of the platform inlet fluctuates between 78% and 97%, and without the addition of chemicals, the average water cut was reduced to 7% and the average dehydration rate reached 90%, an improvement of about 15%.

Numerical simulation of droplet deformation in low frequency half-sinusoidal electric field

For investigating the influence of various parameters on the droplet deformation under the AC electric field condition, a simulation model for the droplet deformation in immiscible two fluids was established based on the phase field method. The distribution of flow field and electric field force are analyzed by simulation; the effects of electric field frequency, electric field intensity, droplet diameter, surface tension and continuous phase viscosity on the droplet deformation are simulated under the half-sinusoidal wave electric field condition. The simulation is performed in the low frequency half-sinusoidal waveform electric field. The simulation results show that the frequency of droplet oscillation is the same as that of the electric field. With the increase of electric field intensity and droplet diameter, the droplet deformation increases. However, the increase presents exponentially and linearly, respectively. Besides, the droplet deformation decreases exponentially with the surface tension increasing, and linearly with the continuous phase viscosity increasing. Under the condition of small deformation, there exists a linear relationship between the droplet maximum deformation and the Weber Number. More important, the influence of various factors on the deformation from strong to weak is electric field intensity, droplet diameter, surface tension, electric field frequency, continuous phase viscosity. And there is interaction between these factors. The simulation results provide theory evidence for the further research on electrostatic coalescence mechanism and the development of effective and compact electrostatic coalescence equipment.

Effect of input voltage frequency on the distribution of electrical stresses on the cell surface based on single-cell dielectrophoresis analysis

Electroporation is defined as cell membrane permeabilization under the application of electric fields. The mechanism of hydrophilic pore formation is not yet well understood. When cells are exposed to electric fields, electrical stresses act on their surfaces. These electrical stresses play a crucial role in cell membrane structural changes, which lead to cell permeabilization. These electrical stresses depend on the dielectric properties of the cell, buffer solution, and the applied electric field characteristics. In the current study, the effect of electric field frequency on the electrical stresses distribution on the cell surface and cell deformation is numerically and experimentally investigated. As previous studies were mostly focused on the effect of electric fields on a group of cells, the present study focused on the behavior of a single cell exposed to an electric field. To accomplish this, the effect of cells on electrostatic potential distribution and electric field must be considered. To do this, Fast immersed interface method (IIM) was used to discretize the governing quasi-electrostatic equations. Numerical results confirmed the accuracy of fast IIM in satisfying the internal electrical boundary conditions on the cell surface. Finally, experimental results showed the effect of applied electric field on cell deformation at different frequencies.

Effects of frequency on the electrical conductivity of whole shell egg components

AbstractIn an attempt to investigate ohmic heating of shell eggs, the electrical conductivity of its components was determined. Whole shell eggs were split up into five major components including yolk, thin albumen, thick albumen, membrane, and shell. Each was individually tested to determine the effects of electric field frequency and temperature on electrical conductivity. Electrical conductivity of the liquid egg components show results similar to literature values. In the range of frequencies from 10 to 100,000 Hz, little or no frequency dependence was noted for electrical conductivity, with temperature being a far more significant variable. A modeling study for ohmic heating of whole eggs showed significant disagreement with experiment, due principally to inaccuracy in measurement of shell conductivity—accuracy was improved when using an eggshell conductivity that was far lower than the measured value. Nevertheless, despite the lack of significant ohmic heating effects, some current flow within eggs was noted. While data for liquid components may be considered reliable, methods for measuring electrical conductivity of low‐moisture, solid components such as eggshells need to be improved.Practical ApplicationsWe show the effects of frequency on the electrical conductivities of various shell egg components, in particular including the shell and shell membrane, and verify the accuracy of properties data with a heat transfer model. This work is useful for egg industry applications due to recent concerns about contamination with Salmonella, which has prompted research into alternative methods of in‐shell pasteurization of eggs.

Effect of ohmic heating parameters on peroxidase inactivation, phenolic compounds degradation and color changes of sugarcane juice

The non-thermal effects of electricity on enzymatic inactivation kinetics of peroxidase (POD) and on phenolic compounds degradation during ohmic heating (OH) of sugarcane juice were investigated. Experiments with different frequencies (10–105Hz), waveforms (sine, square, triangle and pulsed waves) and voltage gradients (3.9 and 20.5V/cm) were conducted at 75°C for 25min and compared with the conventional treatment, performed with similar temperature histories. Overall, the results indicated that the non-thermal effects of OH (voltage gradient up to 20.5V/cm, with different frequencies and waveforms) did not influence the biochemical reactions that occur during POD inactivation in sugarcane juice. Moreover, there was no effect of electric field frequency or voltage gradient on phenolic compounds stability; on the other hand, some waveforms promoted higher degradation of these compounds. Some color changes were observed when 10Hz/25V and 60Hz/130V were applied, with higher magnitude at the higher electric field strength.

In-situ activity of α-amylase in the presence of controlled-frequency moderate electric fields

Studies on the effects of electric fields on enzymatic activity have typically focused on post-treatment residual activity. However, information on their effects on in-situ activity is scant. The objective of this study was to investigate the effect of controlled-frequency Moderate Electric Fields (MEF) on α-amylase activity. Relative α-amylase activities were measured in-situ in the presence of an electric field (1 V/cm, 1 Hz-1MHz) at 60 °C, with a zero electric field at the same temperature serving as a control treatment. Results show a significant nonthermal effect of electric field frequency on α-amylase activity, with up to 41% enhancement of the activity in the 1–60 Hz frequency window. At higher frequencies, activity was either unaffected, or slightly inhibited by the presence of the electric field. Molecular dynamics simulation results show that in the 1–60 Hz frequency window, the translational electrophoretic enzyme displacement approaches the intermolecular spacing of water. Interestingly, enzyme rotational motion transitions from oscillatory behavior to full rotation below 60 Hz. Application of higher frequencies restricts the electrophoretic displacement of the enzyme due to rapid reversal of the direction of the electric field.

Influence of Electric Field Frequency on the Process of Destruction of Water-Oil Emulsions in Electric Dehydrators

The effect of electric field frequency on the processes of destruction of water-oil emulsions in electric dehydrators is investigated. It is shown that the existing theoretical concepts regarding the processes of deformation, destruction, coagulation, and coalescence of droplets, and data available in the literature should be considered for three characteristic cases of an electric field being applied to the emulsion: a constant electric field; an alternating electric field with a frequency below the critical value; an alternating electric field with a frequency above the critical value. It is concluded that the effect of electric field frequency on the process of destruction of industrial water-oil emulsions in electric dehydrators is most pronounced under the influence of an alternating electric field with a frequency below the critical value in the working zone of the electric dehydrator, which has the shape of a confuser or a channel with a constant cross section.

Effect of Electric Field Frequency on the AC Electrical Treeing Phenomena in an Epoxy/Reactive Diluent/Layered Silicate Nanocomposite

The effects of electric field frequency on the ac electrical treeing phenomena in an epoxy/reactive diluent/layered silicate (1.5 wt%) were carried out, in needle-plate electrode arrangement. A layered silicate was exfoliated in an epoxy base resin, by using our ac electric field apparatus. To measure the treeing propagation rate, constant alternating current (AC) of 10 kV with three different electric field frequencies (60, 500 and 1,000 Hz) was applied to the specimen, in needle-plate electrode arrangement, at 30℃ of insulating oil bath. As the electric field frequency increased, the treeing propagation rate increased. At 500 Hz, the treeing propagation rate of the epoxy/PG/nanosilicate system was0.41×10-3 mm/min, which was 3.4 times slower than that of the epoxy/PG system. The electrical treeing morphology was dense bush type at 60 Hz; however, as the frequency increased, the bush type was changed to branch type, having few branches, with very slow propagation rate.

Effect of Electric Field Frequency on the AC Electrical Treeing Phenomena in an Epoxy/Layered Silicate Nanocomposite

The effects of electric field frequency on the AC electrical treeing phenomena in an epoxy/layered silicate (1.5 wt%) were investigated in a needle-plate electrode arrangement. A layered silicate was exfoliated in an epoxy-base resin with AC electric field apparatus. To measure the treeing initiation and propagation- and the breakdown rate, a constant alternating current (AC) of 10 kV with three different electric field frequencies (60, 500, and 1,000 Hz) was applied to the specimen in the needle-plate electrode specimen in an insulating oil bath at . At 60 Hz, the treeing initiation time was 12 min, the propagation rate was mm/min, and the morphology was a dense branch type. As the electric field frequency increased, the treeing initiation time decreased and the propagation rate increased. At 1,000 Hz, the treeing initiation time was 5 min, the propagation rate was mm/min, and the morphology was a dense bush type.

Ascorbic acid degradation and color changes in acerola pulp during ohmic heating: Effect of electric field frequency

The effect of the electric field frequency on ascorbic acid degradation and color changes in acerola pulp during ohmic heating was evaluated and this technology was compared with the conventional heating process. The electric field frequency was evaluated in the range between 10 and 105Hz. The use of low electric field frequency (10Hz) led to greater ascorbic acid degradation and higher color changes probably due to the occurrence of electrochemical reactions. Above 100Hz these reactions were minimized and, as a result, ohmic and conventional heating processes showed similar degradation rates of ascorbic acid and similar color changes. The use of high electric field frequency did not affect the degradation kinetics of ascorbic acid and pigment compounds. This indicates that the ascorbic acid molecule predisposition for hydrogen donation in redox reactions was not affected by the rapidly varying electric field.

Stress- and temperature-dependent scaling behavior of dynamic hysteresis in soft PZT bulk ceramics

Effects of electric field-frequency, electric field-amplitude, mechanical stress, and temperature on the hysteresis area, especially the scaling form, were investigated in soft lead zirconate titanate (PZT) bulk ceramics. The hysteresis area was found to depend on the frequency and field-amplitude with the same set of exponents as the power-law scaling for both with and without stresses. The inclusion of stresses into the power-law was obtained in the form of which indicates the difference in energy dissipation between the under-stress and stress-free conditions. The power-law temperature scaling relations were obtained for hysteresis area ⟨A⟩ and remanent polarization Pr, while the coercivity EC was found to scale linearly with temperature T. The three temperature scaling relations were also field-dependent. At fixed field amplitude E0, the scaling relations take the forms of , Pr ∝T−1.2322 and (EC0 - EC) ∝T.

Scaling Behavior of Dynamic Ferroelectric Hysteresis in Soft PZT Ceramic: Stress Dependence

Effects of electric field-frequency, electric field-amplitude, and mechanical stress on the hysteresis area were investigated on soft PZT ceramic. At stress-free condition, the investigation found the area scales with frequency and field-amplitude in power-law form, ⟨A⟩ ∝ ƒ−0.25 E 0; however, with different set of exponents in comparing to those in the investigation on thin films structure. On the other hand, with compressive stresses turning on, the same set of the exponents with the stress-free condition is found to confirm universality. In addition, the scaling form of the area to triple parameters; i.e., frequency, field-amplitude, and stress in a power law form, ⟨A⟩ − ⟨A σ = 0⟩ = ⟨ A − A σ = 0⟩ ∝ ƒ− 0.25 E 0 σ 0.44 , was obtained.

Excitation of electric discharges (light emission) at the Rochelle salt surface by electric fields with low and high frequencies

The effects of electric field frequency on the temperature dependences of the light intensity I(T) emitted by electric discharges at the surface of Rochelle salt (RS) crystals were investigated. It is proved that the character of the I(T) curves registered for the low frequency electric field (0.02–15 kHz) is different than that observed at high frequency (300–350 kHz). Surface electric discharges induced by the low frequency (audiofrequency) electric field are generated mainly during the polarization reversal, whereas those excited at the high frequency (low radiofrequency) are essentially the yield of the piezoelectric resonance frequency of the crystals.