Increase Of Electric Field Intensity Research Articles

The tool electrode investigation of electrostatic field-induced electrolyte jet (E-jet) electrical discharge machining

This investigation addresses concerns in micro-electrical discharge machining (EDM) such as high tool electrode preparation cost, tool electrode wear, and tool electrode compensation by proposing a new electrostatic field-induced electrolyte jet tool electrode. This method utilizes the theory that in a strong direct current electric field, the electrolyte at the capillary tube outlet can form a Taylor cone based on the balance of electric field force and surface tension. Coupled with the increase of electric field intensity, a very fine jet can eject from the tip of the Taylor cone, and this induced charge on the tip leads to a discharge to the workpiece which can remove debris from the workpiece surface. After the discharge, the induced charge at the tip is neutralized, leading to the surface tension outweighing the electric field force and the withdrawal of the fine jet. As a result, the cyclic pulse discharge process is generated. During the process, the tip of the fine jet serves as the tool electrode. This paper identifies this cyclic pulse electrolyte jet tool electrode generation and discharge process in action and tests the machining ability of this tool electrode on a silicon wafer. This electrolyte jet tool is also shown to have no wear or compensation issues, and the cost compared to conventional EDM is shown to be small.

Structural properties and digestibility of pulsed electric field treated waxy rice starch

Waxy rice starch was subjected to pulsed electric field (PEF) treatment at intensity of 30, 40 and 50kVcm−1. The impact of PEF treatment on the granular morphology, molecular weight, semi-crystalline structure, thermal properties, and digestibility were investigated. The micrographs suggested that electric energy could act on the granule structure of starch granule, especially at high intensity of 50kVcm−1. Gelatinization onset temperature, peak temperature, conclusion temperature and enthalpy value of PEF treated starches were lower than that of native starch. The 9nm lamellar peak of PEF treated starches decreased as revealed by small angle X-ray scattering. The relative crystallinity of treated starches decreased as the increase of electric field intensity. Increased rapidly digestible starch level and decreased slowly digestible starch level was found on PEF treated starches. These results would imply that PEF treatment induced structural changes in waxy rice starch significantly affected its digestibility.

에틸렌 처리를 위한 충진층 유전체배리어방전 플라즈마 반응기의 특성

This work investigated the characteristics of a packed-bed plasma reactor system and the performances of the plasma reactors connected in series or in parallel for the decomposition of ethylene. Before the discharge ignition, the effective capacitance of the γ-alumina packed-bed plasma reactor was larger than that of the reactor without any packing, but after the ignition the effective capacitance was similar to each other, regardless of the packing. The energy of electrons created by plasma depends mainly on the electric field intensity, and was not significantly affected by the gas composition in the range of 0~20% (v/v) oxygen (nitrogen : 80~100% (v/v)). Among the various reactive species generated by plasma, ground-state atomic oxygen and ozone are understood to be primarily involved in oxidation reactions, and as the electric field intensity increases, the amount of ground-state atomic oxygen relatively decreases while that of nitrogen atom increases. Even though there are many parameters affecting the performance of the plasma reactor such as a voltage, discharge power, gas flow rate and residence time, all parameters can be integrated into a single parameter, namely, specific input energy (SIE). It was experimentally confirmed that the performances of the plasma reactors connected in series or in parallel could be treated as a function of SIE alone, which simplifies the scale-up design procedure. Besides, the ethylene decomposition results can be predicted by the calculation using the rate constant expressed as a function of SIE.

Effect of the direct current electric field on the initial corrosion of steel in simulated industrial atmospheric environment

The effects of the direct current (DC) electric field on the initial corrosion of steel in simulated solution were investigated using measurements of weight loss and polarization curves, XRD and SEM techniques. The major constituents of the corrosion products are α- and γ-FeOOH in SO42− solution. It was found that the corrosion rate of steel increased with the increase of DC electric field intensity. And the DC electric field suppresses the growth of α-FeOOH and the transformation of γ-FeOOH to α-FeOOH. All these lead to the reduction of the protective ability of rust layer and accelerate further corrosion of steel.

Electrospinning of polyacrylonitrile nanofibers using strain-hardening spinning solutions

The electrospinning of polyacrylonitrile (PAN) fibers from strain-hardening PAN solutions was studied. The strain-hardening PAN electrospinning solutions were prepared by adding ultrahigh-molecular-weight PAN (UHMWPAN) into medium-molecular-weight PAN (MMWPAN) solutions. The strain-hardening behavior of the solutions was evidenced by the CaBER extensional rheological tests. In electrospinning of PAN nanofibers, the solutions containing UHMWPAN were found to be stable when large electric field intensity was applied at a constant source-target distance, different from the case that a solution without UHMWPAN was used. PAN nanofibers with smaller diameter (270 nm compared with 496 nm for the nanofibers containing no UHMWPAN) could be electrospun from the strain-hardening solutions at larger electric field intensity and no beaded fibers were observed. The results of X-ray diffraction (XRD) and mechanical tests showed that the crystallinity, crystal orientation and mechanical performance of electrospun PAN nanofibers were improved with the increase of electric field intensity.

Variation of Two-Photon Absorption Cross Sections and Optical Limiting of Compounds Induced by Static Electric Field

By numerically solving the Maxwell-Bloch equations using an iterative predictor-corrector finite-difference time-domain technique, we investigate propagating properties of a few-cycle laser pulse in a 4,4′-bis(di-n-butylamino) stilbene (BDBAS) molecular medium when a static electric field exists. Dynamical two-photon absorption (TPA) cross sections are obtained and optical limiting (OL) behavior is displayed. The results show that when the static electric field intensity increases, the dynamical TPA cross section is enhanced and the OL behavior is improved. Moreover, both even- and odd-order harmonic spectral components are generated with existence of the static electric field because it breaks the inversion symmetry of the BDBAS molecule. This work provides a method to modulate the nonlinear optical properties of the BDBAS compounds.

Temporal instability of coflowing liquid-gas jets under an electric field

Temporal instability of an electrified liquid jet in the core of a high-speed gas stream is studied to better understand the electro-flow focusing (EFF) technique. Two types of physical models with and without viscosities of fluids are considered. One utilizes uniform basic flow and an axial electric field, while the other one considers both the axial and radial electric fields and employs appropriate velocity profiles based on the pipe flow for inner liquid and the error function for outer gas stream. Both models demonstrate that the axisymmetric instability and the helical instability are two most unstable modes in the EFF problem. The significance of free charge initially imposed on the interface is highlighted and the effects of surface tension and liquid viscosity on the jet instability are also studied. It is shown that the increase of free charge density can definitely promote both the axisymmetric and helical instabilities and the transition between them arises for sufficiently large free charge densities when the axial electric field intensity increases. Finally, the EFF experiments are carried out to compare with theoretical predictions in the temporal instability analysis and a good agreement between them is achieved.

Effect of electric field on thermal performance of thermosyphon heat pipes using nanofluids

In the present study the effect of electric field on thermal performance of two-phase closed thermosyphon as external modifications has experimentally investigated. Internal modifications applied by using two different water based nanofluids as working fluids. Nanofluids prepared by adding Al2O3 and CuO nanoparticles into the pure water using ultrasonic vibration system without adding any dispersant or stabilizer to prevent any possible change of chemical properties of the nanofluid. Results show that the thermal performance, and the Nusselt number ratio of thermosyphon gradually increase by increase in electric field intensity and nanofluids concentration. These values decrease by increasing in input power. Results also show that Al2O3/water nanofluid improves thermal performance of thermosyphon more than CuO/water nanofluid. Also, the experimental results indicate that the effect of nanoparticles on thermosyphon thermal performance is higher than the electric field. Maximum enhancement of Nusselt number ratio is about 43% that observed at 60W input power and 2.5% by volume of Al2O3 nanoparticles in the work fluid under 20V electrical field strength. Enhancement value is 39% for CuO/water nanofluid.

Effect of electric field intensity on the morphology of magnetic-field-assisted electrospinning PVP nanofibers

Polyvinylpyrrolidone (PVP) nanofibers were processed by magnetic-field-assisted electrospinning (MFAES) technique. Since electric field intensity was one of the most important parameters influencing fiber morphology, the research aimed to study how electric field intensity affects fiber morphology in MFAES technique. The experimental results revealed that the distribution of diameter widened while the average diameter of PVP fibers decreased and the degree of the alignment reduced with the increase of electric field intensity. However, the fibers would be conglutinated together when the electric field intensity was too low. Also, the increase of working distance made the average diameter and the degree of the alignment increase slightly under the same electric field intensity, but the fibers could be partially curved instead of being fully straight if the working distance was too long. It was also indicated that maintaining the electric field intensity at 1 kV/cm with the voltage-distance combinations of 12 kV-12 cm (for 12wt% PVP) and 15 kV-15 cm (for 14wt% PVP) among all other combinations would result in the optimal alignment as well as a narrow size distribution of the fibers.

Effect of Pulsed Electric Fields on the Antibacterial Activity of Ovotransferrin and Mechanism of Action

Ovotransferrin (OVT) is an iron-binding glycoprotein, found in egg white and serum. It appears to be a multi-functional protein with a major role in avian natural immunity and antimicrobial activity. In this study, the effects of high-intensity pulsed electric fields (HIPEF) on antibacterial activity of OVT particularly for Escherichia coli and the changes in its iron-binding capacity were investigated. Fluorescence spectra technology was used to analyze possible structural changes of OVT, explaining and exploring the effects of the HIPEF technology on the mechanisms that determine the protein activity. The results showed that when the electrical field intensity was 40 kV.cm-1, the antibacterial activity of OVT solution was the highest 87.9% as compared to the control (6.052×107CFU.mL-1) and iron-binding capacity reached the maximum 0.733, which was 2.4 times higher as compared to the control. When the pulse number reached at 80, the antibacterial activity of OVT solution increased up to 74.5% as compared to the control (6.052×107CFU.ml-1) and iron-binding capacity was 1.9 times higher than that of control. With the change of pH values from 7.0 to 8.0, the iron-binding capacity was slightly decreased, the difference was not significant among the groups (P>0.05). Fluorescence spectra analysis showed that the microenvironment of OVT changed with the increase of the pulsed electric field intensity and number and changes in the fluorescence intensity were measured constantly with fluroescensce quench phenomena occurring. The fluorescence intensity was reduced to minimum at 40 kV.cm-1or 80 pulse number. The results showed that the changes of the iron-binding capacity after HIPEF treatment were strongly linked with the changes of the antibacterial activity. An increase of the electrical field intensity and change in treatment time induced higher inhibition of Escherichia coli with OVT.

Tunable Microwave Frequency Performance of Nanocomposite Co<SUB>2</SUB>MnSi/PZN-PT Magnetoelectric Coupling Structure

Nanocrystalline Co2MnSi Heusler alloy films were deposited on the PZN-PT substrates by a composition gradient sputtering method. It is revealed that this multiferroic heterostructure shows very strong magnetoelectric coupling, leading to continuously tunable microwave frequency characteristics by electric field. With the increase of electric field intensity from 0 to 6 kV/cm, the magnetic anisotropy field H(K) increases from 90 Oe to 182 Oe with an increment of 102%, corresponding to a ME coefficient of 15.3 Oe cm/kV; the ferromagnetic resonance frequency f(FMR) shifts from 3.38 to 4.82 GHz with an increment of deltaf(FMR) = 1440 MHz or deltaf(FMR)/f(FMR) = 43%; moreover, the damping constant alpha dramatically decreases from 0.035 to 0.018. These merits demonstrate that this nanocomposite multiferroic structure is promising in fabrication of tunable microwave components.

Effects of external electric field on the excitation properties of anthracene molecule

The theoretical investigations on the molecular energy levels, energy gaps, and the singlet-singlet electronic excitation properties (such as absorption spectra, excited energy, oscillator strengths) of the anthracene molecule in different external electric field were carried out by employing density functional theory (DFT) and time-dependent density functional theory (TDDFT) method with 6-311G(d, p) basis set. The stable molecular structure in ground state was optimized by DFT. The calculated results show that the absorption bands of anthracene molecule concentrate in ultraviolet region without external electric field, the absorption peak of which corresponds to the S0→S5 transitions with an excitation wavelength of 234.5 nm. The calculated absorption spectra agree well with the experimental data. Moreover, it is noticeable that the effects of the external electric field on optical properties cannot be neglected. The ultraviolet absorption spectra of anthracene molecule show a red shift into the blue-light region with the increases of electric field intensity. At the same time, the energy gaps between LUMO and HOMO for the anthracene molecule decrease with the increase of external electric field intensity. It can be shown that the anthracene molecule is promising as a useful blue-light emitting material through modulating by an electric field.

Enhancement of ultrafiltration with a γ-Al2O3 ceramic membrane by an electrical field

Membrane fouling and concentration polarization are two of the main barriers for the application of the membrane separation technique in food industry. In order to increase membrane separation efficiency caused by membrane fouling and concentration polarization, γ-Al2O3 membrane was employed to separate bovine serum albumin (BSA) solution in the presence of an electrical field. In this paper, the influences of electric field intensity, pH of bulk solution, and operating time on membrane performance were investigated. It was found that the influence of an external electric field on the membrane process depends on the charged properties of bulk solution. For negatively charged BSA in the solution of pH 6.8, an external electric field can improve both the flux and rejection of membrane. What is more, separation process can be maintained at a quite high flux for 60 min without significant decrease in this method, and the increase of electric field intensity can improve the membrane separation efficiency. By analyzing transport resistance coefficient of membrane process, it was showed that application of electric field can sharply reduce boundary layer resistance Rb1, membrane fouling resistance Rf, and total resistance Rt. These results indicated that an electric field can decrease the concentration polarization and membrane fouling on the membrane surface, which contribute to the improvement of membrane separation efficiency.

Physicochemical properties of sugar beet pulp pectin by pulsed electric field treatment

SummaryThis research focused on pulsed electric field (PEF) modification of pectin from sugar beet pulp. Experimental parameters including electric field intensity (18–30 kV cm−1) and pulse time (806–2418 μs) were used, and the physicochemical properties of PEF‐treated pectin were evaluated by various instrumental techniques such as scanning electron microscopy, X‐ray diffraction, dynamic light scattering and Fourier transform infrared spectroscopy. The results showed that the degree of esterification, viscosity average molecular weight and particle size of pectin decreased with the increase in electric field intensity and pulse time. Meanwhile, some sharp interstices were shown on the surface of pectin, and its crystalline regions were destroyed after being treated with PEF. Results revealed that PEF technology is an effective method to obtain low‐molecular‐weight pectin with different degrees of esterification and obtain a desired production in food application.

Effect of pulsed electric field on the rheological and colour properties of soy milk

The effects of pulsed electric field (PEF) treatments on rheological and colour properties of soy milk were evaluated. Flow behaviour, viscosity and rheological parameters of PEF-treated soy milk were monitored using a controlled stress rheometer. For PEF treatments, electric field intensity of 18, 20 and 22 kV cm− 1 and number of pulses of 25, 50, 75 and 100 were used. For the measurements of rheological properties of soy milk shear rates between 0 and 200 s− 1 was used. The rheological behaviour of control and the PEF-treated soy milk were described using a power law model. The PEF treatments affected the rheological properties of soy milk. Apparent viscosity of soy milk increased from 6.62 to 7.46 (10− 3 Pa s) with increase in electric field intensity from 18 to 22 kV cm− 1 and increase in the number of pulses from 0 to 100. The consistency index (K) of soy milk also changed with PEF treatments. Lightness (L*), red/greenness (a*) and yellowness/blueness (b*) of soy milk were affected by PEF treatments.

Spiking patterns of a hippocampus model in electric fields

We develop a model of CA3 neurons embedded in a resistive array to mimic the effects of electric fields from a new perspective. Effects of DC and sinusoidal electric fields on firing patterns in CA3 neurons are investigated in this study. The firing patterns can be switched from no firing pattern to burst or from burst to fast periodic firing pattern with the increase of DC electric field intensity. It is also found that the firing activities are sensitive to the frequency and amplitude of the sinusoidal electric field. Different phase-locking states and chaotic firing regions are observed in the parameter space of frequency and amplitude. These findings are qualitatively in accordance with the results of relevant experimental and numerical studies. It is implied that the external or endogenous electric field can modulate the neural code in the brain. Furthermore, it is helpful to develop control strategies based on electric fields to control neural diseases such as epilepsy.

Effect of Pulse Electric Field on the Columnar Crystals Growth of Al-5.6 Wt.%Cu during Unidirectional Solidification

The influence of pulse electric field on the columnar crystals growth has been studied by employing pulse electric field vertically to the solid/liquid interface during unidirectional solidification. The results showed that the pulse electric field was favorable to columnar crystals growth with the increase of pulse electric field intensity when the liquid phase was the positive electrode of pulse electric field. The formation of equiaxed crystal was accelerated when the degree of composition supercooling in front edge of solid/liquid interface reached the degree of nucleation supercooling by pulse electric field. When the liquid phase was the negative electrode of pulse electric field, the growth of columnar crystals was hindered, and the formation of equiaxed crystal was accelerated by pulse electric field.

Optical nanofocusing by tapering coupled photonic-plasmonic waveguides

We have numerically designed a compact structure to concentrate optical waves from a silicon-on-insulator waveguide to a deep sub-wavelength and high intensity surface plasmon focal spot at the tip of a metallic strip taper. A systematic design approach is developed to obtain an optimal photon-surface plasmon side coupling efficiency of up to 50% at 1.55 μm wavelength, and an over 50 times increase in electric field intensity in a focal region of around 20nm × 20nm × 7nm in size. The length of the whole device is 2.2 μm. We expect fabrication of the proposed device to be simpler than devices in previous work.

The Effect of the Electric Field on Lag Phase, β-Galactosidase Production and Plasmid Stability of a Recombinant Saccharomyces cerevisiae Strain Growing on Lactose

Ethanol and β-galactosidase production from cheese whey may significantly contribute to minimise environmental problems while producing value from low-cost raw materials. In this work, the recombinant Saccharomyces cerevisiae NCYC869-A3/pVK1.1 flocculent strain expressing the lacA gene (coding for β-galactosidase) of Aspergillus niger under ADHI promoter and terminator was used. This strain shows high ethanol and β-galactosidase productivities when grown on lactose. Batch cultures were performed using SSlactose medium with 50 g L−1 lactose in a 2-L bioreactor under aerobic and microaerophilic conditions. Temperature was maintained at 30 °C and pH 4.0. In order to determine the effect of an electric field in the fermentation profile, titanium electrodes were placed inside the bioreactor and different electric field values (from 0.5 to 2 V cm−1) were applied. For all experiments, β-galactosidase activity, biomass, protein, lactose, glucose, galactose and ethanol concentrations were measured. Finally, lag phase duration and specific growth rate were calculated. Significant changes in lag phase duration and biomass yield were found when using 2 V cm−1. Results show that the electric field enhances the early stages of fermentation kinetics, thus indicating that its application may improve industrial fermentations’ productivity. The increase in electric field intensity led to plasmid instability thus decreasing β-galactosidase production.

Experimental study and theoretical analysis on the effect of electric field on gas explosion and its propagation

The effect of the electric field with different intensity on explosion wave pressure and flame propagation velocity of gas explosion was experimentally studied, and the effect of electric field on gas explosion and its propagation was theoretically analyzed from heat transportation, mass transportation, and reaction process of gas explosion. The results show that the electric field can affect gas explosion by enhancing explosion intensity and explosion pressure, thus increasing flame velocity. The electric field can offer energy to the gas explosion reaction; the effect of the electric field on gas explosion increases with the increase of electric field intensity. The electric field can increase mass transfer action, heat transfer action, convection effects, diffusion coefficient, and the reaction system entropy, which make the turbulence of gas explosion in electric field increase; therefore, the electric field can improve flame combustion velocity and flame propagation velocity, release more energy, increase shock wave energy, and then promote the gas explosion and its propagation.