Increase In Electric Field Strength Research Articles

Theory of electric field effect on the optical properties of elliptical quantum wire

In the approximation of the effective mass, the electric field effect on the optical properties of the elliptical quantum wire (EQW) was investigated. In an elliptic coordinate system, exact solutions of the Schrödinger equation for an electron in an EQW with hard walls are obtained. The electron energy spectrum consists of even and odd energies states, whose wave functions are expressed through even and odd Mathieu functions of the first kind. Using these solutions, an orthonormal basis was constructed. The influence of the electric field perpendicular to the quantum wire and parallel to the ellipse’s major axis on the energies and oscillator strength of quantum electron transitions was calculated using the matrix method. It is shown that the ellipticity of the quantum wire leads to the removal of the degeneracy of the energy spectrum of quasiparticles since the energies of even and odd electronic states depend differently on the ratio of the EQW semi-axes. The electron’s ground state is the even state, which is nondegenerate because there is no corresponding odd state. The electric field has a greater effect on energy states with a lower value of the magnetic quantum number. As the electric field strength increases, the energies of even and odd states shift to the region of lower energies.

An ab initio molecular dynamics investigation of the behaviour of amorphous substances in anodic aluminium oxide under electric field

In order to elucidate the diffusion behaviour of ions in alumina during the anodic alumina process, the effects of electric field strength, hydration content, and electrolyte on amorphous alumina and hydrated alumina were studied using ab initio molecular dynamics. The results show that the diffusion rate of ions in alumina increases with the increase in electric field strength, but there is an extreme value. The maximum diffusion rate of Al ions in alumina monohydrate is 21.8 μm2/ms/V, while in alumina trihydrate, it is 16.7 μm2/ms/V. The ionic diffusion rate of hydrated alumina is one to two orders of magnitude larger than that of anhydrous amorphous alumina due to the effect of the drag of H ions, which reduces the migration activation energy. Electrolytes also affect the diffusion rate of alumina through the action of H ions. The increase in H ions will not only enhance the diffusion rate of hydrated alumina but also render the hydrous compound more vulnerable to breakdown.

Particle-in-cell/Monte Carlo collision simulation on gap breakdown characteristics of under the conditions of hot-electrode and high-temperature gas medium in low-voltage circuit breaker chamber

The gas composition inside the low-voltage circuit breaker (LVCB) chamber and the residual plasma in the post-arc stage affect the breakdown process, which in turn affects the breaking capacity of LVCBs. In this paper, the back-arc breakdown and post-arc re-breakdown phenomena occurring inside the LVCB chamber are categorized as the breakdown in the case of high-temperature gas gap of hot electrodes, for which a particle-in-cell/Monte Carlo collision simulation model has been established, which takes into account the effects of high-temperature gas components, cathode electron thermal emission, electron collision ionization, and other effects, and simulation studies have been conducted. The simulation results show that the gap breakdown is mainly caused by the high-temperature hot free background gas and the cathode thermal electron emission. A plasma sheath layer is formed at the cathode during the breakdown process, and the electric field strength in the sheath layer is higher than that in other regions. With the development of the streamer to the cathode, the thickness of the sheath layer becomes narrower and the electric field strength increases, and finally, a discharge plasma channel is formed in the gap.

Characterizing the electric field- and rate-dependent hysteresis of piezoelectric ceramics shear motion with the Bouc-Wen model

Piezoelectric technology is widely used in the field of precision drives. However, when piezoelectric actuators are employed at high voltages and high frequencies, their hysteresis can greatly affect the accuracy of such systems. The Bouc-Wen model has typically been used by researchers to characterise the hysteresis of piezoelectric materials. Besides, to extract the parameters of this model from experimental data, particle swarm optimization (PSO) is often employed. However, the majority of such studies only considers hysteresis as a function of the electric field strength and not as a function of actuation frequency. In addition, most of such existing reports have focused on longitudinal type piezo actuators. In this context, the research presented here complements this body of knowledge by demonstrating the application of the PSO algorithm for determining the parameters of the Bouc-Wen model when hysteresis depends not only on the electric field but also on the rate of the driving signal and when applied on a shear-type piezoelectric actuator. The obtained experimental data showed that with the increase of electric field strength, both the piezoelectric coefficient and hysteresis value increased significantly, and that with the increase of frequency, the piezoelectric coefficient decreased, while the hysteresis value changed slightly. The variations of the Bouc-Wen model parameters with the electric field and frequency were identified and then used to predict the shear motion trajectory of the piezoelectric stack. It was found that in the identified range of electric field and frequency, the predicted error rate of the hysteresis loop amplitude was less than 16.5% with a minimum value of 0.1%, and the error rate of the hysteresis loop width was less than 14.5% with a minimum value of 2.7%. Based on the identified electric field- and rate-dependent Bouc-Wen model, a novel finite element (FE) model was also proposed to analyse the effect of electrical and mechanical coupling on the piezoelectric movement.

Optimizing chaotic frequency electric fields for deformation analysis of droplets based on numerical modeling

Chaotic pulse group (CPG) electric field has already been proposed to achieve demulsification of water-in-oil (W/O) emulsions; however, the electric field parameters of the CPG electric field for efficient demulsification of emulsions are unknown. Therefore, in this study, the numerical model of droplet deformation under the action of electric field was established by coupling the flow field and electric field, and the effectiveness of the model was verified by comparing with the experimental results. In the numerical model, the electric field parameters are optimized by droplet deformation; moreover, the influence of surface tension and oil viscosity on the optimal electric field parameters is discussed; the deformation of droplets under the optimized CPG electric field was analyzed. The results show that when the droplet radius is 1 mm, the optimal electric field strength is 612 kV/m, the optimal pulse width is 0.023 s, and the optimal pulse rest width is 0.017 s. The increase in interfacial tension leads to the increase in optimal electric field strength, and the decrease in optimal pulse width and pulse rest width. The increase in oil viscosity leads to an increase in the optimal electric field parameters. With the increase in interfacial tension and oil viscosity, their influence on the deformation of droplets gradually decreases. Droplets of different sizes could find their own optimal electric field parameters in the CPG electric field, so as to achieve the maximum deformation. The results provide valuable guidance for the selection of electric field parameters in CPG electric field industrial applications.

Electrohydrodynamic capillary instability of Rivlin–Ericksen viscoelastic fluid film with mass and heat transfer

AbstractThis paper presents an analysis of viscous fluids and a Rivlin–Ericksen (R‐E) viscoelastic fluid interface under the influence of heat and mass transfer, while both fluids are exposed to an axial electric field. The fluids are restricted within an annular region that is enclosed by two rigid cylinders. The outer section of the annular region holds the R‐E viscoelastic fluid, while the inner section is filled with the viscous fluid. To ascertain the correlation between perturbation growth and wavenumber, the theory of potential flow on viscoelastic–viscous fluids is applied, and the result is represented as a second‐order polynomial. This correlation is numerically solved using the Newton–Raphson method. Variables of viscous flow, such as electric field strength, heat transfer coefficient, viscoelasticity, viscosity, and so forth, are numerically studied. With an increase in electric field strength, the perturbation growth decays and expands for the particular combinations of permittivity and conductivity ratio, showing the dual effect of the axial electric field.

Electric field as a crystallization switch of heterogeneous ice formation

Using molecular dynamics simulations, we investigated the effect of external electric field on ice formation with the present of a substrate surface. It turns out that the electric field can affect the ice formation on substrate surface by altering the dipole orientation of interfacial water molecules (IWs): a crossover from inhibiting to promoting ice formation with the increase of electric field strength. According to the influence of the electric field on ice formation, the electric field strength range of 0.0 V nm−1–7.0 V nm−1 can be divided into three regions. In the region I and region III, there are both ice formation on the substrate surface. While, the behavior of IWs in the region I and region III are distinguished, including the arrangements of oxygen atoms and the dipole orientation distribution. In region II, ice formation does not occur in the system within 5 × 200 ns simulations. The IWs show a disorder structure, preventing the ice formation process on substrate. The interfacial water molecular orientation distribution and two-dimensional free energy landscape reveals that the electric field can alter the dipole orientation of the interfacial water and lead a free energy barrier, making the ice formation process harder. Our result demonstrates the external electric field can regulate the behavior of IWs, and further affect the ice formation process. The external electric field act as a crystallization switch of ice formation on substrate, shedding light into the studies on the control of ice crystallization.

Numerical Study of Free-Surface Electro-Hydrodynamic Wave Turbulence

Direct numerical simulation of threedimensional chaotic motion of a dielectric liquid with a free surface under the action of external horizontal electric field is carried out. The numerical model takes into account the effects of surface tension, viscosity, and external isotropic random forcing acting at large scales. A transition from dispersive capillary wave turbulence to quasi-isotropic nondispersive EHD surface turbulence with increase of the external electric field strength is numerically observed for the first time. At the regime of developed EHD wave turbulence, the total electrical energy is found to be much greater than the energy of capillary waves, i.e., electrohydrodynamic effects play a dominant role. At the same time, anisotropic effects are detected that lead to the generation of capillary wave packets traveling perpendicular to the external field direction. Despite the revealed anisotropy, the calculated spectrum of EHD wave turbulence is in very good agreement with the analytical spectrum obtained on the basis of dimensional analysis of weak turbulence spectra.

Effects of Field Strength and Silver Nanowire Size on Plasmon-Enhanced N2 Dissociation.

Dissociation of the nitrogen molecule via plasmon-enhanced catalysis using noble metal nanoparticles has been investigated both experimentally and computationally in recent years. However, the mechanism of plasmon-enhanced nitrogen dissociation is still not very clear. In this work, we apply theoretical approaches to examine the dissociation of a nitrogen molecule on atomically thin Agn nanowires (n = 6, 8, 10, 12) and a Ag19+ nanorod. Ehrenfest dynamics provides information about the motion of nuclei during the dynamics process and real-time TDDFT calculations show the electronic transitions and population of electrons over the first 10 s of fs time scale. The activation and dissociation of nitrogen are typically enhanced when the electric field strength increases. However, the enhancement is not always monotonic with field strength. As the length of the Ag wire increases, nitrogen is typically easier to dissociate and thus requires lower field strengths, even though the plasmon frequency is lower. The Ag19+ nanorod leads to faster dissociation of N2 than the atomically thin nanowires. Overall, our detailed study yields insights into the mechanisms involved in plasmon-enhanced N2 dissociation, as well as provides information about factors that can be used to improve adsorbate activation.

Effects of electric field on the filtration characteristics of solid particles in oil

The presence of solid particles in oil can easily lead to surface failure of machine components. In order to reduce the harmful effects of solid particles, it is necessary to remove solid particles from oil. The electrostatic method is an efficient method for removal of solid particles under an applied electric field. However, the filtration mechanism for solid particles in mixed oil–solid systems using electrostatic methods has not been fully investigated. In view of this, an oil–solid separation method based on electric field enhancement is proposed. For this method, a numerical model of oil–solid separation under different electric field strengths is established by coupling the electric and flow field governing equation, the particle-wall collision equation, and the discrete phase tracking equation. Solved by finite element method, the influence of electric field on particle motion and filtration performance of the system is studied. The results indicated that in the mixed oil–solid system, the filtration efficiency is significantly increased by more than 32.97% when an electric field is used. When E > 1 kV/mm, the flow rate of particles into and out of the filter increased with increasing electric field intensity, the deposition became more dispersed, the highest deposition concentration was 3.69 times that without an electric field, and the filtration efficiency decreases but does not exceed 10% as the flow rate increases. When the particle size is greater than 30 µm, the filtration efficiency increases by at least 14.71% for every 1 kV/mm increase in electric field strength, up to a maximum of 97.65%.

Influence of the Electric Field on the Properties of Hydrogenated Graphene

Graphene is currently considered as one of the most promising materials for the creation of new semiconductor devices for various frequency ranges . The influence of an external electric field on the properties of the band diagram of the graphene material , which is a modification of graphene using hydrogen atoms , was studied by simulating from the first principles ( ab initio method ). It was found that an external electric field applied to the graphene structure leads to a substantial change in its band diagrams , which is associated with a change in their type . At small values of external electric field strength , approximately up to 0.3 a.u . (1 a.u . ≈ 51.4 1010 V/m), we observe graphane zone diagrams with straight minimal gap for Г valley between conduction and valence zones . With further increase in external electric field strength the zone diagrams show indirect minimal gap . With even higher values of external electric field strength , which exceed 0.8 a.u ., graphane band diagrams take on a form peculiar to metallic structures . These dependences and the resulting graphene parameters could be the basis for new heterostructure devices containing layers of graphene and other semiconductor materials .

Effects of rod radius and voltage on streamer discharge in a short air gap

Streamer discharge is the inaugural stage of gas discharge, and the average electron energy directly determines the electron collision reaction rate, which is a key parameter for studying streamer discharge. Therefore, taking into account the average electron energy, this work establishes a fluid chemical reaction model to simulate and study the course of evolution of a streamer discharge in a 5 mm rod–plate gap, considering 12 particles and 27 chemical reactions. It introduces the electron energy drift diffusion equation into the control equation, and analyzes the temporal and spatial changes of average electron energy, electric field intensity and electron density with change in rod radius and voltage. The effects of voltage and rod radius on the course of streamer discharge can be reflected more comprehensively by combining the average electron energies. Three different values of 0.3 mm, 0.4 mm and 0.5 mm are set for the rod radius, and three different values of 5 kV, 6 kV and 7 kV are set for the voltage. The influence of an excitation reaction on the streamer discharge is studied. The findings indicate that, as voltage raises, the streamer head’s electron density, electric field and average electron energy all rise, and the streamer develops more quickly. When the rod radius increases, the electron density, electric field and average electron energy of the streamer head all decrease, and the streamer’s evolution slows down. When an excitation reaction is added to the model, the average electron energy, the magnitude of the electric field and the density of electrons decrease, and the evolution of the streamer slows down. An increase in average electron energy will lead to an increase in electric field strength and electron density, and the development of the streamer will be faster.

Investigation on the photocatalytic property of direct Z-type van der Waals g-C3N4/AlN heterojunction and its mechanism

Using hybrid density functional method, the electronic, interfacial and optical characters of the g-C3N4/AlN heterojunction as well as the effect of electric field and biaxial strain on its photocatalytic performance were systematically studied. The g-C3N4/AlN is a direct band gap semiconductor (2.71 eV) with stagger band alignment structure and exhibits direct Z-scheme photocatalytic reaction mechanism. Under the external electric field and biaxial strain, the staggered band feature of the heterostructure is retained and its VBM potential and CBM potential still have strong oxidation and reduction capabilities, which can meet the redox potential conditions of photocatalytic water-splitting. Meanwhile, the band gap gradually decreases with the increase of electric field strength ranged from −0.5 V/Å to 0.5 V/Å and 1% compressible strain tunes the heterostructure from direct band gap to indirect band gap. Our work provides a theoretical basis for the design of g-C3N4-based heterojunctions with high photocatalytic performance.

Effects of GaN cap layer thickness on photoexcited carrier density in green luminescent InGaN multiple quantum wells

The effects of GaN cap layers on the optical properties of green luminescent InGaN-based multiple quantum wells were studied by photoluminescence (PL) spectroscopy. The PL peak energy under the selective excitation of the InGaN well layers was lower than that under the band-to-band excitation of the GaN barrier layers. The difference in the PL peak energies between the selective and band-to-band excitations decreased as the cap layer thickness increased, indicating an increase in the nonradiative recombination of photogenerated carriers in the barrier layers. Moreover, the internal quantum efficiency under selective excitation decreased as the cap layer thickness increased because of the increase in the internal electric field strength.

Effect of electric and magnetic field on thermal property of two dimensional harmonic oscillator

The energy spectrum of a 2D quantum harmonic oscillator confined by a hard wall circular cavity of size r0 in the presence of static electric and the magnetic field is computed numerically using the Bessel function basis set and the linear variational process. The effect of the size of the circular cavity, magnetic field, and electric field strength is studied on the energy levels, the radial transition matrix elements, and the thermal properties of the system like specific heat, Helmholtz free energy, and entropy using canonical partition function. Blueshift is observed for an increase in magnetic and electric field strength. The harmonic oscillator problem is critical for understanding any natural system that undergoes deformation and performs simple harmonic motion.

TDDFT calculations of the PETN's ultraviolet absorption spectrum under the electric field loading.

The UV(ultraviolet) absorption spectrum of PETN under different electric field loading directions(X, Y, and Z) with the value of strength range from 0.001 a.u. to 0.006 a.u. was calculated with the TDDFT(Time-dependent density functional) in this work. With the increase of electric field strength, the absorbance of PETN in the ultraviolet band decreases. To explain the action mechanism of the electric field on PETN UV(ultraviolet) absorption spectrum, we analyzed and counted the contribution rate, oscillator strength, and vertical excitation energy of the main excitation process whose contribution rate to the UV absorption spectrum is greater than 10%. The contribution of PETN to the UV spectrum in all directions without an electric field was also listed to investigate the anisotropy of PETN in the excitation process under an electric field. The hole-electron analysis showed that the electric field will enhance the charge transfer characteristics in the excitation process of PETN. To investigate the anisotropy of the response under different electric field application directions, the contribution of the UV absorption spectrum in different directions was studied. Optimization and TDDFT calculation were performed at the level of M06-2X/def2-TZVP and PBE0/def2-TZVP respectively, with Gaussian09 program. The hole-electron analysis and UV absorption spectrum plotting were performed with Multiwfn3.8.

Heat transfer and electro-osmotic analysis on peristaltic pumping of a fractional second-grade fluid through a cylindrical tube

Most of the earlier studies intended on the peristaltic pumping of non-Newtonian fluids via channels/tubes to better know the flow activities of flowing systems. The extant effort is modeled to examine the peristaltic motion of the viscoelastic fluid through a cylindrical tube to characterize the rheological features of blood in the vascular system by incorporating the electro-osmotic phenomenon. Caputo’s definition provides analytical solutions to the dilemma. To evaluate the potential function, the Debye–Huckel linearization approximation is utilized. The long-wavelength [Formula: see text] and low Reynolds number approximations [Formula: see text] are used to simplify the simultaneous equations. The effects of physical constraints depicting the flow phenomena are obtained and conferred via graphs. The impact of several regulatory elements is deliberated and exposed in a succession of figures. The significant outcome of the result is that the pressure gradient is consistently enhanced as the external electric field strength increases. It is also observed that the growing applied electric field strength can control the negative value of the pressure gradient. This work is relevant to the electrophoresis in hematology, electrohydrodynamic therapy, and biometric electro-osmotic pumps. The present results provide a significant baseline for experiment analyses and more general models of microvascular blood flow.

Atomization and combustion characteristics of a biodiesel–ethanol fuel droplet in a uniform DC electric field

Electric field has the potential to influence the combustion characteristics of hydrocarbon fuel. In this paper, the atomization and combustion characteristics of the droplets of biodiesel and biodiesel–ethanol blend in a uniform direct-current electric field were investigated using photography. It was revealed that a certain electric field strength could induce droplet deformations and cone jets. For the droplet blended with 10 vol. % ethanol, the sizes of the secondary droplets from bubble breakups decreased with the increase in electric field strength, possibly due to the Coulomb repulsion in the ligament. The high breakup intensity of the droplet blended with 30 vol. % and 50 vol. % ethanol covered up the effect of electric field on the sizes of secondary droplets from bubble breakups. During the entire range of electric field strength, cone jets generated smaller secondary droplets in comparison with bubble breakups. Moreover, the electric field distorted the flame morphology, especially the flame width increased at the electric field strength of 50 kV/m. The maximum droplet temperature decreased with the electric field strength, in addition to the biodiesel droplet. Overall, the electric field ameliorates fuel droplets' atomization and combustion characteristics.

Electrophoretic coalescence behavior of oil droplets in oil-in-water emulsions containing SDS under DC electric field: A molecular dynamics study

The presence of oil droplets in oil-in-water (O/W) emulsions seriously affects the efficiency of wastewater purification, and the appropriate addition of surfactants can effectively improve the demulsification process. In this paper, the electrophoretic coalescence behavior of oil droplets containing anionic surfactant sodium dodecyl sulfate (SDS) under a direct current (DC) electric field was studied based on molecular dynamics (MD) simulations, and four typical stages of oil droplet migration coalescence were defined. The weak interactions between SDS and water and between SDS and n-hexane are mainly van der Waals interactions, while a small number of hydrogen bonds are formed between SDS and water and between water molecules internally. With the increase of electric field strength (E), the deformation of oil droplets after aggregation increases, and the contact angle with the electrode plate becomes smaller. The interfacial tension between oil and water decreases and then increases with increasing surfactant concentration, reaching a minimum value of 32.52 mN/m when the number of SDS molecules (n) around each oil droplet is 55. When E = 1.2 V/nm and n = 55, the coalescence time of oil droplets reaches the minimum value of 2.425 ns. The migration rate of oil droplet far from the anode is greater than that of oil droplet near the anode, which is due to the larger combined forces on the former. The results reveal the microscopic mechanism of oil droplet migration and coalescence under the coupling effect of DC electric field and anionic surfactant, which could provide theoretical guidance for the improvement of oily wastewater purification process.

Mechanism study of the conductivity characteristics of cellulose electrical insulation influenced by moisture

Cellulose insulating paper is widely used in the power industry for its good electrical insulating properties. Moisture sharply increases its conductivity, which directly leads to the weakening of insulation performance and greatly increases the risk of subsequent electric field distortion and insulation breakdown. This paper focuses on the microscopic mechanism of moisture changing the characteristics of charge transport in cellulose insulation and attempts to reveal the related conductivity mechanism. To achieve this purpose, microscopic and macroscopic perspectives are integrated and several simulation and experimental methods are utilized comprehensively. The molecular dynamics simulation results showed that most water molecules in damped cellulose were individually and uniformly adsorbed on the hydroxyl groups by hydrogen bond, and the quantum chemistry computation results showed that the lowest unoccupied molecular orbital more appeared on the water molecule and the corresponding density of state increased. Then, experimentally, it was confirmed that the trap energy level decreased by the thermally stimulated current method. On this basis, the promotion effect of moisture on charge transport is predicted and verified by polarization and depolarization current methods. As the moisture content increased, more charge carriers escaped from the trap by hopping and participated in long-range continuous charge motion. Therefore, after dampness, the current of cellulose insulating paper increased exponentially with the increase in electric field strength, which was consistent with the hopping conductivity mechanism.