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Nowadays, electric fields above the ground are measured mainly by so‐called ‘field mill type’ sensor systems. However, their measurements are limited to vertical field component only due to its technical constraint. Out of necessity of measurements of electric field components in arbitrary directions in any spaces, a linear dipole type DC electric field sensor system, which can be immersed within a fully uniform electric field, was developed. However, it had been remained unknown whether its sensor output is parameter‐dependent or not, and unknown whether it can provide reliable intensity value of measured electric fields or not. In order to clarify these points, test observations of natural electric fields have been conducted by means of plural sensor systems having different values of parameter. Obtained electric field intensity derived from the observed data has shown a parameter‐dependence despite that it should be constant for any parameter values. After a detailed analysis of the effect of the parameter along the equivalent electric circuit of the sensor system, a field‐calibrating formula, which can make the sensor system to be parameter‐independent, has been found. Finally, the linear dipole type DC electric field sensor system for obtaining reliable electric field intensities has been established. © 2024 The Author(s). IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Electrical stimulation has recently received attention as noninvasive treatment in skin wound healing with its outstanding biological property for clinical setting. However, the complexity of equipment for applying appropriate electrical stimulation remains an ongoing challenge. Here, we proposed a strategy for skin scar inhibition by providing electrical stimulation via a multilayer stacked electret (MS‐electret), which can generate direct current (DC) electric field (EF) without any power supply equipment. In addition, the MS‐electret can easily control the intensity of EFs by simply stacking electret layers and maintain stable EF with the surface potential of 3400 V over 5 days owing to the injected charges on the electret surface. We confirmed inhibition of type 1 collagen and α‐SMA expression of human dermal fibroblasts (hDFs) by 90% and 44% in vitro, indicating that the transition of hDFs to myofibroblasts was restricted by applying stable electrical stimulation. We further revealed a 20% significant decrease in the ratio of myofibroblasts caused by the MS‐electret in vivo. These findings present that the MS‐electret is an outstanding candidate for effective skin scar inhibition with a battery‐free, physiological electrical microenvironment, and noninvasive treatment that allows it to prevent external infection. [ABSTRACT FROM AUTHOR]

Abstract Electrical stimulation has recently received attention as noninvasive treatment in skin wound healing with its outstanding biological property for clinical setting. However, the complexity of equipment for applying appropriate electrical stimulation remains an ongoing challenge. Here, we proposed a strategy for skin scar inhibition by providing electrical stimulation via a multilayer stacked electret (MS‐electret), which can generate direct current (DC) electric field (EF) without any power supply equipment. In addition, the MS‐electret can easily control the intensity of EFs by simply stacking electret layers and maintain stable EF with the surface potential of 3400 V over 5 days owing to the injected charges on the electret surface. We confirmed inhibition of type 1 collagen and α‐SMA expression of human dermal fibroblasts (hDFs) by 90% and 44% in vitro, indicating that the transition of hDFs to myofibroblasts was restricted by applying stable electrical stimulation. We further revealed a 20% significant decrease in the ratio of myofibroblasts caused by the MS‐electret in vivo. These findings present that the MS‐electret is an outstanding candidate for effective skin scar inhibition with a battery‐free, physiological electrical microenvironment, and noninvasive treatment that allows it to prevent external infection.

Copyright of Journal of East China University of Science & Technology is the property of Journal of East China University of Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, a new method for study of the process of domain orientations and space charge relaxation in ferroelectrics using the surface acoustic waves (SAW) has been developed. The results of an experimental study of the dc electric field influence on the parameters of SAW propagation in piezoceramics with different ferroelectric "hardness" are presented. [ABSTRACT FROM AUTHOR]

To address the problem of poor development due to difficult water injection in tight oil, the application of DC electric field is proposed to enhance the recovery of tight oil. Taking the tight sandstone core of the Upper Trias- sic Yanchang Formation in the Ordos Basin as the research object, the DC electric field displacement effect and the mechanism of action were investigated through DC electric field constant velocity displacement experiments, wetting angle measurements and XRD test experiments. The study shows that the DC electric field enhanced recovery rate of tight oil is positively correlated with the electric field intensity; the development effect when the DC electric field is applied at the beginning of water flooding is better than that when the DC electric field is applied after the end of water flooding, both of which can increase the average recovery rate through water flooding by 29. 06 and 14. 68 percentage points respectively at 10 V; the recovery rate is accelerated after the DC electric field is applied; the DC electric field can not only reduce the flow resistance through electroosmotic flow to decrease the difficulty of water injection, but also enhance the hydrophilicity of the rock through electrochemical reaction to improve the oil displacement efficiency. The study provides a new idea for the efficient development of tight oil. [ABSTRACT FROM AUTHOR]

The effects of applying external electric fields on the coefficient of friction of a selected elastomer during mechanical interaction with steel and copper surface oil (counter samples) immersed in a pin-on-disc setup were studied and investigated. The synthetic base oils used were PAG 68 and PAO 6. The elastomer selected for the study is commonly used in the manufacture of rotary lip seals. During the investigations, the viscosity of the oils tested was also experimentally determined in the temperature range of between 286 K and 393 K. It was found that the external electric field had a significant effect on the friction coefficient, depending on the type of base oil, the angular velocity of the load force, and the counterpart. It was observed that for both oils tested, the coefficient of friction values decreased by about 30% when an external DC electric field was applied. In addition, a simple numerical model of the friction interface was proposed and studied. The experimental results were complemented by molecular simulations to determine the interaction between the lubricant molecule and the metal surface. Furthermore, molecular models of the metal surface and lubricant molecules were simulated using ReaxFF and COMPASS force fields to determine adsorption energies. [ABSTRACT FROM AUTHOR]

The charge accumulation phenomenon at the gas–solid interface under the co-action of DC electric field and temperature gradient is of great significance, but its long-time evolution characteristics are still unclear. In this work, the accumulation and dissipation characteristics of the surface charge on the epoxy-SF6 interface within 216 h were obtained, indicating that, (a) the normal surface electric field is increased by the temperature gradient along the gas–solid interface, which results in a prominent increase in the surface charge density; (b) there are different evolution processes of surface charge in high and low temperature regions under the co-action of DC-temperature gradient, and the increase of the charge trap density caused by the degradation of solid material is considered to be an important reason for the charge evolution; (c) the total charge dissipation ratio within 600 s decreases with the increase of charging time in DC electric field, and the surface charge dissipates mainly to the gas side of the interface; (d) the large amount of charge accumulated at the interface distorts the surface electric field at the triple junction points. The total electric field strength at the low-temperature tri-junction point increases by 35.5%, while the direction of the tangential field at the high-temperature tri-junction point reverses during the long-time co-action of the DC-temperature gradient. The results of this work may be helpful to understand the long-time charge evolution characteristics of the gas–solid interface under the DC-temperature gradient and to reveal the failure mechanism of the gas–solid interface. [ABSTRACT FROM AUTHOR]

Effect of DC electric field on lean premixed biogas turbulent flame structure at low and medium turbulence intensity was studied experimentally using OH-PLIF. OH signal distribution, turbulent burning velocity and flame structure geometric parameters were derived. Results show that downward electric field could broaden the downstream burned gas and push the flame tip down. The flame base is closer to the burner rim in downward electric field for the modification of thermal diffusion and flow modification caused by ionic wind. The effect on flame tip height reduction is more obvious for biogas flame with a higher CO2 ratio. According to the flame structure analysis, the turbulent burning velocity of biogas is increased slightly due to the modification of flow field by ionic wind generated by downward electric field, and the increment decreases with the increase of turbulence intensity. In addition, there's a decrease in mean flame surface density and an increase in centerline flame brush thickness. The flame surface curvature PDF distribution is nearly not affected by the application of DC electric field. For turbulent flames, the effect of electric field is non-uniform and inconstant, which induces extra flow perturbation. This perturbation is different from turbulence, and the combined effects lead to the variation of flame structure. [ABSTRACT FROM AUTHOR]

The effects of applying external electric fields on the coefficient of friction of a selected elastomer during mechanical interaction with steel and copper surface oil (counter samples) immersed in a pin-on-disc setup were studied and investigated. The synthetic base oils used were PAG 68 and PAO 6. The elastomer selected for the study is commonly used in the manufacture of rotary lip seals. During the investigations, the viscosity of the oils tested was also experimentally determined in the temperature range of between 286 K and 393 K. It was found that the external electric field had a significant effect on the friction coefficient, depending on the type of base oil, the angular velocity of the load force, and the counterpart. It was observed that for both oils tested, the coefficient of friction values decreased by about 30% when an external DC electric field was applied. In addition, a simple numerical model of the friction interface was proposed and studied. The experimental results were complemented by molecular simulations to determine the interaction between the lubricant molecule and the metal surface. Furthermore, molecular models of the metal surface and lubricant molecules were simulated using ReaxFF and COMPASS force fields to determine adsorption energies.

Geothermal energy, recognized for its clean and vast developmental potential, finds untapped promise in many oil fields developed through water injection. However, challenges such as the high costs associated with drilling and development, the expansion of water-clay expansion, and low rock permeability have constrained the broader exploitation of geothermal resources. Here, to address these challenges and harness low-permeability geothermal energy from abandoned wells, this work introduces a novel approach: DC-assisted circulation water injection technology. This study employs the Green function, Newman product, and boundary element methods to develop semi-analytical and numerical models, incorporating a DC electric field to simulate the optimization effect of this field on heat extraction. This work evaluates and optimize the lifetime and economic effects of abandoned wells using the Non Sorting Genetic Algorithm II. Results show that the semi-analytical model monitors the reservoir temperature parameter to optimize the timing for circulation water injection. Additionally, our numerical model demonstrates that, over a span of 5000 days, a network of wells could generate a revenue of $9.158 million. In summary, DC-assisted abandoned wells to develop geothermal reservoirs is not only feasible but also enhances reservoir permeability and porosity through an electrical conductivity effect, significantly improving heat energy recovery. [Display omitted] [ABSTRACT FROM AUTHOR]

• The electric field significantly affects the flames and atomization characteristics. • The extinction time of Fe-diesel droplets increased in the positive electric field. • The soot oxidation increased with the negative electric field. • The electric field effect caused a decreasing trend in the ignition delay of diesel droplets, while the addition of Fe particles caused an increasing trend. • The highest maximum flame temperature was measured at the negative electric field. The application of electrical techniques such as electric field, polarization, and ionization in the field of combustion makes many positive developments possible. The electric field effect offers significant advantages in controlling flame stability and reducing soot formation during the combustion of fuels. Also, the conditioning effect can improve particle oxidation during combustion for hydrocarbon fuels containing metal particle inclusions with high calorific value. This study focuses on investigating the combustion and atomization behavior of Fe additive diesel fuel droplets at electric field strengths of E = 5 V/m, E = 6.7 V/m, and E = 10 V/m and in positive (↑) and negative (↓) electric field directions. The experiments were carried out by igniting a fuel droplet suspended on a ceramic wire with an arc at the center of the electric field between two conductive plates in a combustion chamber with optical apertures. The combustion processes were recorded with an optical system consisting of a high-speed camera and a thermal camera. Combustion and atomization behavior were characterized by sequential flame and droplet atomization images, respectively. The droplet shape change and flame behavior results were comparatively evaluated according to the d2-law. Ignition delay and extinction times were determined by processing threshold technique and maximum flame temperatures were determined by processing thermal camera images. The results showed that increasing the electric field intensity in the negative electric field direction resulted in improved soot oxidation, and Fe particles burnt efficiently. Ignition delay times showed a decreasing trend with an electric field effect and an increasing trend with the addition of Fe particles. The highest maximum flame temperature and lowest extinction time were recorded as 785 K and ∼ 578.34 ms for Diesel/Fe/100(↓) fuel droplet, respectively and Fe particles did not exhibit microexplosion phenomena at E = 10 V/m. In this study, it has been shown that an effective oxidation can be achieved for Fe particles by increasing the mobility of ionized species in the flame zone under the effect of electric field and a homogeneous thermal field can be created in the flame zone even in fuels with particle addition at increasing electric field intensities. [ABSTRACT FROM AUTHOR]

The effects of different electrode on Solanum nigrum L. seed germination were determined. The result showed that germination percentage (GP) of seeds in treatment T2 (titanium electrode) was 26.6% higher than in control (CK, without electric field). High potassium and calcium concentrations were beneficial for seed enzymatic activity in treatment T2, which could partly explain the increase in GP. Cd accumulation (μg/pot) in S. nigrum treated with any electric field was significantly higher (p <0.05) than in CK without electric field. Specifically, Cd accumulation under the treatment T3 (stainless steel electrode) was the highest both in roots and shoots; this accumulation in shoots and roots were 74.7 % and 67.4 % higher for stainless steel than in CK. This increase must have been associated with a higher Cd concentration in plants and did not exert a significant effect on the biomass. In particular, Cd concentrations in roots and shoots under stainless steel treatment were both significantly higher than in CK (p <0.05), which had to be related to the higher available Cd concentration in the soil in the middle region. Furthermore, it could be attributed to altered soil pH and other soil properties. Moreover, none of the biomasses were significantly affected (p <0.05) by different electrode materials compared to CK. [Display omitted] [ABSTRACT FROM AUTHOR]

DC electric field intensified oil and gas production technology is widely used in oil and gas field in China. Aiming at the characteristics of the coal reservoir medium under the electric field, we have the self-made adsorption and desorption experimental system of coal and rock samples under the high-strength electricity. Using the anthracite coal from Jiulishan mine and Zhaogu No.2 mine to carry out gas adsorption and desorption experiments with real-time on-line electricity. And we carried out the nuclear magnetic resonance (NMR) experiment and mercury intrusion experiment of coal samples. Our experiments show that: (i) the high-strength direct current alone to intensify the adsorption process, we found that have a characteristic field strength, which is beneficial to the adsorption of gas by the coal sample. The adsorption capacity and the field strength have a parabolic relationship, and the maximum value under characteristic field strength; The high-strength direct current is applied in the whole process of adsorption and desorption, we found that the desorption volume and desorption rate were obviously enhanced; The high-strength direct current alone to intensify desorption process, the experiment phenomenon is same as the former, but the enhancing result is weaker than the whole process with the electric field; In the experiment of direct current intensifying, the gas absorption volume, desorption volume and desorption rate are the largest at 60 kV/m that we were preliminarily determined to be the advantage field intensity of coal sample; Under this field intensity, the Gibbs free energy reaches the maximum, increased by 23.5% and 3.01%, respectively, the P2 peak area of T2 spectrum increases nearly 9 times, and the peak shifts to the right. At the same time, the proportion of the specific surface area of the micropores in the mercury injection experiment decreased, and the proportion of the pore volume increased. These together indicated that the advantageous field strength has the effect of increasing pores and cracks in the strengthening effect of the coal sample. And it is reflected in the macroscopically to promote adsorption and promoting desorption. In this paper, we explain the relationship among direct current electric field, gas adsorption and desorption from the experimental point of view. The experimental results provide a new perspective for the design of the internal surface of the coal body through a direct current electric field and it can make the internal surface of coal rock has the characteristics of efficient gas extraction. [ABSTRACT FROM AUTHOR]

In this study, the electrical potential distributions on aluminum bipolar electrodes (BPEs) subjected to bipolar anodization in a direct current (DC) electric field were investigated. Aluminum sheets were used as BPEs, suspended in an electrolyte solution, and positioned either vertically or horizontally at the center of a cell. The results of reflective interference measurements, depth-profiling analysis, and re-anodization clearly revealed that the thicknesses of the porous alumina films and barrier layers near the aluminum substrates can be taken to represent the potential distributions on the horizontally located BPEs; the thickest anodic alumina was formed at the edge of the anodic pole of the BPE, and its thickness continuously decreased in the direction of the cathodic pole. Furthermore, the area of the anodic reaction was much larger than expected, accounting for 90% of the BPE.

The anisotropy of the conductivity and the shape of the I–V characteristics for a two-dimensional quantum superlattice with the nonharmonic electron dispersion law are investigated for different directions of the current and field applied to the structure relative to the superlattice axes. The anisotropy of the characteristics and the conditions for the occurrence of multivalue I–V characteristics in different current flow modes are discussed. It is shown that the deviation of the electron dispersion law in a two-dimensional quantum superlattice from the harmonic one in a strong dc electric field noticeably affects the shape of the I–V characteristic of a two-dimensional quantum superlattice. Several current peaks in a strong field are caused by both mixing of the current lines for directions orthogonal to the applied field and electron transport over Stark-ladder levels formed in different miniband valleys. [ABSTRACT FROM AUTHOR]

The abnormal temperature rise of glass fibre reinforced polymer (GRP) composite in the composite insulator, which has been reported as the early stage of decay-like fractures, has gained significant attention from both industrial and academic sectors. In this study, GRP rod samples, obtained from composite insulators were subjected to hygrothermal ageing and were tested under the conditions according to IEC 62217. The leakage current, partial discharge and temperature rise of the samples were measured. All three parameters tended to increase with the ageing time under AC and DC electric fields. The power contribution supplied by partial discharge could be ignored. Simulation results proved that the temperature rise was mainly caused by the volume current. Under the DC electric field, the conductive current was the heating source, whereas under the AC electric field, the heating power was supplied by both conductive current and the polarisation loss. The content of absorbed moisture in the GRP rod sample showed a linear relationship with the temperature rise. The moisture absorption property can be used as an index to evaluate the ageing state of GRP rod in the composite insulator. [ABSTRACT FROM AUTHOR]

Measurement of electric fields is crucial for the evaluation of the electromagnetic environment in electric power transmission system. Due to limited transmission corridor resources, the hybrid transmission lines including high‐voltage alternating current and high‐voltage direct current (HVAC/HVDC) are more common nowadays. However, commonly used field‐mill direct current electric field sensors (DC EFSs) can only be used beneath HVDC lines and the emergence of alternating current (AC) electric fields has adversely affected measurement results recorded by DC EFS. In this work, a DC EFS was designed that is capable of measuring ground‐level DC electric fields generated by overhead HVAC/HVDC transmission lines in a hybrid corridor. A field‐mill structure was used to modulate the DC and AC hybrid electric field and then a narrow band‐pass filter was used to realise suppression of the AC electric field signal. Subsequently, the phase‐sensitive detection method was used to realise amplitude demodulation and phase discrimination of the DC electric field. Sensor prototypes based on the foregoing method were experimentally tested in the China national high‐voltage base. These DC EFSs could be mass‐produced conveniently from current field‐mill for hybrid corridors application. [ABSTRACT FROM AUTHOR]

We present a biocompatible contactless gel actuator based on poly(methacrylic acid) with magnesium counterions (MgPMA) that, being placed in sodium chloride solution, is able to generate a high value of active mechanical force in a DC electric field. Force generation of the gel goes simultaneously with its swelling due to the osmotic pressure provided by the ionic exchange in the MgPMA polyelectrolyte matrix induced by the electric current. An increase in the charge density of the polymeric network enhances the mechanical stiffness of the gel, which provides negative feedback to force generation. The extent of such influence depends on the networking density of the gel matrix. As a result, soft MgPMA gels with low networking density show higher level of force generation than dense gels with high networking density. It is shown that cylindrical gel samples of ca 8 mm in length and ca 11 mm in diameter immersed in NaCl solution some distance apart from platinum electrodes are able to exert a force of up to 0.4 N in a DC electric field for a constant length of sample with a rate of ca 1.0 mN per second on average. [ABSTRACT FROM AUTHOR]

In this study, the impact of DC electric and magnetic fields on the output power, open-circuit voltage, and photocurrent density of a silicon photovoltaic (PV) cell/module is assessed. In this regard, the influence of DC electric and magnetic fields is first evaluated in theory by formulating and discussing related basis and concepts. Then, experimental measurements and data obtained from two different sets of experiments are given that verify theoretical results. In theory and practice, it is shown that depending on the direction of a DC electric field applied to a silicon PV cell/module, it causes an increase or reduction in the output power and open-circuit voltage of the PV cell/module. In detail, when the DC electric field points in the direction of the junction electric field of the PV cell(s), the output power and open-circuit voltage of the silicon PV cell/module increase, otherwise the output power and open-circuit voltage decrease. Regarding the magnetic field, it is proved that depending on the direction of a DC magnetic field applied to a silicon PV cell/module, different effects are observed. In detail, when the DC magnetic field points along the junction electric field of the PV cell(s), it has no effect on the output power and open-circuit voltage of the silicon PV cell/module. But, the output power and open-circuit voltage of the silicon PV cell/module decrease when the DC magnetic field points in the other directions. Moreover, the reduction in the output power and open-circuit voltage reaches its peak when the DC magnetic field is applied in the direction perpendicular to the junction electric field. [ABSTRACT FROM AUTHOR]

Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A polypropylene (PP) film is usually used as a dielectric material in capacitors as well as cables. However, PP films may degrade because of the combined effect of temperature and electric field. In an earlier study, plain PP films and PP films loaded with nano-metric natural clay were studied under sinusoidal (AC) electric fields at power frequency and temperatures above the ambient. To better understand the electrical characteristics of PP film under various conditions, the objective of this study is to determine the time-to-breakdown of the plain PP and PP filled with 2% (wt) natural nano-clay when subjected to time-invariant (DC) electric fields at elevated temperatures. In order to achieve this objective, the effects of uniform as well as non-uniform electric fields were compared at the same temperature for the PP film. In this study, experimental results indicated that the time-to-breakdown of all PP films, plain or filled with nano-clay, decreases with the increase in electric field intensity, non-uniformity of the electric field, and temperature. It was also found that the time-to-breakdown of PP film filled with 2% (wt) natural nano-clay under DC electric field is longer and less sensitive to temperature. Furthermore, when compared with the results under the uniform electric field, PP film filled with 2% (wt) nano-metric natural clay indicates shorter time-to-failure under non-uniform DC electric fields. Finally, the morphology of the samples was observed by digital camera, optical micrography, and SEM, to better understand the mechanism of the breakdown.

In order to study the influence mechanism of dielectrically coated electrode in SF(6) gas under DC electric field on metal particle lift-off, experimental platform is setup and motion trajectory is recorded by high-speed camera. The experiment shows that with the increasing of SF(6) gas pressures, the lift-off field of metal particle is increased and the time to reach the high-voltage electrode shortened. Instantaneous displacement of metal particle is gained by image processing and computational method of charge quantity is raised, analysing of charge quantity shows that the metal particle's charge quantity decreases. Meanwhile, theoretical analysis model of field distribution around metal particle is established, result indicates that there is an enhance of electric field between coating and metal particle and a transform of charge density distribution, which leads to a downward polarisation force for metal particle. The decreasing of the electric charge quantity and the downward polarisation force results in the increasing of the lift-off field. This article maintains that partial discharge is the charging mechanism of metal particle; the enlargement of SF(6) gas pressure brings about the raise of initial electric field of partial discharge, causing the increase of downward polarisation force with higher electric field to lift-off.

With the development of high-voltage direct-current (HVDC) transmission projects, the issue of electromagnetic compatibility has become more and more severe, especially the synthetic ion flow electric field. The DC electric field is inseparable from the equipment insulation, the safety of the system operation, and effects on organisms nearby. The measurement of the synthetic electric field of ion flow has been a major difficulty due to the influence of ion currents and distorted field. A differential electric field sensor for measuring the synthetic electric field is proposed. The calibration method and the experimental device for the measurement of the air synthetic electric field of ion flow are presented. Calibration experiments show that the calibration method is practical and effective, and the test result from the sensor is in good agreement with the theoretical value. The experiments in the library show the validity of the calibration method and the excellent performance of the sensor.

Highlights • The interactions between an oil droplet and a horizontal solid surface was analyzed. • There is a separation distance between an oil droplet and a solid surface. • The droplet and solid surface zeta potentials affect the droplet moving direction. • The droplet moving velocity increases with the decrease of the separation distance. Abstract This work numerically investigated the translational velocity of a negatively charged oil droplet in the water near a negatively charged solid surface under a DC electric field. The equilibrium separation distance between the charged oil droplet and the charged solid surface is calculated under different parameters and the translational motion of the droplet near the solid surface is simulated via a three-dimensional mathematical model. The results indicate that the velocity of the droplet is higher under a larger zeta potential of the solid surface and a smaller zeta potential of the droplet. When the absolute value of the negative zeta potential of the droplet is larger than that of the solid surface, the droplet will move in opposite direction of the electric field. It is also found that the droplet translational velocity increases with the decrease of the separation distance between the oil droplet and the solid surface. [ABSTRACT FROM AUTHOR]

Satellite‐based direct electric field measurements deliver crucial information for space science studies. Yet they require meticulous design and calibration. In‐flight calibration of double‐probe instruments is usually presented in the most common case of tenuous plasmas, where the presence of an electrostatic structure surrounding the charged spacecraft alters the geophysical electric field measurements. To account for this effect and the uncertainty in the boom length, the measured electric field is multiplied by a parameter called the shorting factor (sf). In the plasmasphere, the Debye length is very small in comparison with spacecraft dimension, and there is no shorting of the electric field measurements (sf = 1). However, the electric field induced by spacecraft motion greatly exceeds any geophysical electric field of interest in the plasmasphere. Thus, the highest level of accuracy in calibration is required. The objective of this work is to discuss the accuracy of the setting sf = 1 and therefore to examine the accuracy of Van Allen Probes electric field measurements below L = 2. We introduce a method to determine the shorting factor near perigee. It relies on the idea that the value of the geophysical electric field measured in the Earth's rotating frame of reference is independent of whether the spacecraft is approaching perigee or past perigee, that is, it is independent of spacecraft velocity. We obtain that sf = 0.994 ± 0.001. The resulting margins of errors in individual electric drift measurements are of the order of ±0.1% of spacecraft velocity (a few meters per second). Plain Language Summary: Large‐scale electric fields are naturally present in space. They are key to understanding plasma dynamics. Yet they are notoriously difficult to measure directly. In situ electric field measurements are especially challenging very close to Earth, when spacecraft pass through perigee with maximum velocity in a strong magnetic field. The field instruments onboard the Van Allen Probes are the first to be accurate enough to measure the geophysical electric field around magnetic equator, even below 3 Earth radii. In this work, we introduce a method to calibrate the data and to determine the margins of errors for the Van Allen Probes electric drift measurements in the Earth's plasmasphere. The corresponding margins of errors are remarkably small (<10 m/s for each individual electric drift measurement). Therefore, this work further demonstrates the ability of Van Allen Probes instruments to resolve small variations in the geophysical electric drift, even very close to Earth. It is the first time that the calibration of near perigee DC electric field measurements is discussed. Such method could potentially be transposed to other missions and other sets of satellite‐based electric field measurements to further advance our understanding of transport and energization in space plasmas. Key Points: Electric field experiments require calibration of the shorting factor, a parameter that converts measurements into actual electric fieldWe present a method to determine the shorting factors of the Van Allen Probes double‐probe electric field instruments near perigeeUncertainty in individual electric drift measurements due to uncertainty in the value of the shorting factor is smaller than 10 m/s [ABSTRACT FROM AUTHOR]

In order to study the influence mechanism of dielectrically coated electrode in SF6 gas under DC electric field on metal particle lift-off, experimental platform is setup and motion trajectory is recorded by high-speed camera. The experiment shows that with the increasing of SF6 gas pressures, the lift-off field of metal particle is increased and the time to reach the high-voltage electrode shortened. Instantaneous displacement of metal particle is gained by image processing and computational method of charge quantity is raised, analysing of charge quantity shows that the metal particle's charge quantity decreases. Meanwhile, theoretical analysis model of field distribution around metal particle is established, result indicates that there is an enhance of electric field between coating and metal particle and a transform of charge density distribution, which leads to a downward polarisation force for metal particle. The decreasing of the electric charge quantity and the downward polarisation force results in the increasing of the lift-off field. This article maintains that partial discharge is the charging mechanism of metal particle; the enlargement of SF6 gas pressure brings about the raise of initial electric field of partial discharge, causing the increase of downward polarisation force with higher electric field to lift-off. [ABSTRACT FROM AUTHOR]

With the development of high-voltage direct-current (HVDC) transmission projects, the issue of electromagnetic compatibility has become more and more severe, especially the synthetic ion flow electric field. The DC electric field is inseparable from the equipment insulation, the safety of the system operation, and effects on organisms nearby. The measurement of the synthetic electric field of ion flow has been a major difficulty due to the influence of ion currents and distorted field. A differential electric field sensor for measuring the synthetic electric field is proposed. The calibration method and the experimental device for the measurement of the air synthetic electric field of ion flow are presented. Calibration experiments show that the calibration method is practical and effective, and the test result from the sensor is in good agreement with the theoretical value. The experiments in the library show the validity of the calibration method and the excellent performance of the sensor. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Flocculant-free flocculation using DC electric field for material recycling. • Deformation of electric double layer by applying DC electric field. • Electric dipole interaction formed by charged particles and electric double layer. Abstract The influence of the properties of a slurry on the flocculation behaviour of fine particles in water upon the application of a DC electric field was investigated. In addition, the mechanism whereby particles in water can be flocculated through the application of the DC electric field was clarified. The particle flocculation efficiency was determined for aqueous and non-aqueous slurries to which a DC electric field was applied, by measuring the change in the turbidity of the sampled slurry. It is shown that, for aqueous slurries, the particle flocculation could be enhanced by applying a DC electric field provided the particles carried a charge and were surrounded by an electric double layer. It was also found that there was no enhancement of the flocculation for those slurries for which pH = pH IEP , as well as for non-aqueous slurries using rapeseed oil as their solvent, in which case the particles were not charged. In addition, merely stirring the slurry (thus increasing the number of particle collisions) did not cause the particles to flocculate, although the particle flocculation could be enhanced by applying a DC electric field while stirring the slurry, thus maintaining a constant particle concentration. These findings lead to the conclusion that the enhancement of the particle flocculation in an aqueous slurry through the application of a DC electric field is caused by the charged particles and their counter ions in an electric double layer forming an electric dipole due to the deformation of the electric double layer, thus creating an electrostatic attractive force between the particles. [ABSTRACT FROM AUTHOR]

Highlights • Effect of DC electric field on oxygen reduction in TEL was studied. • Ions migration by DC electric field thermodynamically promotes oxygen reduction. • A more negative electrode potential by DC electric field boosts oxygen reduction. • A model for the effects of the DC electric field on oxygen reduction is proposed. Abstract The effect of direct current (DC) electric field and electrolyte layer thickness on oxygen reduction in simulated atmospheric environment were investigated using electrochemical measurements. The results show that the limiting diffusion current density (i lim) decreases with increasing the thin electrolyte layers (TELs) thickness but it increases with increasing the DC electric field intensity. The potential shifts negatively with the DC electric field. It is found that the DC electric field enables OH− ions to quickly migrate from the solution/electrode interface to the electrolyte layer. All these features promote the cathodic reduction process thereby enhancing the metal corrosion rate. [ABSTRACT FROM AUTHOR]

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The ionic wind effect is a well-known phenomenon in electric-field-assisted combustion in which the convective bulk flow can be modified by the collision of charged species with neutrals in the reaction region. This paper suggests an essential model based on 1D ionic transport equations to describe the ionic wind effect responsible for nonlinear responses of diffusion flame positions in a counterflow burner with DC voltage variations. The characteristics of ionized layers that substitute for counterflow diffusion flames were compared by applying the effects of one-way (unidirectional) and two-way (bidirectional) ionic wind models. The calculation results showed that the two-way ionic wind model was able to qualitatively predict the unique features of the flame positions in the present experiments and general trends in the electric current density reported in previous literature. The qualitative characteristics of the ionized layer can be classified into three regimes: (1) one-way ionic wind (OIW)-dominated regime, (2) transition regime, and (3) two-way ionic wind (TIW)-induced regime. The details are discussed in this article. The results of this study supported the importance of the two-way ionic wind effect for nonlinear responses of counterflow diffusion flames in DC electric fields. [ABSTRACT FROM AUTHOR]

Under dc electric field, pollution may be more easily deposited around insulator string caps and pins, distributing non-uniformly on its inner and outer parts, and presenting ring-like shape. dc Flashover tests of 7-unit XHP-160 insulator string were carried out. During the tests, the ring-shaped non-uniform pollution was simulated using solid-layer method by changing the ratio I/O of inner-to-outer surface salt deposit density (SDD) and radius (r) of the heavily polluted area (the inner part). On the basis of the test data, the effects of ring-shaped non-uniform pollution on dc flashover characteristics were studied. Then, the relative variation trend of flashover voltage, surface pollution layer resistance, and leakage current were discussed. Research results show that the ratio I/O affects the dc flashover performance of the insulator string. The flashover voltage increases with the increase of I/O. With the increase of the radius r, the flashover voltage will increase at first and then decrease. Under ring-shaped non-uniform pollution, surface pollution layer resistance of insulator will increase, which results in lower leakage current and higher flashover voltage. The results will be of certain value in providing references for outdoor insulation selection.

In this article, the effect of demulsification of diluteO/Wemulsion inDCelectric field and its mechanism are investigated. The results show that the demulsification process of dilute O/W emulsion is divided into three stages: water layer formation, re-emulsification with transverse diffusion and uplift-stabilization of O/W emulsion. There is a critical current in the electro-demulsification of dilute O/W emulsion. Some evidences confirm that O/W emulsion system with surfactant produces a surface tension gradient in the height direction during the stratification process. The critical current together with the surface tension gradient causes different demulsification processes and current variation for different emulsions. [ABSTRACT FROM AUTHOR]

The breakup behaviors of aqueous droplets with surfactant in oil under direct current (DC) electric field are investigated in this paper. Four different droplet breakup modes were observed, namely conical shape-conical jetting, ellipsoidal shape-conical jetting, ellipsoidal shape-filamentous breakup and cylindrical shape-filamentous breakup. The conversion of breakup modes was discussed with the electric capillary number ( Ca )-surfactant concentration ( C SDBS ) phase diagram and the droplet elongation process. The mechanism validated here is that the lobes appear in all breakup modes, and the liquid volume at the both ends of droplet differentiate the breakup modes under different conditions. Different from previous studies, the criterion of droplet breakup modes was proposed based on the interfacial dynamics instead of the bulk phase properties. By analogy with stress–strain relationship, it is found that the electrostatic pressure shows a linear relationship with droplet specific surface area during the droplet elongation process, and the slope K could be employed to identify different breakup modes. These findings are of great significance to the promotion and application of electric-induced droplet breakup. [ABSTRACT FROM AUTHOR]

In this work, the electrokinetic properties of asphaltene particles have been investigated. Micro-electrophoresis method by applying DC electric field, was utilized to different mixtures containing asphaltene to determine its electric charge. It was observed that in the case of using n-heptane and its mixture with toluene (heptol), the asphaltene particles were showed to be positively charged however for toluene itself, they expressed no tendency toward the electrodes. While it is expected that larger asphaltene aggregates carry higher electric charge, the results contradictorily showed that they are mainly governed by gravity rather than electro-static force and that “aggregation” reduces the charge density of asphaltene particles. Using a digital microscope equipped with image processing software, the average net electric charge of each asphaltene molecule was calculated to be 5 . 62 × 10 - 28 C m o l e c u l e or 3 . 51 × 10 - 9 ē m o l e c u l e . As this value is much less than 1ē, it can be concluded that asphaltene molecules do not possess intrinsic electric charge and the apparent charge is mostly induced through the medium, generated by rearrangement of asphaltene molecular structure. Thereafter, based on calculated charge and considering governing forces (gravity, friction and electric force), the electrophoretic mobility of asphaltene particles in dynamic mode was mathematically modeled and verified under different electric field intensities. The results illustrated satisfactory agreement with the obtained experimental data. Knowing the asphaltene electric charge, the magnitude of streaming potential can be calculated, subsequently the model will be able to predict the velocity ranges at which colloidal asphaltene flocculation is possibly avoided. Finally the effect of flow rate, electric potential and solvent composition was investigated on electrophoretic mobility. It was found that, the higher the fluid flow rate, the greater is the mobility. However, increasing the electric potential resulted in electrophoretic mobility reduction of asphaltene particles. Moreover, critical increase of electrophoretic mobility was observed for n-heptane contents of more than 50 wt.% in heptol, which refers to the onset point of asphaltene nano-aggregates. [ABSTRACT FROM AUTHOR]

The influence mechanism of a direct current (DC) electric field on the corrosion behaviour of zinc in a simulated industrial environment was studied by using weight loss measurement, electrochemical tests, XRD and SEM/EDS techniques. The results show that the corrosion rate of zinc increased with the increase of DC electric field intensities. The main corrosion products formed on the sample in ZnSO 4 solution are Zn(OH) 2, ZnO, Zn 5 (OH) 6 (CO 3 ) 2 and Zn 4 SO 4 (OH) 6 .5H 2 O. It was found that the DC electric field enables OH − and SO 4 2− ions to migrate from the solution/electrode interface to the upper layer of the solution quickly. Thus it can change the reaction site of the formation of Zn 4 SO 4 (OH) 6 .5H 2 O and can increase the quantity of the porous hexagonal plate Zn 4 SO 4 (OH) 6 .5H 2 O. All these features can promote the corrosion rate of zinc. [ABSTRACT FROM AUTHOR]

In this paper parallel flow velocity shear Kelvin-Helmholtz instability has been studied in two different extended regions of the inner magnetosphere of Saturn. The method of the characteristic solution and kinetic approach has been used in the mathematical calculation of dispersion relation and growth rate of K-H waves. Effect of magnetic field (B), inhomogeneity (P/a), velocity shear scale length ( A i ), temperature anisotropy ( T ⊥ / T | | ), electric field (E), ratio of electron to ion temperature ( T e / T i ), density gradient ( ε n ρ i ) and angle of propagation ( θ ) on the dimensionless growth rate of K-H waves in the inner magnetosphere of Saturn has been observed with respect to k ⊥ ρ i . Calculations of this theoretical analysis have been done taking the data from the Cassini in the inner magnetosphere of Saturn in the two extended regions of Rs ∼4.60–4.01 and Rs ∼4.82–5.0. In our study velocity shear, temperature anisotropy and magnitude of the electric field are observed to be the major sources of free energy for the K-H instability in both the regions considered. The inhomogeneity of electric field, electron-ion temperature ratio, and density gradient have been observed playing stabilizing effect on K-H instability. This study also indicates the effect of the vicinity of icy moon Enceladus on the growth of K-H instability. [ABSTRACT FROM AUTHOR]

The influx of a switching impulse during DC steady-state operations causes severe electrical stress on the insulation of HVDC cables. Thus, the insulation should be designed to withstand a superimposed switching impulse. All major manufacturers of DC cables perform superimposed switching impulse breakdown tests for prequalification. However, an experimental approach to study space charge dynamics in dielectrics under a switching impulse superposed on DC voltage has not been reported yet. This is because, unlike the DC stress, it is not possible to study the charge dynamics experimentally under complex stresses, such as switching impulse superposition. Hence, in order to predict and investigate the breakdown characteristics, it is necessary to obtain accurate electric field distribution considering space charge dynamics using a numerical approach. Therefore, in this paper, a numerical study on the switching impulse superposition was carried out. The space charge dynamics and its distribution within the dielectric under DC stress were compared with those under a superimposed switching impulse using a bipolar charge transport (BCT) model. In addition, we estimated the effect of a superimposed switching impulse on a DC electric field distribution. It was concluded that the temperature conditions of dielectrics have a significant influence on electric field and space charge dynamics.

The aim of this study was to provide more effective use of straw for energy production by co-firing wheat straw pellets with solid fuels (wood, peat pellets) under additional electric control of the combustion characteristics at thermo-chemical conversion of fuel mixtures. Effects of the DC electric field on the main combustion characteristics were studied experimentally using a fixed-bed experimental setup with a heat output up to 4 kW. An axisymmetric electric field was applied to the flame base between the positively charged electrode and the grounded wall of the combustion chamber. The experimental study includes local measurements of the composition of the gasification gas, flame temperature, heat output, combustion efficiency and of the composition of the flue gas considering the variation of the bias voltage of the electrode. A mathematical model of the field-induced thermo-chemical conversion of combustible volatiles has been built using MATLAB. The results confirm that the electric field-induced processes of heat and mass transfer allow to control and improve the main combustion characteristics thus enhancing the fuel burnout and increasing the heat output from the device up to 14% and the produced heat per mass of burned solid fuel up to 7%.

The breakup process of aqueous droplet with surfactant suspended in oil under direct current (DC) electric field is investigated in this paper. The characteristics of the breakup process, stretching, necking and breakup, are discussed quantitatively with the electric capillary number Ca and the dimensionless surfactant concentration C ∗ which is the ratio of surfactant concentration to the critical micelle concentration. The results show that the presence of surfactant reduces the steady deformation of droplet and significantly decelerates the stretching process, resulting from the redistribution of surfactant molecules within the oil/water interface. The law of droplet stretching process when C ∗ ≥ 1 indicates that the exchange of surfactant molecules between the bulk phase and the interface could not catch up with the increase of oil/water interfacial area. Ca and C ∗ count a great deal to the necking position and the daughter droplet size. The daughter droplet size decreases with the increase of surfactant concentration. These results provide a mechanistic framework to promote the electrocoalescence efficiency of oil/water emulsion and to the application of electric emulsification. [ABSTRACT FROM AUTHOR]

Experimental observations of scroll rings in excitable media have shown that, a dc electric field perpendicular to the plane of the ring can change the rate at which the ring shrinks, and in some cases it may cause the scroll ring to expand even though its filament tension is positive. Here we propose a kinematical model to account for these effects by extending the theory of dynamics of the free scroll ring to include the influence of electric field. In addition, some other significant results, for example, the electric field can slow down the drift velocity of the scroll ring along its symmetry axis and in some situations may reverse its drift direction, are also predicted by the kinematical model. Direct numerical simulations of a reaction–diffusion model are performed, and the obtained results are in quantitative agreement with the numerical solutions of the kinematical model. [ABSTRACT FROM AUTHOR]

In a semiconductor, optically excited electron-hole pairs, driven by a strong terahertz (THz) field, can recombine to create THz sidebands in the optical spectrum. The sideband spectrum exhibits a “plateau” up to a cutoff frequency of 3.17 U p , where U p is the ponderomotive energy. In this letter, we predict that the bandwidth of this sideband spectrum plateau can be broadened by applying an additional direct-current (DC) electric field. We find that if applying a DC field of E DC =0.2 E THz (where E DC and E THz are the amplitudes of the DC field and THz field, respectively), the sideband spectrum presents three plateaus with 5.8 U p , 10.05 U p and 16 U p being the cutoff frequencies of the first, second and third plateaus, respectively. This bandwidth broadening occurs because the DC field can increase the kinetic energy that an electron-hole pair can gain from the THz field. This effect means that the bandwidth of the sideband spectrum can be controlled flexibly by changing the DC field, thereby facilitating the ultrafast electro-optical applications of THz sideband generation. [ABSTRACT FROM AUTHOR]

The purpose of the current study is to enhance filterability of activated sludge by applying controlled DC electric field via perforated aluminum electrodes while providing an ineffective electric current on bacterial life. The studies were conducted in a 12 L laboratory scale cylindrical reactor. Recirculated activated sludge was provided from a full scale advanced biological wastewater treatment plant. The effects of exposure time (2, 5, 10, 15, and 30 min) and potential gradient (0.2, 0.5, 0.8, and 1 V/cm) are evaluated mainly by the results of specific resistance to filtration (SRF). The results also supported with variations in physical (pH, oxidation-reduction potential (ORP), and temperature) and soluble biochemical (chemical oxygen demand (COD), orthophosphate (PO4-P), and ammonia nitrogen (NH3-N)) properties of activated sludge. Electrical parameters (current density, energy consumption, and theoretical aluminum consumption) were studied to evaluate the most cost effective DC field vs. exposure time variation. Based on SRF experiments, energy consumption, and theoretical aluminum generation, optimal condition for enhancing filterability is recommended as 0.2 V/cm potential gradient applied for 5 min. [ABSTRACT FROM AUTHOR]

A small ethanol diffusion flame exhibited interesting characteristics under a DC electric field. A numerical study has been performed to elucidate the experimental observations. The flow velocity, chemical reaction rate, species mass fraction distribution, flame deformation and temperature of the flame in the applied DC electric field were considered. The results show that the applied electric field changes the flame characteristics mainly due to the body forces acting on charged particles in the electric field. The charged particles are accelerated in the applied electric field, resulting in the flow velocity increase. The effects on the species distribution are also discussed. It was found that the applied electric field promotes the fuel/oxidizer mixing, thereby enhancing the combustion process and leading to higher flame temperature. Flame becomes shorter with applied electric field and its deformation is related to the electric field strength. The study showed that it is feasible to use an applied DC electric field to control combustion and flame in small-scale. [ABSTRACT FROM AUTHOR]