Electric Field Strength Research Articles

Electrocombustion Characteristics of Iron Particle-Laden Methanol and Ethanol Droplets in a Direct Current Field

ABSTRACT This study investigates the electrocombustion and atomization behavior of single droplets (2.5 wt.% Fe) of ethanol (EtOH) and methanol (MeOH) fuels at the droplet scale. The experiments utilize a system with two opposing plate electrodes of varying distances (200, 150, and 100 mm) and both negative (↓) and positive (↑) polarizations within a vertical direct current (DC) electric field. The results show that for EtOH and EtOH/Fe droplets, the flame envelope changes to a spherical form at (↓) and (↑) polarizations at 100 mm plate spacing, while for MeOH and MeOH/Fe droplets, the flame envelope changes to a spherical form at (↓) and (↑) polarizations at 200, 150 and 100 mm plate spacing. Increasing electric field strength reduced the micro-explosion tendency of Fe particles in the flame region and the micro-explosion intensity of Fe particles was found to be higher in ethanol droplets than in methanol. No systematic relationship could be established between the electric field effect and the presence of Fe particles. The MeOH/Fe/150(↑) droplet exhibited the lowest extinction time of 1050 ms. The electric field fundamentally alters the secondary atomization process of the fuel droplets. Notably, the diameter regression of all MeOH-based fuel droplets deviates significantly from a linear relationship. The investigation into the combustion behavior of pure EtOH, MeOH, and their Fe-blended counterparts within an electric field environment suggests that MeOH and MeOH/Fe fuels exhibit superior combustion characteristics. However, further research is necessary to fully elucidate these findings.

Conceptual model of electrostatic non-ionizing air filter

Abstract Many infectious diseases such as SARS-CoV-2, rhinovirus, adenovirus, and influenza are transmitted through small respiratory droplets and various filtration systems are used to reduce the risk of airborne infection. Here, we develop a conceptual model of a filter, which is based on the electrostatic deposition of air droplets potentially containing pathogens. Within the model, we explore the effect of polarization of neutral spherical droplets moving in an air flow past cylindrical electrodes. The strength of electric field they produce is low enough to eliminate corona discharge and minimize air ionization, but high enough to capture the droplets. Based on the proposed model, we calculate the filtration efficiency in a quasi-continuous approximation. Also, we conduct numerical simulations of the deposition of respiratory droplets on a compact periodic array of cylindrical electrodes located at the nodes of a square lattice. The droplets with a radius of 10-20 μm pose the greatest threat in spreading the respiratory infections, and as we demonstrate, the proposed system is very effective in capturing droplets of this size, specifically, for a filter element with a width of about 5 mm, the filtration efficiency exceeds 90%.

DC voltage switching-based octuple-electrode microdevice for cell rotation and area-specific membrane capacitance measurement

Single-cell electrorotation plays an important role in the field of single-cell imaging and electric parameter measurement. However, reported cell rotation technology often adopts a quadruple-electrode structure and is excited by an AC signal. The distribution of electric field strength in the enclosed area is not uniform, and the rotation speed of the cells is related to the location in the area, so it is difficult to achieve uniformity of electric field distribution and the stationarity of rotation. This work proposes a DC voltage switching-based octuple-electrode microdevice for cell rotation and area-specific membrane capacitance measurements. This design can switch the DC voltages on each electrode periodically to produce a uniformly distributed rotating electric field. The rotation direction of the electric field can be realized by simply controlling the switching order of the analog switches. According to the theoretical single-cell model, the area-specific membrane capacitance of cells are determined through rotation movements. Simultaneously, based on simulation results, the rotation area is normalized to enhance the accuracy of the measuring electrical parameters. This study demonstrates the potential application of the proposed octuple-electrode DC voltage-based electro-rotation device for rapid, convenient, and cost-effective manipulation and electrical parameter measurement of single cells.

Apparent effective ionization coefficient in N2 and O2 gas mixtures determined with two separate methods

N2:O2 gas mixtures are important for applications of atmospheric pressure plasmas such as ozone production, air purification from VOCs and NOx and surface treatments. Fundamental parameters such as the effective ionization coefficient are inputs for theoretical plasma models for applications and must thus be accurately known. This work determined the apparent effective ionization coefficient in N2:O2 mixtures in a broad reduced electric field strength E/N range of 150–1200 Td with two separate methods and compared with BOLSIG+ calculations of reduced effective ionization coefficient. Additionally, the equilibrium distance required to establish a steady-state electron energy distribution was estimated from spatial profiles of optical emission.

AC-assisted microbially induced carbonate precipitation for sand reinforcement: An experimental study

Microbially induced carbonate precipitation (MICP) is a promising method for transforming natural soils into a rock-like material, enhancing soil strength and creating an environmentally friendly engineered geomaterial for load-bearing purposes. Applying alternating current (AC) for enhancing precipitation including changing the crystalline form of the calcium carbonate precipitates appeals as a possible solution to break the upper limit of the unconfined compressive strength (UCS) of bio-treated specimens. To assess the viability of AC-assisted MICP, a series of experiments were designed and conducted under various combination of conditions. The UCS, calcium carbonate content and permeability of the bio-fabricated specimens were obtained to evaluate the treatment effectiveness of AC-assisted MICP. The results demonstrate that the UCS of the sand column exhibits a linear increase with the applied voltage from 10 V to 30 V (i.e., electric field strength from 0.91 V/cm to 2.73 V/cm). The UCS value of the bio-specimen reaches 9.4 MPa after 3 treatments at a concentration of 1.00 mol/L, a voltage of 30 V, and a frequency of 100 Hz. With the assistance of an AC electric field, the adverse impacts caused by high chemical concentrations in the MICP process can be mitigated. We report that a more uniform distribution of the calcium carbonate content of the treated specimen is obtained under an optimal AC frequency of approximately 100 Hz in the current series of experiments. The induced ion vibration under the action of AC results in a change in crystalline form and an increase in the amount and uniformity of crystals precipitated on the surface of the soil grains, supported by X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images. For reference, the energy consumption and the cost for increasing the UCS of the bio-treated specimen to 5 MPa is estimated at 375.86 kWh and 676.55 HK$ per cubic meter, respectively. The findings from our experimental investigation and analysis provide compelling evidence that utilising AC electric field holds great potential for achieving an enhanced treatment effect of MICP and hence a stronger bio-soil.

Enhanced extraction of procyanidins from avocado processing residues by pulsed electric fields pre-treatment.

The waste generated by the global production of avocado (Persea americana Mill), which includes peels, seeds, and pulp, poses environmental challenges. The principles of circular economy offer a sustainable solution by valorizing this waste and transforming it into valuable products. This study investigates the potential of avocado by-products, particularly peels and seeds, as a source of procyanidins. Pulsed electric field (PEF) technology has been shown to increase the extraction yield of valuable compounds from food waste/losses. In our study, we optimized the PEF treatment of avocado peels and seeds for the extraction of procyanidins by using Box-Behnken designs with response surface methodology and desirability functions. The effects evaluated were the frequency (1,50,100 Hz), the electric field strength (0.8, 1.1, 1.5 kV/cm) and the number of pulses (100, 150, 200) for avocado peel, while for the avocado seeds were the frequency (50, 100, 150 Hz), the electric field (0.6, 0.7, 0.8 kV/cm) and the total operating time (1, 5, 10 s). Our study showed that the procyanidin content measured by HPLC-FLD significantly increased in PEF-pretreated avocado peel and seeds. The optimized treatment conditions include a frequency of 50 Hz, an electric field strength of 1.31 kV/cm, and 175 electric pulses for the avocado peels, resulting in a procyanidin content of 9798.32 ± 103.83 μg CE/g d.w. For avocado seeds, the optimal conditions include a frequency of 100 Hz, an electric field strength of 0.75 kV/cm, and total operating time of 5.5 s, resulting in a procyanidin content of 21103.12 ± 234.76 μg/g d.w. The precision and validity of the mathematical models confirmed the reliability of these optimal conditions. These results emphasize the potential of PEF technology for the extraction of procyanidin from avocado waste and contribute to environmentally friendly extraction techniques in the food industry.

Rapid 3D printing of electro-active hydrogels

Electroactive hydrogels (EAH) have gained prominence for their unique ability to change shape or size under an electric field, finding applications in biosensors and soft actuators. This study focuses on a tunnelable EAH tailored for high-resolution 3D printing via the micro continuous liquid interface production (µCLIP) process. The resin formulations mainly involve acrylic acid (AA) and 4-hydroxybutyl acrylate (4-HBA). AA, with its carboxyl groups, introduces electroactuation, generating osmotic pressure in the hydrogel matrix. This results in swelling, inducing bending towards the cathode, accentuating the material’s responsiveness. In contrast, 4-HBA offers mechanical resilience, providing an elastic backbone, and ensuring the hydrogel’s applicability. Our results illustrate the hydrogel’s strength, flexibility, and bending capabilities across varied compositions and electric field strengths. Notably, the µCLIP process enabled the 3D printing of our EAH into sophisticated structures, like the lattice. The combination of AA’s electro-responsive traits with 4-HBA’s durability has birthed a material with vast practical implications. This study provides extended potential breakthroughs in soft robotics, wearable electronics, and medical devices, marking a significant stride in the realm of electroactive materials.

Electric field components within a micro-scaled DBD measured by Stark shifting and splitting of helium lines

Abstract Atmospheric pressure dielectric barrier discharges (DBDs), such as the micro cavity plasma array (MCPA), have emerged as promising technologies for the conversion of volatile gases. These conversion processes’ effectiveness can be enhanced by integrating catalytically active surfaces. To deepen the understanding of the plasma-catalyst interaction, it is crucial to study the transport dynamics of charged species to the catalytic surface, which, due to collisions with neutrals, also directly affects the transport of reactive species to the catalyst. Thereby the transport of the charged species is in particular influenced by the electric field perpendicular to the catalytic surface. However, experimental data on the component-wise electric field strength within SDBDs are rare. To address this issue, we performed polarized optical emission spectroscopy on the shifting and splitting of the allowed 492.19 nm (1D → 1P0) and forbidden 492.06 nm (1F0 → 1P0) helium line pair. This diagnostic approach requires a non-radially symmetric geometry, which leads to an adapted reactor design of the MCPA allowing the side-on observation of the discharge. The discharge operates in pure helium at atmospheric pressure, utilizing a triangular excitation voltage with a frequency of 15 kHz and an amplitude of 600 V. We performed phase-resolved measurements of the electric field components with a temporal resolution of 1 µs. Our results revealed an electric field strength of approximately 22 kV cm−1 for the component perpendicular to the dielectric surface, while the component parallel to the dielectric surface is about 5 kV cm−1 larger during the decreasing potential phase of the applied voltage.

Simulation of the pulsed streamer discharge in water considering the effect of hydrostatic pressure

Streamer discharge is a very complex multi-scale and multi-physics coupling process, and there is no accurate model that can describe its development. In this paper, a two-dimensional axisymmetric fluid model is established in COMSOL to simulate and study the effects of the applied voltage amplitude, the discharge gap distance, the rising edge of pulse voltage, and hydrostatic pressure on the development of the positive streamer discharge at a needle-plate electrode in water under a nanosecond pulse voltage. The results show that increasing the voltage amplitude, decreasing the pulse rise time, and narrowing the discharge gap all increase the electric field strength of the streamer, thereby affecting the electron density of the plasma channel, among which changing the discharge gap has the greatest effect on the electron density. And under the gap of 3 mm, the peak electron density can reach 3.76 × 1023 m−3; if the discharge gap is narrowed to 1 mm, the peak electron density is reduced to 1.20 × 1023 m−3. In addition, hydrostatic pressure and water molecule spacing are closely linked. Increasing the hydrostatic pressure decreases the electric field strength and the peak electron density in the plasma channel, and its effect on the peak electron density saturates with increasing hydrostatic pressure.

Tip-induced local Fermi level alignment: A Stark shift in vacuum level in scanning tunneling microscope configurations

Electric fields in the junction of a scanning tunneling microscope (STM) are generally considered to have a negligible impact on the vacuum level (VL) of materials. We employed field emission resonance (FER) in the STM, combined with the triangular potential model, to measure the VL of the Ag(100) surface under varying electric currents. Unexpectedly, our results reveal that the VL exhibits a linear positive energy shift with increasing electric field strength. We suggest that this Stark shift in the VL arises from local Fermi level alignment induced by the STM tip. Additionally, we examined the VL of Ag islands grown on Cu(111) and Au(111) surfaces under different currents. Despite the Ag island having a lower work function than the Cu(111) and Au(111) surfaces, the energy shift in the VL with respect to the electric field on the Ag island is almost identical to that on the substrate under the same tip structure. This suggests that the Stark shift of the VL is insensitive to the work function. These findings are crucial for utilizing FER to measure local work function variations on surfaces, as the measured value is not influenced by the STM tip structure or the tunneling current, both of which can alter the electric field.

Improvement in uniformity of co‐linear pulsed electric field treatment chamber by sub‐electrodes and its optimization

AbstractThe uniformity of performance parameters such as electric field and temperature for a co‐linear pulsed electric field (PEF) processing system is one of main factors affecting the processing effect and quality of liquid food. We have proposed a co‐linear PEF treatment chamber configuration with sub‐electrodes to improve the uniformity and processing efficiency. We have first examined how the position of the sub‐electrodes alone affects the uniformity of the performance parameters. Then, we have investigated the variation of the uniformity while changing simultaneously the electrode radius, inter‐electrode gap, and position of sub‐electrodes. As a result, we have found that the most uniform field could be obtained when the electrode radius is 5.5 mm, the inter‐electrode gap is 15 mm, and the sub‐electrodes situate at the middle of the chamber. In this chamber, the region between 95% and 105% of the average electric field covers 83%, which shows much improvement compared to the formers' results, 69.5% and 76%, respectively. Also, the optimal treatment chamber provides greater average electric field under the same voltages as the voltages reported by the formers.Practical applicationsA novel treatment chamber with sub‐electrodes is proposed for pulsed electric fields food processing. The improved treatment design was obtained by changing position of sub‐electrodes, inner radius of electrodes and distance between electrodes. The more uniform electric field was obtained in treatment region. The temperature distribution was more uniformed by increasing flow rates and uniformed electric field strength. The treatment throughput was increased by sub‐electrodes.

Online control of educational results of the unit “Electricity” in the conditions of blended learning

Abstract The article describes the technology of online control of educational results of the unit “Electricity” in the conditions of blended learning. It was determined that during the online stages of studying unit “Electricity”, reverse communication is an urgent issue when receiving information in a distance format, and online control is designed to support the organization of a modern training session. Three topics have been singled out in the unit, in the context of which it is appropriate to develop control measures. Topic I “Electric Field in a Vacuum” focuses on the study of electric field strength, potential, the relationship between strength and potential, the electric dipole, and the circulation and flow of an electric field. Topic II “Electric Field in a Substance” involves the study of the electric field in dielectrics and conductors in an electric field. Topic III “Electric Current” includes general laws of electric current, electric circuit, current in a circuit with a capacitor, and current work and power. There are outlined the different types of tests: graphical, calculation, animated, audio that form the means of online control in the context of the outlined unit. The developed technology of online control of educational results of the unit “Electricity” provides for an organic combination of the presentation of educational materials with control measures. The research methodology involved the analysis and synthesis of scientific, pedagogical, methodological sources and empirical methods, as well as the analysis of the obtained results. Before the introduction of the developed technology and after the completion of the experimental work, a study was conducted, which included an analysis of the quality of knowledge when studying the specified topic. The obtained results before and after the experiment were tested using the Pearson statistical test χ 2.

Enhancing the specific activity of 3α-hydroxysteroid dehydrogenase through cross-regional combinatorial mutagenesis

3α-Hydroxysteroid dehydrogenase (3α-HSD) from Comamonas testosteroni is widely used in clinical settings to measure serum total bile acid levels. However, its low enzymatic activity leads to high operational costs. In this study, we employed a combinatorial mutagenesis approach to systematically identify potential key mutation sites within the enzyme. The enzyme molecule was segmented into distinct regions, and a comprehensive strategy integrating substrate pocket engineering, binding energy calculations, and deep learning techniques was used. Through experimental verification, single-point mutants from the mutation library with enhanced enzymatic activity by at least 1.5-fold were identified. Through iterative combinatorial mutations of them, the optimal mutant H119A/R201G/R216L was obtained. This mutant exhibited a specific activity of 34.18 U/mg towards deoxycholic acid, representing a 6.85-fold increase over the wild-type (WT) enzyme. Additionally, the optimal temperature of the mutant increased from 35 °C to 40 °C, and its turnover number and catalytic efficiency increased by 6.4-fold and 9.4-fold, respectively. Quantum mechanics/molecular mechanics (QM/MM) calculations indicated that the energy barrier of the dehydrogenase reaction was reduced in the H119A/R201G/R216L mutant compared to that of the WT enzyme. Specifically, the R201G mutation significantly reduced the electric field strength along the 3α-hydroxyl group, facilitating its deprotonation. This study provides insights into enhancing enzymatic efficiency through strategic mutagenesis and elucidates mechanistic changes that optimize enzyme performance for clinical and biotechnological applications.

Local and nonlocal conditions for electron runaway in a gas gap with a conical cathode with a variable opening angle

The conditions for the generation of runaway electrons in an air gap are compared at different degrees of inhomogeneity of the electric field distribution provided by varying the opening angle of the conical cathode: in the range 40°–120° in experiments and 0°–180° in calculations. It is demonstrated that, in a weakly inhomogeneous electric field (according to the proposed classification, this corresponds to cones with angles greater than the Taylor angle of 98.6°), the runaway condition has a local character. The transition of free electrons into the runaway mode is determined by the local distribution of the electric field near their starting point—the tip of the cone. The local electric field strength must exceed a threshold value comparable to the strength critical for the runaway of electrons in a uniform field. In a strongly inhomogeneous field (cones with angles less than 98.6°), this condition is not sufficient for electrons to run away throughout the gap. Electrons accelerating in the near-cathode region may begin to slow down in a weak field at a distance from the cathode. In this case, the runaway condition becomes nonlocal. It is determined by the dynamics of electrons in the entire gap, primarily in the near-anode region, and reduces to the requirement that the potential difference applied to the gap exceeds a certain threshold value.

Redistribution of Electric Field Strength in Insulation Using Electrets

Redistribution of Electric Field Strength in Insulation Using Electrets

High sensitivity measurement of ULF, VLF, and LF fields with a Rydberg-atom sensor.

Fields with frequencies below megahertz are challenging for Rydberg-atom-based measurements, due to the low-frequency electric field screening effect caused by the alkali-metal atoms adsorbed on the inner surface of the container. In this paper, we investigate electric field measurements in the ultralow frequency (ULF), very low frequency (VLF), and low frequency (LF) bands in a Cs vapor cell with built-in parallel electrodes. With optimization of the applied DC field, we achieve high-sensitive detection of the electric field at frequencies of 1 kHz, 10 kHz, and 100 kHz based on the Rydberg-atom sensor, with the minimum electric field strength down to 18.0 μV/cm, 6.9 μV/cm, and 3.0 μV/cm, respectively. The corresponding sensitivity is 5.7 μV/cm/Hz1/2, 2.2 μV/cm/Hz1/2, and 0.95 μV/cm/Hz1/2 for the ULF, VLF, and LF fields, which is better than a 1-cm dipole antenna. Besides, the linear dynamic range of the Rydberg-atom sensor is over 50 dB. This work presents the potential to enable more applications that utilize atomic sensing technology in the ULF, VLF, and LF fields.

Acidic phosphonium-based ionic liquid encapsulated on titania particles with enhanced electrorheological response

Research on electrorheological (ER) fluids has led to significant advancements in the development of smart materials that adjust their viscosity in response to applied electric fields. This study focused on synthesizing titania ionogel-based particles (TiO2-IL) using an environmentally friendly sol-gel process involving tetrabutoxy-titanium (TBT) combined with an ionic liquid (IL), specifically 11-carboxyundecyl-triphenyl-phosphonium bromide. The successful incorporation of the IL into the TiO2 particles was confirmed through thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and zeta potential analysis. The electrorheologial properties of TiO2-IL ionogel suspension in silicone oil were compared with those of pure TiO2 suspension. The addition of the ionic liquid (IL) significantly enhanced the electrorheological (ER) properties of the fluid, achieving a shear stress of approximately 1340Pa at an electric field strength of 5kV/mm. The fluid also exhibited excellent reversibility and a rapid response to changes in the electric field, which is attributed to the higher polarizability by the IL. Furthermore, the study observed low current density during operation, which helps maintain the fluid’s integrity and longevity under high electric fields. The fluids demonstrated stable ER effect across a temperature range of 40 to 70 ℃ and a reasonable sedimentation stability of around 80%. These characteristics, combined with the moderate conditions for particle preparation, make the TiO2-IL fluid a promising candidate for ER applications.

Electric Field Features and Charge Behavior in Oil-Pressboard Composite Insulation under Impulse Voltage

Oil-pressboard/paper insulation materials are essential in transformers for ensuring their safe and stable operation, primarily due to their roles in spatial electric field distribution and charge migration mechanisms. Current spatial distribution analyses rely on computational methods that lack empirical validation, particularly for oil-pressboard/paper composites. This study leverages the principles of the Kerr electro-optic effect to develop a rapid measurement platform for electric fields within oil-pressboard/paper insulation under impulse voltage conditions, which measures the spatial electric field characteristics using Cu-Cu and Al-Al electrodes under various scenarios: with asymmetric and symmetric pressboard coverage and different numbers of insulating paper layers. Findings indicated: (1) In asymmetric pressboard models, Cu-Cu electrodes exhibit a consistent peak electric field of approximately 16 kV/mm, while Al-Al electrodes show peak values of 18.13 kV/mm and −14.98 kV/mm. Charge density patterns are similar, with Cu-Cu at about 68 μC/m2 and Al-Al at 11.2 μC/m2 and −124.8 μC/m2. (2) Symmetric models present consistent peak electric fields and charge densities for both polarities. (3) Increasing insulating paper layers elevates electric field strengths. Both electrodes show the similar peak field of about 17 kV/mm with differing paper layers due to higher charge injection from the Al electrode. (4) Utilizing the Schottky effect and field emission principles, the study clarifies charge generation and migration mechanisms. These insights could provide a theoretical foundation for designing and verifying oil-pressboard/paper insulation structures in transformers.

Моделирование суточной вариации атмосферного электрического поля в турбулентном приземном слое

An electrodynamic model of the electric field dynamics behavior in the atmospheric surface layer due to the action of local factors is presented. The model was obtained by reducing the differential equations system of the electrode effect to the so-called total current equation, which is a second-order equation of parabolic type, considered in a two-dimensional space-time region. The total current equation allows us to connect the set of main factors influencing on the atmospheric surface layer electric field state: conduction current, turbulent current and current arising as a result of convective processes in the atmosphere with the so-called total current in the nearground layer, reflecting changes in the ionospheric potential. The described method provides significant advantages in research, since within the framework of one model it allows the formulation of various problems of electrodynamics of the surface layer and a comparative analysis of the influence on the behavior of the electric field in the surface layer of both individual factors and their combinations. Based on meteorological data at the Peak Cheget mountain station in the Elbrus region, a daily variation in the values of the turbulent diffusion coefficient was constructed. The resulting analytical dependence was used to solve the equation for the total current in the surface layer, provided that it is constant at the upper boundary of the turbulent electrode layer. Solutions obtained by the Fourier method describe the daily variation of the electric field strength depending on the degree of turbulent mixing in the atmosphere. The appearance of a time shift in daily extrema, a change in their amplitude, and the appearance of additional extrema depending on the elec-tric field values have been established. All of these effects are comparable to the global unitary variation and increase with increasing electric field.

Carrier dynamic identification enables wavelength and intensity sensitivity in perovskite photodetectors

Deciphering the composite information within a light field through a single photodetector, without optical and mechanical structures, is challenging. The difficulty lies in extracting multi-dimensional optical information from a single dimension of photocurrent. Emerging photodetectors based on information reconstruction have potential, yet they only extract information contained in the photoresponse current amplitude (responsivity matrix), neglecting the hidden information in response edges driven by carrier dynamics. Herein, by adjusting the thickness of the absorption layer and the interface electric field strength in the perovskite photodiode, we extend the transport and relaxation time of carriers excited by photons of different wavelengths, maximizing the spectrum richness of the edge waveform in the light-dark transition process. For the first time, without the need for extra optical and electrical components, the reconstruction of two-dimensional information of light intensity and wavelength has been achieved. With the integration of machine learning algorithms into waveform data analysis, a wide operation spectrum range of 350–750 nm is available with a 100% accuracy rate. The restoration error has been lowered to less than 0.1% for light intensity. This work offers valuable insights for advancing perovskite applications in areas such as wavelength identification and spectrum imaging.