Discharge Mechanism Research Articles

Tuning Electrostatic Interactions of Colloidal Particles at Oil-Water Interfaces with Organic Salts.

Monolayers of colloidal particles at oil-water interfaces readily crystallize owing to electrostatic repulsion, which is often mediated through the oil. However, little attempts exist to control it using oil-soluble electrolytes. We probe the interactions among charged hydrophobic microspheres confined at a water-hexadecane interface and show that repulsion can be continuously tuned over orders of magnitude upon introducing nanomolar amounts of an organic salt into the oil. Our results are compatible with an associative discharging mechanism of surface groups at the particle-oil interface, similar to the charge regulation observed for charged colloids in nonpolar solvents.

Discharge behavior of spherical and rock chip mucks by screw conveyors in TBM: Physical model experiments and DEM simulations

The discharge of muck through a screw conveyor system plays a crucial role in ensuring safe and cost-effective tunneling with earth pressure balance tunnel boring machines (EPB-TBM). However, the discharge mechanism of chip-type rocky mucks through a screw conveyor has not been well examined. Therefore, this study investigates the discharge behavior of rock chips through a screw conveyor by using a 3D discrete element model (DEM). Numerical simulations are conducted with rock chip particles of various sizes, as well as spherical particles, while varying the inclination angle, screw pitch length, and rotational speed of the screw conveyor. The simulation results show that the relative size between the muck particles and pitch has a significant effect on the discharge rate, and an optimal ratio of pitch to flight diameter is suggested. The particle-level analysis reveals distinctive particle discharge paths and a velocity distribution of muck particles along the screw axis. The study proposes the ratio of the screw pitch to the maximum particle size as the primary design parameter to predict the discharge rate. This is because large particles play a critical role in determining the discharge rate. The study highlights the usefulness of 3D DEM-based simulation as a tool to investigate discharge behavior of particulate materials through a screw conveyor. Moreover, it advances our understanding of rock chip-type muck discharge behavior during TBM excavation, providing guidance for screw conveyor design and feedback during TBM operation.

Direct etching of nano/microscale patterns with both few-layer graphene and high-depth graphite structures by the raster STM electric lithography in the ambient conditions.

The development of raster STM electric lithography has enabled the etching of nano/microscale patterns on both few-layer graphene (FLG) and high-depth graphite structures on the bulk HOPG substrates under ambient conditions. This approach utilises a nanoscale probe tip as a machining tool to directly fabricate conductive sample surfaces without the need for resists or masks. Compared to conventional nano/micro machining methods, the capability of ultraaccurate fabrication of nanoscale patterns using this technique is unmatched. The resulting FLG structures exhibit ultrasmooth flat bottoms and uniformly controlled depths ranging from 0.34 to 3.0nm (less than 10 layers). This work represents a significant advancement as it demonstrates the perfect etching of FLG structures in designated nano/microscale regions using raster STM electric lithography in the constant current mode, which reaches the limitation of top-down manufacturing techniques. Additionally, raster STM electric lithography in the constant height mode can directly etch high-depth structures (up to ∼100nm). The geometric shape and number of layers of the etched graphene structures determined by either local anodic oxidation (LAO) or the electric discharge (ED) mechanism. The LAO mechanism results in less debris and smoother edges compared to the ED mechanism, which is caused by the random electrical discharge between the tip and the sample. The well-controlled raster STM electric lithography technique is believed to be a promising and facile approach for constructing nano/microscale graphene-based devices.

Wind-modulated groundwater discharge along a microtidal Arctic coastline

Groundwater discharge transports dissolved constituents to the ocean, affecting coastal carbon budgets and water quality. However, the magnitude and mechanisms of groundwater exchange along rapidly transitioning Arctic coastlines are largely unknown due to limited observations. Here, using first-of-its-kind coastal Arctic groundwater timeseries data, we evaluate the magnitude and drivers of groundwater discharge to Alaska’s Beaufort Sea coast. Darcy flux calculations reveal temporally variable groundwater fluxes, ranging from −6.5 cm d−1 (recharge) to 14.1 cm d−1 (discharge), with fluctuations in groundwater discharge or aquifer recharge over diurnal and multiday timescales during the open-water season. The average flux during the monitoring period of 4.9 cm d−1 is in line with previous estimates, but the maximum discharge exceeds previous estimates by over an order-of-magnitude. While the diurnal fluctuations are small due to the microtidal conditions, multiday variability is large and drives sustained periods of aquifer recharge and groundwater discharge. Results show that wind-driven lagoon water level changes are the dominant mechanism of fluctuations in land–sea hydraulic head gradients and, in turn, groundwater discharge. Given the microtidal conditions, low topographic relief, and limited rainfall along the Beaufort Sea coast, we identify wind as an important forcing mechanism of coastal groundwater discharge and aquifer recharge with implications for nearshore biogeochemistry. This study provides insights into groundwater flux dynamics along this coastline over time and highlights an oft overlooked discharge and circulation mechanism with implications towards refining solute export estimates to coastal Arctic waters.

A xenon collisional-radiative model applicable to electric propulsion devices: III. Determination of the ionization fraction in low-temperature xenon plasma by using ionic and atomic 6p lines

The ionization fraction is a key figure of merit for optimizing the performance of plasma device. This work presents an optical emission spectroscopy (OES) method to determine the ionization fraction in low-temperature xenon plasma. The emission line-ratio of xenon ionic and atomic 6p–6s transitions is used in this method. A comprehensive collisional-radiative model developed in our previous work is employed to describe the relationship between the line-ratios and the plasma parameters. It is found that some special line-ratios have a sensitive relationship to the ionization fraction, e.g. the ratio of the 460.30 nm line and 828.01 nm lines. These line-ratios are selected for the diagnostic method. The method is demonstrated in a magnetized discharge chamber. The axially-resolved emission spectra of the ionization chamber are measured, and from those the ionization fraction along the chamber axis is determined via the OES method. The axially-resolved ionization fraction is found to be dependent on the magnetic field and agrees well with those obtained from a Langmuir probe. In the experiment, the probe is overheated under some conditions, possibly due to the bombardment by energetic particles. In this case, no results can be obtained from the probe, while the OES method can still obtain reasonable results. Combined with optical tomography and spectral imaging technology, the OES method can also provide the spatial distribution of the ionization fraction, which is needed for revealing the discharge mechanisms of plasma devices.

Corollary discharge function in healthy controls: Evidence about self-speech and external speech processing.

As we speak, corollary discharge mechanisms suppress the auditory conscious perception of the self-generated voice in healthy subjects. This suppression has been associated with the attenuation of the auditory N1 component. To analyse this corollary discharge phenomenon (agency and ownership), we registered the event-related potentials of 42 healthy subjects. The N1 and P2 components were elicited by spoken vowels (talk condition; agency), by played-back vowels recorded with their own voice (listen-self condition; ownership) and by played-back vowels recorded with an external voice (listen-other condition). The N1 amplitude elicited by the talk condition was smaller compared with the listen-self and listen-other conditions. There were no amplitude differences in N1 between listen-self and listen-other conditions. The P2 component did not show differences between conditions. Additionally, a peak latency analysis of N1 and P2 components between the three conditions showed no differences. These findings corroborate previous results showing that the corollary discharge mechanisms dampen sensory responses to self-generated speech (agency experience) and provide new neurophysiological evidence about the similarities in the processing of played-back vowels with our own voice (ownership experience) and with an external voice.

Accelerated verification method for the reliability of the motor drive mechanism of the corn precision seed-metering device

The current reliability analysis of the motor drive mechanism of the corn precision seed-metering device has yet to be validated by accelerated testing. Furthermore, the bench test used for verification does not consider the effect of vibration loads on the seeder during field operation. Therefore, this paper proposes an accelerated reliability verification method for the motor drive mechanism of the corn precision seed-metering device. Firstly, reliability theory is used to analyze the importance degree of motor drive system subcomponents. Then, various field tests were carried out to collect vibration and temperature rise data, to analyze the effect of field vibration on the motor drive mechanism, and to propose the vibration influence parameter k. Finally, an indoor test bench was set up, the formula of the acceleration factor A was modified, and accelerated verification tests on 96 motors were carried out to verify the method's accuracy. Reliability analysis showed that the motor’s importance degree was 79.31%, and the Hall switch was 19.78%. The field tests showed that the mean values of the vibration influence parameter k for the four seeding conditions (different seeding speeds) were 0.155, 0.186, 0.207 and 0.228. The accelerated tests showed that the absolute error between the accelerated verification test and the reliability analysis was 1.1% and 3.3% in importance degree and average life, respectively. This paper provided a solution for the reliability study and accelerated verification of the corn electric drive seed discharge mechanism.

Partial Discharge Characteristics and Mechanism of Medium Voltage Power Cable Defects under Different Voltage Stresses

Off‐line partial discharge (PD) diagnosis, which requires an additional power supply has been accepted as an essential step in ensuring the integrity of power cable systems during commissioning testing. Many types of energizing voltage sources (e.g., alternating current resonance, damped alternating current, very low frequency [VLF] sine, and VLF‐cosine rectangular) have been developed, which are used in practice. However, choosing the optimal energizing voltage waveforms for PD testing is still controversial because their capability to motivate PD activities is still unclear. Accordingly, this paper compares the PD ignition capacity of the aforementioned power sources on six well‐designed PD defects in real cable joints. The influence of test voltage frequencies and waveforms are verified. The results show that the PD inception voltage and PD magnitudes in the cable joint defects do not change significantly as a function of the sinusoidal voltage frequency and the VLF‐cosine rectangular voltage exhibits excellent PD ignition capability with a low PD inception voltage and large PD magnitude. Moreover, the dynamic behavior of space charge in a PD defect caused by a gap is analyzed in order to explain the obtained results. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

DC negative corona discharge characteristics of the needle-plate electrode under different air pressures

Because of the low normal atmospheric pressure and frequent, more severe corona discharges in high-altitude regions. The electromagnetic environment problems caused by the corona discharge restrict the line design in high-altitude areas. The variance in the law of negative DC corona characteristics under different air pressure conditions is derived using an artificial climate tank with adjustable air pressure. The characteristics of the negative DC needle-plate corona discharge were measured experimentally. The negative DC corona discharge pulses at 89.4 kPa–56.04 kPa were obtained, and the characteristics of the current pulses were statistically examined. The study of the mechanism of the DC corona discharge can benefit from the research findings as essential reference data.

Influence of Humidity and Salinity on the Transformation of Positive Corona Discharge Modes in Rod–Plane Gap

In this paper, the positive corona discharge in rod-plane gap was measured by non-inductive resistance, photomultiplier and ultraviolet imager. With the increase of applied voltage, different positive corona discharge modes are distinguished according to the difference of optical and electrical characteristics. The positive corona discharge develops from streamer discharge to glow discharge at low humidity, and the discharge of water molecules in air can be detected before streamer discharge when the relative humidity is higher than 80%. Humidity has little effect on the inception voltage of streamer discharge, while the inception voltage of glow discharge increases with the humidity. As for the positive corona discharge in salty air, the streamer discharge will never develops into the glow discharge but develops directly to a spark if the air humidity is somewhat high. The physical mechanism of positive streamer discharge and glow discharge are analyzed, and the evolution of space charge distribution during positive corona discharge are obtained by simulation. The glow discharge is characterized by the presence of negative ion sheath around the anode. The increase of humidity and salinity in air reduces the migration rate of negative ions, which is not conducive to the establishment of glow discharge.

Buharlaştırılmış folyo aktüatör kaynağı prototip imalatı ve uygulamaları risk analizi

This study was conducted to examine risk levels for Vaporizing Foil Actuator Welding (VFAW) prototype manufacturing and applications. A risk analysis was carried out by using the L-type matrix method to detect hazards and risks in newly developing VFAW applications. 60 risks were identified for VFAW, 37 of which were high and 23 were moderate. In order to reduce the risk and occupational accidents to the lowest possible level; a measuring instrument that can continuously monitor current and voltage values, a remote detonation system and a discharge mechanism have been added to the prototype system. Thanks to the measures taken the situations that may result in serious accidents, fire, explosion, loss of limb and even death that may occur during the experiment have been brought under control and VFAW applications have been made safer.

Universal lower bound on orbital periods

It is proved, using the curved line element of a spherically symmetric charged object in general relativity and the Schwinger discharge mechanism of quantum field theory, that the orbital periods T_{infty } of test particles around central compact objects as measured by flat-space asymptotic observers are fundamentally bounded from below. The lower bound on orbital periods becomes universal (independent of the mass M of the central compact object) in the dimensionless ME_{text {c}}gg 1 regime, in which case it can be expressed in terms of the electric charge e and the proper mass m_{e} of the lightest charged particle in nature: T_{infty }>{{2pi ehbar }over {sqrt{G}c^2 m^2_{e}}} (here E_{text {c}}=m^2_{e}/ehbar is the critical electric field for pair production). The explicit dependence of the bound on the fundamental constants of nature {G,c,hbar } suggests that it may reflect a fundamental physical property of the elusive quantum theory of gravity.

Principal antifungal factors and underlying mechanisms of dielectric barrier discharge plasma against Penicillium expansum spores as well as its application in kiwi-fruit juice

The objective of this work was to investigate the main antifungal factors and mechanisms of dielectric barrier discharge (DBD) plasma against Penicillium expansum spores. The application in kiwi-fruit juice was also studied. The results showed that 240 s was adequate for an about 6.0 log10 reduction of survival spores in kiwi-fruit juice after plasma treatment at 18 kV. DBD plasma treatment resulted in slight changes in pH, total phenolics, and color parameters of kiwi-fruit juice, but did not affect the total soluble solid and vitamin C contents. Among the longer-lived species generated by DBD plasma, NO2− was demonstrated to be related with the inactivation of P. expansum spores, but not considered as the important agent. Additionally, short-lived species (such as ∙OH, O2∙−, and 1O2) were confirmed to exist in the plasma-water system by electron spin resonance spectroscopy. Thereinto, O2∙− and 1O2 contributed the most to the inactivation. Both species caused the morphologic alteration, membrane disruption, intracellular substance leakage, and DNA damage of spores. In conclusion, DBD plasma can effectively inactivate P. expansum spores in kiwi-fruit juice, which is mainly due to the disruption of cell membrane and DNA damage induced by O2∙− and 1O2 derived from DBD plasma.

Non-thermal plasma actuator mechanism in interaction with fluid flow structure for aeronautical flow control

Plasma actuators generated by surface dielectric barrier discharge are developed for controlling flow in aeronautics applications. This research studies the simulation of cold plasma discharge at atmospheric pressure coupled with compressible fluid dynamics using COMSOL Multiphysics 5.4. Modeling of dielectric barrier discharge in air at high voltages is carried out in two dimensions. The development of electric field and space charge density are discussed in several cases to determine the discharge regime. Non-thermal plasma generates tangential ionic winds at the surface during corona discharge. The results are validated by the experimental results of the literature. The maximum electric wind velocity above the actuator grows linearly with the applied voltage, and simultaneously, the horizontal extension of the discharge grows with the applied voltage. The induced electrohydrodynamic force augments with the applied voltage amplitude, reaching saturation at higher voltages. Moreover, as the voltage rises, the discharge becomes filamentary, inducing a higher number of streamer pulses. Hence, the power consumption discharge increases abruptly as the voltage rises. In addition, the efficiency increases at higher voltage amplitudes and with the dielectric thickness. Our findings give a clear description of physical atmospheric plasma parameters in the surface discharge mechanism and the efficiency of the actuator plasma.

Ex situ TEM observations of the SnB2O4 glass electrode in all-solid-state lithium-ion batteries after charge–discharge process

As an environmentally friendly Pb-free material, SnO–B2O3 glass is considered a next-generation negative-electrode active material for all-solid-state lithium-ion batteries. Using SnB2O4 (50SnO·50B2O3) as a negative-electrode active material, the all-solid-state cells exhibit a high initial discharge capacity of approximately 950 mAh g−1. In this study, the microstructures of the SnB2O4 glassy electrode composites are investigated to clarify the charge–discharge behavior and charge–discharge mechanisms of the SnB2O4 glassy electrode composites using transmission electron microscopy (TEM). Here, ex situ TEM observations capture Sn and Li–Sn alloy nanocrystallites in the amorphous matrix. Li+ is incorporated into Sn, and Li–Sn alloy nanocrystallites are formed after initial lithiation. Further, Li+ is extracted from Li–Sn alloys to form Sn nanocrystallites after initial delithiation. In particular, Sn is lithiated and delithiated during the first cycle. However, as the cycle number increases, the capacity deteriorates. Ex situ TEM observations further reveal that Li–Sn alloys remain unchanged even after delithiation, and the crystallite size increases significantly. It is thus found that the capacity deterioration is attributed to the irreversible Li insertion/extraction between Sn and Li–Sn alloys.

Electric field and EHD flow in longitudinal wire-to-plate DC and DBD electrostatic precipitators: A numerical study

In this study, the electrical and electrohydrodynamic (EHD) flow properties of a wire-to-plate electrostatic precipitator with a longitudinal wire electrode are investigated through a numerical simulation. The two modes of operation are considered: DC and AC supply voltages. The AC model features dielectric layers over collecting electrodes, hence a dielectric barrier discharge mechanism. To predict the ion concentration on the wire electrode surface, Kaptzov's hypothesis is employed. Both electrical and fluid flow equations are solved using the Finite Element Method. The EHD flow properties are estimated by simulating electric field, space charge density and fluid flow in the 3D precipitator channel. The results suggest that 1000 Hz frequency in AC supply generates EHD force with a 9 × 104 N/m3 maximum alue, which is an order of magnitude higher than the same value under DC supply. However, for 100 Hz supply voltage frequency the EHD force is lower than that for the DC supply and equal to 8 × 103 N/m3, although with a greater level of vorticity. The proposed models for DC and AC supply voltages display close characteristics to their experimental references with an average relative error of 13.5%.

Research Progress on Audible Noise Emitted from HVDC Transmission Lines

The audible noise (AN) of DC transmission lines is a crucial factor affecting environmental assessment and electromagnetic design. In recent years, the public has paid increasing attention to the audible noise after the emergence of the HVDC technique. This paper emphatically reviewed the work investigating audible noise characteristics in both time and frequency domains, especially the correlation between sound and discharge. The proposed mechanisms of DC audible noise and the mitigating techniques are summarized, including the noise generation process, the physical models, the measurement method, and the mitigating technologies. It is found that the existing literature mainly focused on the prediction and characteristics of AN, the environmental factors which influence AN, and the methods to minimize AN emission. However, existing achievements still need to be improved to fully understand the mechanism of AN generation and solve the adaptability problem of AN prediction methods. The following aspects are valuable in future research: The correlation between audible noise and other corona effects will help solve the problem of difficulty in measuring audible noise in field condition; The corona discharge mechanism and weather resistance anti-corona coating when raindrops are attached to the surface of the transmission line, which will help guide the development and application of anti-corona coatings for the transmission line. Future research should also understand the mechanism of sound wave generation when considering the space charge effect.

Piezo/sono-catalytic activity of ZnO micro/nanoparticles for ROS generation as function of ultrasound frequencies and dissolved gases

We report an accurate study on sonocatalytic properties of different ZnO micro and nanoparticles to enhance OH radical production activated by cavitation. In order to investigate some of the still unsolved aspects related to the piezocatalytic effect, the degradation of Methylene Blue and quantification of radicals production have been evaluated as function of different ultrasonic frequencies (20 kHz and 858 kHz) and dissolved gases (Ar, N2 and air). The results shown that at low frequency the catalytic effect of ZnO particles is well evident and influenced by particle dimension while at high frequency a reduction of the degradation efficiency have been observed using larger particles. An increase of radical production have been observed for all ZnO particles tested while the different saturating gases have poor influence. In both ultrasonic set-up the ZnO nanoparticles resulted the most efficient on MB degradation revealing that the enhanced radical production may arise more from bubbles collapse on particles surface than the discharge mechanism activate by mechanical stress on piezoelectric particles. An interpretation of these effects and a possible mechanism which rules the sonocatalytic activity of ZnO will be proposed and discussed.

Experimental and numerical investigation of surface streamers in a nanosecond pulsed packed bed reactor

Packed bed reactor (PBR) is the commonly used configuration in plasma catalysis, and its plasma characteristics have been extensively investigated. The filled catalysts in PBR make it challenging to carry out in-situ measurements of electric fields, and limited experimental data have been obtained. We investigated the surface streamer propagation and electric field distribution in a simplified PBR through simulations and experiments. The simplified PBR in the experiments is comprised of a blade-plate electrode structure filled with an Al2O3 column (ϵr = 9) in the discharge gap. An ICCD camera and an electric field diagnosis method called EFISH (electric field induced second harmonic generation) were employed, and a two-dimensional fluid model was established for the simulation. Four discharge types in the PBR were identified based on ICCD images and simulation results, including polar discharge at the contact areas, surface streamer along the dielectric column, expansion of surface discharge along the dielectric column, and surface ionization waves along the dielectric plate. Surface streamers with opposite propagation directions were found in the model, namely the forward streamer during the pulse rising time and the reverse streamer during the pulse falling time. Notably, the reverse streamer exhibits a significantly lower velocity compared to the forward streamer. Both experimental measurements and simulation were conducted to investigate the spatiotemporal electric field near the surface of the packing material. The results of both E exp and E sim showed peaks with opposite polarities, and exhibited similar trends. In the simulation, the forward streamer head showed a higher electric field compared to the reverse streamer head. Moreover, during the rest pulse time, the surface electric field was more intense at the contact areas than in other regions. The findings of this work provide valuable insights into the discharge mechanism and electric field on the catalytic material surface within the PBR.

High Repetition Frequency Subnanosecond Avalanche Marx Generator

Ultrawideband electromagnetic pulses have sub-nanosecond rise time and repetition frequency above 100 kHz. Ultrawideband characteristics make it increasingly used in biomedical, intentional electromagnetic interference, and other fields. Avalanche Marx circuits are an important way to generate high-voltage sub-nanosecond pulses with high repetition rates. However, traditional avalanche Marx circuits (TAMCs) are difficult to achieve a repetition rate of 100 kHz and often fail when they reach kilohertz. The second-stage transistor is extremely vulnerable to damage, which is the principal cause of circuit failure. In this article, through the analysis of its discharge mechanism, it is found that the damage to the second-stage transistor is related to the slow on-speed of the first-stage transistor. In fact, the first-stage transistor is the last to be avalanche broken down, causing the already-opened second-stage transistor to be subjected to enormous electrical stress for an instant. This electrical stress is the passive lift voltage of the second-stage transistor, which is the direct cause of easy damage to the second-stage transistor. Therefore, an improved avalanche Marx circuit (IAMC) is proposed. By connecting a protection resistor in series with the second-stage transistor, the passive lift voltage is suppressed. In order to verify the high refrequency capability of this circuit, a 20-stage pulse generator using an IAMC is developed. It achieves a rise time of 230 ps in a 50- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $</tex-math> </inline-formula> load, an amplitude of 1.65 kV, and a repetition rate of 100 kHz. After adding the necessary cooling device, it finally achieves a stable output of 230-ps rise time, 730-V amplitude, and 700-kHz repetition rate on a 50- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $</tex-math> </inline-formula> load.