Electrode Voltage Research Articles

Optimization of dissolved hydrogen concentration for mitigating corrosive conditions of pressurized water reactor primary coolant under irradiation (1) evaluation of water radiolysis

ABSTRACT A major subject for evaluating the corrosive conditions in the pressurized water reactor (PWR) primary coolant is to determine the optimal hydrogen concentration for mitigating primary water stress corrosion cracking (PWSCC) without adverse effects on major structural materials. An analytical method combining water radiolysis and electrochemical corrosion potential (ECP) analyses was proposed for evaluating the corrosive conditions in PWR primary coolant. These procedures originally developed for boiling water reactors (BWRs) were successfully extended to PWRs with different water chemistry parameters, including pH, temperature, and radiation qualities, after minor changes in the original procedures and major input parameters, such as the inclusion of the effects of alpha radiolysis and Li+ (Na+) and H+ effects for the anodic polarization curve. This study discusses the results of water radiolysis analysis for PWR primary coolant, and the characteristic behavior of hydrogen peroxide (H2O2) as a function of hydrogen inlet concentrations in PWR primary coolant conditions (higher pH and α-ray irradiation). A possible reaction scheme involving eaq – was proposed for H2O2 suppression under alkaline conditions. The corrosive conditions were discussed in the following publication, using ECP as the major index for PWR corrosive conditions.

Scaling Down the Great Egypt Pyramids to Enhance CO2 Splitting in a Micro DBD Reactor

The CO2 splitting reaction has been investigated in a plate-to-plate micro DBD reactor with a high voltage electrode having pyramid charge injection points. The presence of sharp points (pyramids) creates zones with enhanced electric field around them. The minimum discharge voltage in the pyramid micro DBD reactor reduced from 6.5 to 5.2 kV (peak-to-peak). At the same time, the CO2 conversion increased 1.5 times as compared to that in the reactor with a flat electrode. Lowering the discharge gap from 0.50 to 0.25 mm resulted in more intense microdischarges, further increasing CO2 conversion by 1.3 times. At the same time, the energy efficiency increased further by 1.3 times. There exists an optimum residence time of 0.5 ms as a result of an interplay between plasma contact time and flow non-uniformity. The highest energy efficiency of 20% was obtained at a 3 W power, achieving a CO2 conversion of 16%.

Series resonance effects of a variable inductor termination on the nonpowered electrode in capacitively coupled plasmas

The effect of LC series resonance on the voltage of a nonpowered electrode in a capacitively coupled plasma is investigated by connecting a variable inductor to the nonpowered electrode. Two distinct LC series resonances are observed while varying the reactance of the variable inductor. The first resonance occurs between an inductor and a vacuum variable capacitor, thereby resulting in the voltage of the nonpowered electrode approaching zero. The reactance between the inductor and the vacuum variable capacitor is minimized at this resonance, thereby enabling the nonpowered electrode voltage to remain close to 0 V even with increased applied RF power. The second resonance is a series resonance between the variable inductor and the nonpowered electrode sheath, leading to a maximization of the nonpowered electrode voltage. The reactance between the variable inductor and the nonpowered electrode sheath is minimized at this resonance. As the applied RF power increases under the second resonance condition, the voltage of the nonpowered electrode increases, thereby resulting in a significant increase in the maximum electron density by approximately 35%. This increase in the electron density at the second resonance can be attributed to enhanced stochastic heating due to the sharp increase in the sheath voltage.

Effect of variable cross-section electrode on the battery performance of all-vanadium redox flow battery

The global warming can be relieved by the application of the renewable energy, which should be supported by the large-scale energy storage such as the vanadium redox flow battery (VRFB). The charge-discharge reactions mainly take place in the porous electrodes, which can influence the battery performance. In the paper, a variable cross-section electrode with interdigital flow field was proposed to enhance the mass transfer in the porous electrode. The charge-discharge voltage, overpotential, concentration distribution and uniformity factors are predicted by a 3-D numerical model to evaluate the battery performance of different electrodes (the Conventional electrode; Variable coss-section electrode #1: the variable coss-section electrode with the interdigital flow field distributed on one side; Variable coss-section electrode #2: the variable coss-section electrode with the interdigital flow field distributed on both sides). The discharging voltage of the variable coss-section electrode #2 was 1.25% higher than that of the variable coss-section electrode #1. The uniformity factor of the variable coss-section electrode #1 and the variable coss-section electrode #2 was 14.24% and 19.56% higher than that of the conventional electrode, respectively. Considering the machining process and promotion of the battery performance, the variable coss-section electrode#1 was the best design of the three battery models mentioned in this article.

Understanding the effect of SiC/epoxy coating on surface flashover under DC voltage: from surface charge accumulation

Charge accumulation at the insulator surface significantly alters the electric field distribution under DC voltage and can lead to unpredictable flashover. It is realized that the surface flashover voltage is reliant on the charge distribution approaching flashover occurrence (CDAFO). A method of how to judge the moment approaching flashover was proposed in this study to clarify how surface charges induced flashover, whereby the dynamic distributions of surface charges, including the CDAFO, were obtained from the instant of voltage application to the moment approaching flashover. The resulting flashover was analyzed with regards to insulators coated in SiC/epoxy, including an examination of the dominant charging pathway during voltage rising and a discussion of the relationship between the CDAFO and flashover voltage. Despite voltage polarities and SiC content, a reversal of charge polarity from hetero-polar to homo-polar was observed during voltage rising. Furthermore, it was discovered that the CDAFO was homo-charge accumulation, and an increase in SiC content resulted in greater homo-charges. A theory outlining homo-charge’s enhancement of flashover voltage by weakening the electric field near the high voltage electrode was also proposed. Consequently, because of the improved effect of homo-charges on flashover voltage, the addition of SiC led to the boost of flashover voltage.

Surface charge accumulation of post insulator: Dominant charge transition under different conditions

AbstractAn insulator surface charge may be responsible for flashover along the insulator surface. In this study, experimental investigations of post insulator surface charge are performed using a variety of voltage, gas type, and gas pressure conditions. Combining the model of surface charge transport, the dominant charge transition is revealed considering gas partial discharge. The results show that hetero‐polar charge accumulates near the high voltage electrodes on the insulator at one atmospheric pressure with an applied DC voltage ranging from −10 to −60 kV. The area ratio of the hetero‐polar charge increases from 23% to 53%. It also generates a reversed polarity of surface charges. Under −20 kV, the surface charge near the grounded electrode gradually becomes homo‐polar charges with the decrease of SF6 in 0.5 MPa SF6/N2 gas mixtures. In this case, the most dominant pathway for charge accumulation is through the insulation gas rather than the insulator. For the 20%SF6/80%N2 gas mixtures, homo‐polar charge speckles appear near the grounded plate electrode when the pressure of SF6/N2 gas mixtures decreases to 0.1 MPa. This means that the partial discharge occurs in gas side under a lower gas pressure. Refer to the presenting findings, the dominant charge transition on post insulators is provided as an important reference.

Impact of Flexible Circuit Bonding and System Integration on Energy Resolution of Cross-Strip CZT Detectors.

Cadmium zinc telluride (CZT) detectors enable high spatial resolution and high detection efficiency and are utilized for many gamma-ray and X-ray spectroscopy applications. In this article, we describe a stable bonding process and report on the characterization of cross-strip CZT detectors before and after bonding to flexible circuit. The bonding process utilizes gold stud bonding and polymer epoxy technique to bond the flexible circuits to two CZT crystals and form a detector module in an anode-cathode-cathode-anode (ACCA) configuration. The readout electronics is optimized in terms of shaper setting and steering electrode voltage. The average full-width half maximum (FWHM) energy resolution at 662 keV of 110 CZT crystals tested individually was 3.5% ± 0.59% and 4.75% ± 0.48% prebonded and post-bonded, respectively. No depth correction was performed in this study. The average FWHM energy resolution at 662 keV of the scaled-up system with 80 CZT crystals was 4.40% ± 0.53%, indicating the scaled-up readout electronics and stacking of the modules does not deteriorate performance. The proper shielding and grounding of the scaled-up system slightly improved the system-wide performance. The FWHM energy resolution at 511 keV of the scaled-up system was 5.85% ± 0.73%.

Forced convection heat transfer characteristics of aviation kerosene in a horizontal tube under electric field

The electrohydrodynamic (EHD) technique can considerably improve the performance of aviation heat exchangers. In this study, the forced convection heat transfer characteristics of aviation kerosene in a horizontal wire-tube structure under electric field were investigated. The influences of positive and negative high voltages on the heat transfer in test section were compared. Key factors affecting EHD heat transfer enhancement, such as fuel inlet temperature, mass flow, heat flux and operating pressure were explored. Furthermore, the cause of electrode corrosion was investigated using Scanning Electron Microscope (SEM) and Energy Disperse Spectroscopy (EDS). The experimental results showed that the circumferential temperature distribution of the test section was uneven owing to buoyancy in the absence of electric field. As the applied voltage increased, temperature heterogeneity decreased. Negative voltage improved the heat transfer more effectively than positive voltage. The electric field enhanced the heat transfer of high-temperature fuel more effectively. In the charge injection mechanism voltage range, the numerical simulation results were more similar to the negative voltage experimental results. The heat transfer enhancement ratio was reduced by an increase in the fuel mass flow and operating pressure. A higher heat flux led to a more substantial buoyancy effect, which inhibited the electric field force effect. Finally, the corrosion rate of positive high voltage electrode was the highest, resulting in rapid loss of metal elements from the electrode surface.

Key Modes of Ignition and Maintenance of Corona Discharge in Air

Theoretical and experimental studies of various modes of corona discharge operation in atmospheric pressure air are presented in this short review. The original results of modeling negative corona discharges are presented, taking into account the non-stationary plasma-chemical kinetics of charged particles in air plasma. The space–time evolution of the discharge in needle-to-plane geometry is investigated and analyzed. Several stages of discharge development are revealed from the moment of initiation of a low-negative current corona to the quasi-stationary mode of a glow discharge. Experimental data of the authors are presented. Modern technology and diagnostic equipment with a wide variation of the main parameters (the shape and polarity of the applied voltage, the type of gap, etc.) was used. The measurement of the optical characteristics of the plasma glow was carried out with high spatial resolution. Corona discharge current pulse profiles in the air at atmospheric pressure have been recorded with subnanosecond time resolution. With a positive polarity of the pin electrode and high voltage, a transition from a spherical streamer initiating a corona discharge to a cylindrical streamer is shown. The author’s results are rigorously evaluated through a critical comparison with findings from other research groups.

Numerical simulation of the enhancing effect of micro–nano protrusions on electrostatic fog harvesting

Fog harvesting is one potential approach to provide supplementary water resources in arid areas. Considerable research has been devoted to electrostatic fog harvesting technology, but there are still some problems, such as high voltage, complex structures and expensive cost. Decorating micro–nano protrusions on the electrode is an effective method to lower the operating voltage and improve fog harvesting efficiency, and the enhancement effect of protrusions has already been experimentally demonstrated. However, the enhancement mechanism at the microscopic level is less reported. This manuscript tries to explain why micro–nano protrusions can enhance the discharge and electrostatic fog harvesting, via numerical simulation. Three key processes of corona discharge, fog droplet migration and fog harvesting efficiency are discussed in detail, especially the influence of droplet size, the tip radius of the protrusion, the protrusion–protrusion angle and so on. The numerical simulation results show that the inception voltage of the barbed electrode decreases from 7 kV to 3 kV (a decrease of 57%), and the current increases significantly (e.g. by 68% at 15 kV). At 15 kV, the fog harvesting efficiency of the barbed electrode is higher (29.8%) than that of the smooth wire (25.7%), even with a less-effective collection area. The collection efficiency increases with the droplet size, and there is an optimized ratio (∼1‰) of the protrusion tip radius and wire radius to gain high collection efficiency. These research results are beneficial for understanding the microscopic mechanism of protrusions that enhance electrostatic fog harvesting, and provide guidance for further fog harvesting equipment improvement.

Processing of Al/SiC/Gr Hybrid Composite on EDM by Different Electrode Materials Using RSM-COPRAS Approach

The present research used the stir-casting method to develop an Al-based composite. The developed composite exhibited challenges while being processed on conventional machining. Thus, a non-traditional machining process was opted to process the composite. The machining variables selected for the current research were the pulse off time (Toff), pulse on time (Ton), servo voltage (SV), current (I), and tool electrode. Three tool electrodes (SS-304, copper, and brass) were used to process the developed composite (Al/SiC/Gr). The experimental plan was designed using response surface methodology (RSM). The output responses recorded for the analysis were the material removal rate (MRR) and tool wear rate (TWR). The obtained data was optimized using complex proportional assessment (COPRAS) and machine learning methods. The optimized settings predicted by the RSM–COPRAS method were Ton: 60 µs; Toff: 60 µs; SV: 7 V; I: 12 A; and tool: brass. The maximum MRR and TWR at the suggested settings were 1.11 g/s and 0.0114 g/s, respectively. A morphological investigation of the machined surface and tool surface was conducted with scanning electron microscopy. The morphological examination of the surface (machined) presented the presence of cracks, lumps, etc.

ZnO doped SnO2 nano flower decorated on graphene oxide/polypyrrole nanotubes for symmetric supercapacitor applications

Due to their high power density, lengthy cyclability, quick charge-discharge rates, and environmentally friendly design, supercapacitors are incredibly effective electrochemical energy storage devices. A lot of work has been progressed in this direction to increase the specific power and cyclic stability of supercapacitor mainly by using various metal oxides with 2D composites and high concentration electrolytes. But, there are some challenging issues like low energy density, high production cost, and short cyclic life. In this work, we aimed to resolve the low energy density and operating voltage of electrodes by selecting multiphase inorganic-organic material with a suitable concentration of electrolyte. To create such supercapacitor electrodes for high energy storage applications, ZnO doped SnO2 nanoflower decorated on graphene oxide/polypyrrole nanocomposite, which are novel materials with large specific surface area and cyclic stability were studied.The electrochemical study of the nanocomposite materials is done by studying the cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance (EIS) techniques. The supercapacitor device fabrication is processed using ZS/GP2 electrode, and the analysis of supercapacitor performance is also studied. As a result, ZS/GP2 nanocomposite showed a good capacitive behavior with a maximum specific capacitance of 392 F g−1 at 75 mV s−1 scan rate with significantly high specific energy and power density of 31.6 Wh kg−1 and 5177 W kg−1, respectively after the 27,000 consecutive charge-discharge (GCD) cycles at the current density of 0.25 A g−1. The results evidence that these hybrid materials are highly promising electrode materials for energy storage applications.

Online evaluation of resistance spot welding quality and defect classification

Resistance spot welding (RSW) is widely used in industrial product manufacturing, and weld quality is critical to ensure the safety and reliability of mechanical structures. With product quality improvement, the online monitoring of weld quality has become an urgent issue. Therefore, a method for online evaluation of RSW quality and automatic classification of welding defects based on mild steel is proposed. By acquiring the welding current and electrode voltage signals of the welding process in real time, a finite impulse response low-pass filter based on the Blackman window function is designed to perform zero-phase filtering of the dynamic resistance (DR). The influence of three welding parameters on the nugget diameter and shear strength of spot welding of DC01 mild steel was studied through the control variable method to determine the optimum welding parameters. Since the main defects of the RSW process are classified as expulsion defects and incomplete fusion defects, minor adjustments were made to the welding parameters to produce expulsion and incomplete fusion defects. Features in the time domain are extracted from the DR curves signals of normal, expulsion, and incomplete fusion welding spots, and the performance of the extracted features in the classifier is analyzed. Improvements are made to classify normal and expulsion spots with low accuracy, a new method is proposed that can accurately classify the quality of the welding spots. Through online evaluation tests of quality on 200 welding spots, the online evaluation test showed results that closely matched the validation test results. The results of the classification performance tests show that this study can be used for online evaluation of RSW quality and automatic classification of the welding spot defects of the DC01.

Controlling the charge of dust particles in a plasma afterglow by timed switching of an electrode voltage

A method is demonstrated for controlling the charge of a dust particle in a plasma afterglow, allowing a wider range of outcomes than an earlier method. As in the earlier method, the dust particles are located near an electrode that has a DC voltage during the afterglow. Here, that DC voltage is switched to a positive value at a specified delay time, instead of maintaining a constant negative voltage as in the earlier method. Adjusting the timing of this switching allows one to control the residual charge gradually over a wide range that includes both negative and positive values of charge. For comparison, only positive residual charges were attained in the earlier method. We were able to adjust the residual charge from about −2000 e to +10 000 e, for our experimental parameters (8.35 µm particles, 8 mTorr argon pressure, and a DC voltage that was switched from −150 V to +125 V within the first two milliseconds of the afterglow). The plasma conditions near the dust particles changed from ion-rich to electron-rich, when the electrode was switched from cathodic to anodic. Making this change at a specified time, as the electrons and ions decay in the afterglow, provides this control capability. These results also give insight into the time development of a dust particle’s charge in the afterglow, on a sub-millisecond time scale.

Transduction of quantum information from charge qubit to nanomechanical cat-state

We suggest a nanoelectromechanical setup and corresponding time-protocol of its manipulation by which we transduce quantum information from charge qubit to nanomechanical cat-state. The setup is based on the AC Josephson effect between bulk superconductors and mechanically vibrating mesoscopic superconducting island in the regime of the Cooper pair box. Starting with a pure state with quantum information initially encoded into superposition of the Cooper pair box states, applying a specially tailored time-protocol upon bias voltage and gate electrodes, we obtain a new pure state with information finally encoded into superposition of nanomechanical coherent states constituting the cat-state. This performance is achieved using quantum entanglement between electrical and mechanical states. Nanomechanical cat-states serve as a “storage” of quantum information, motivated by significantly longer decoherence time with respect to the charge qubit states, from which the information can be transdued back to the charge qubit applying the reverse time-protocol.

How living cells are affected during the cold atmospheric pressure plasma treatment

When the electric discharge process is limited by high voltage electrodes shielding, the ionization measure would be controlled to less than one percent and the temperature to less than 37 °C even at atmospheric pressure, so-called cold atmospheric pressure plasma (CAP). CAP has been found to have profound medical applications in association with its reactive oxygen and nitrogen species (ROS/RNS). In this way that during plasma exposure, the subjected medium (e.g. cell cytoplasmic membrane in plasma therapy) interacts with ROS/RNS. Accordingly, a precise study of the mentioned interactions and their consequences on the cells' behavior changes, is necessary. The results lead to the reduction of possible risks and provide the opportunity of optimizing the efficacy of CAP before the development of CAP applications in the field of plasma medicine. In this report molecular dynamic (MD) simulation is used to investigate the mentioned interactions and a proper and compatible comparison with the experimental results is presented. Based on this, the effects of H2O2, NO and O2 on the living cell's membrane are investigated in biological conditions. Our results show that: i) The hydration of phospholipid polar heads would be enhanced associated with the H2O2 presence. ii) A new definition of the surface area assigned to each phospholipid (APL), more reliable and compatible with the physical expectations, is introduced. iii) The long-term behavior of NO and O2 is their penetration into the lipid bilayer and sometimes passing through the membrane into the cell. The latter would be an indication of internal cells' pathways activation leading to modification of cells' function.

A sigma-delta interface built-in self-test and calibration for microelectromechanical system accelerometer's utilizing interpolation method

This work presents the capacitive micromechanical accelerometer with a completely differential high-order switched capacitor sigma-delta modulator interface. Such modulation interface circuit generates one-bit output data using a third sigma-delta modulator low-noise front-end, doing away with the requirement for a second enhanced converter of resolution to encode the feedback route analog signal. A capacitive micromechanical sensor unit with just a greater quality factor has been specifically employed to give greater resolution. The closed-loop and electrical correction control are used to dampen the high-Q values to get the system's stability with high-order. This microelectromechanical system (MEMS) capacitive accelerometer was calibrated using a lookup table and Akima interpolation to find manufacturing flaws by recalculating voltage levels for the test electrodes. To determine the proper electrode voltages for fault compensation, COMSOL software simulates a number of defects upon that spring as well as the fingers of the sensor system. When it comes time for the feedback phase of a proof mass displacement correction, these values are subsequently placed in the lookup table.

Multi-perspective observation of streamer discharge morphology

As the initial discharge, streamer is the key to explore the long air gap discharge. At present, the experimental research on streamer discharge focus on observation from a single perspective. In order to understand streamer discharge more accurately, it is necessary to conduct photographic observation from multiple perspectives. For this reason, the dual-camera synchronous observation experiment platform was used in this paper to observe the positive streamer discharge in the rod-plate gap from two perspectives under the conditions of different voltage amplitude and electrode size. The morphological characteristics of the discharge from the two perspectives were basically the same. The length and diameter of the streamer discharge increase with the increase of voltage amplitude and the decrease of the curvature of the electrode. It is found that the length and diameter of the streamer measured in the left view are basically higher than those measured in the right view, reflecting the inaccuracy of the streamer discharge observed in the two-dimensional streamer image.

Experimental study on micro electrical discharge machining of alumina–titanium carbide ceramic materials

When electric discharge machining (EDM) is used to process Al2O3-TiC ceramics, it is difficult to obtain an optimal production efficiency and tool wear rate. As the target demand of processing largely relies on the process parameters, it is pertinent to conduct an in-depth study on the process parameters. In this study, the effects of certain technological parameters on the properties of EDM Al2O3-TiC ceramic materials were assessed and a mixed 2–3 horizontal orthogonal test method was designed. The rules of machining polarity, inter-electrode voltage, peak current, gain, pulse frequency, pulse width, inter-electrode gap and electrode length loss, electrode profile loss, material removal rate were studied. The effect of process parameters on process performance was determined by range analysis. In addition, the analysis of variance revealed that machining polarity has a significant effect on the electrode loss while the electrode voltage and peak current significantly influenced the material removal rate. The optimal parameter combination was determined as negative machining polarity, 130 V inter-electrode voltage, 50 A peak current, 45 gain, 150 Hz pulse frequency, 1.0 μs pulse width, and 40 μs inter-electrode gap.

Performance prediction and parameter optimization of alumina-titanium carbide ceramic micro-EDM hole machining process based on XGBoost

Aiming at the difficulties in setting process parameters and the low accuracy of process performance prediction in electrical discharge machining (EDM) hole machining of alumina ceramics, a novel EDM process performance prediction method based on eXtreme Gradient Boosting (XGBoost) is proposed in this study. The independent variables selected include processing polarity (P), interelectrode voltage (V), peak current (I), pulse frequency (F), pulse width (T), and tool electrode and workpiece electrode gap (W), while the dependent variables are tool electrode length loss (ELW), tool electrode volume loss (EVW), and material removal rate (MRR). An L18 (21 × 35) orthogonal test is designed to obtain training samples for model development. The accuracy of the prediction results for ELW, EVW, and MRR by the XGBoost model is found to be 1.7%, 2.5%, and 9.4%, respectively. These results show a significant improvement compared to the linear regression model, with an improvement of 41.7%, 62.5%, and 19.4%, respectively. Furthermore, when compared to the support vector regression (SVR) model, the XGBoost model also shows improvement of 23.6%, 5.9%, and 12.0% for ELW, EVW, and MRR prediction accuracy, respectively. These findings suggest that the proposed XGBoost-based method is effective and accurate in predicting the performance of alumina ceramic EDM processes. In addition, the third generation nondominated sorting genetic algorithm (NSGA-III) is utilized to optimize the process parameters with both single objective and multi-objective approaches. The optimal parameters for ELW, EVW, and MRR, including the selection of machining polarity, interelectrode voltage, peak current, pulse frequency, pulse width, and tool electrode and workpiece electrode gap are obtained through the Pareto frontier of the three comprehensive optima. The average relative errors between the experimental results and the optimized results are found to be 6.46%, 10.45%, and 9.58% for ELW, EVW, and MRR, respectively, indicating the accuracy and effectiveness of the optimized results.