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A surface streamer is a ubiquitous discharge in electric equipment and surface dielectric barrier discharge. It is expected to suppress this kind of surface discharge in the insulation system, but on the other hand, the surface streamer is also utilized for the generation of active ions and the control of a gas kinetic distribution. As a product of the surface streamer, surface charge influences and characterizes the streamer's behavior. This study observed the two-dimensional transient evolution of the surface charge and the tangential electric field in a single individual surface streamer at the nanosecond level. Using a reflective Pockels effect system and a framing camera system, the surface streamer propagation under a sub-microsecond pulse voltage was measured in real time and in situ. The inception, propagation, and deceleration of a surface streamer are observed. The measurement exhibits an electrode-charge equipotential region that equivalently extends the electrode boundary. Under an anode field with a weak tangential component, the interior of the surface streamer channel exhibits local deviations from the quasi-neutrality, and a reversed tangential electric field is observed. The lateral movement of the positive charge may be responsible for this reverse electric field. The diagnostic technique presented in this study can describe the surface charge transient behavior in pulsed surface discharges, which complements the streamer model. [ABSTRACT FROM AUTHOR]

Purpose: Green building (GB) maintenance is increasingly accepted in the construction industry, so it can now be interpreted as an industry best practice for maintenance planning. However, the performance competency and design knowledge of the practice's building control instrument process can be affected by its evaluation and the information management of building information modelling (BIM)–based model checking (BMC). These maintenance-planning problems have not yet been investigated in instances such as the Grenfell Tower fire (14 June 2017, approximately 80 fatalities) in North Kensington, West London. Design/methodology/approach: This study proposes a theoretical framework for analysing the existing conceptualisation of BIM tools and techniques based on a critical review of GB maintenance environments. These are currently employed on GB maintenance ecosystems embedded in project teams that can affect BMC practices in the automation system process. In order to better understand how BMC is implemented in GB ecosystem projects, a quantitative case study is conducted in the Malaysian public works department (Jabatan Kerja Raya (JKR)). Findings: GB ecosystem projects were not as effective as planned due to safety awareness, design planning, inadequate track insulation, environmental (in) compatibility and inadequate building access management. Descriptive statistics and an ANOVA were applied to analyse the data. The study is reinforced by a process flow, which is transformed into a theoretical framework. Originality/value: Industry practitioners can use the developed framework to diagnose BMC application issues and leverage the staff competency inherent in an ecosystem to plan GB maintenance environments successfully. [ABSTRACT FROM AUTHOR]

This study examines the effects of crucial ISO 25178 parameters, including height, functional, spatial, functional (stratified), hybrid, and functional (volume), on surface wettability and the influence of key electric discharge texturing process parameters, including current and pulse ON time, on surface roughness (Sa) and water droplet contact angle. To examine the level of significance of each parameter and to determine the level of correlation, a three-level full factorial experimental design, and ANOVA analysis are used. The findings showed that over pulse ON time, the important factor influencing surface roughness (Sa) and contact angle is current. The surface roughness (Sa) is observed to vary between 4.2 and 12.7, whereas the water droplet contact angle varies between 90.7° and 120.4°. In order to find out the correlation between the surface texture parameters based on the ISO 251718, Pearson Correlation analysis were adopted and it is observed that Sa, Sq, Str, Smrk1, Sdr, Vm, and Vmp are having a substantial correlation with the contact angle. Among the ISO25178 parameters examined, Smrk1, however, has demonstrated a highest impact on the contact angle with a highest pearson correlation coefficient of −0.757. • Demonstrated the influence of important ED texturing process parameters on the surface wettability and surface roughness. • Correlated the ISO25178 surface roughness parameters with the surface wettability of electric discharge textured Ti6Al4V. • Sa, Sq, Str, Smrk1, Sdr, Vm, and Vmp are the significant texture parameters on the wettability of the ED textured surface. • Smrk1 has the maximum negative correlation with the contact angle with a correlation coefficient of -0.757. [ABSTRACT FROM AUTHOR]

The development of a surface barrier discharge driven by a negative steplike voltage pulse with an amplitude of V = –8 kV in air at the atmospheric pressure and a pulse with an amplitude of V = –15 kV in nitrogen at a pressure of 6 atm is simulated numerically. Calculations for V = –8 kV were carried out using the local-electric-field and the local-electron-energy approximations. It is demonstrated that both approximations yield similar results on the dynamics of discharge development as a whole, the cathode-layer structure, and the field distribution at the front of the discharge. Substantial differences are observed in parameters of the discharge layer adjacent to the dielectric surface, which allowed to simulate an effect similar to filamentation of the discharge in nitrogen at a pressure of 6 atm and voltage of V = –15 kV in the local-energy approximation. [ABSTRACT FROM AUTHOR]

This study explores the discharge uniformity at different cycles under different airflow velocities in nanosecond‐pulsed dielectric barrier discharge. Based on a proper choice of the airflow velocity and discharge parameters, diffuse discharges can be maintained at an air gap of 5–7 mm. At higher airflow velocities, the discharge may transition to a complex mode, in which the diffuse and filamentary regions are maintained simultaneously. When the discharge is operated at a higher frequency, higher voltage, or smaller gas gap, the area of diffuse discharge can be expanded to a certain extent. The discharge characteristics indicate that airflow lowers the gas temperature and modulates the preionization degree, which induces the generation of a diffuse discharge for a properly adjusted airflow velocity. [ABSTRACT FROM AUTHOR]

The article presents a study of the structure and properties of carbon-containing nanostructured coatings obtained by electric discharge methods. X-ray structural analysis of coatings was carried out using a DRON-4-07 diffractometer with a copper tube. Images of the surface morphology were obtained using a JSM-6700F scanning electron microscope. The coating surfaces were examined using a Solver P47H atomic force microscope. The surface hardness of the obtained samples was determined using a ball with a diameter of 1.588 mm at a load of 588.4 N. The method of electric discharge treatment of carbon-containing gases allows to obtain a nanostructured coating of almost the same size particles that form micrometer globules. Nanocarbon coating has no impurities. Particle sizes are no more 40 nm. This coating is X-ray amorphous and attenuates X-rays at wavelength λ k α = 0,154,178 nm on average by 51%. Electric discharge through a metal conductor in carbon-containing gas allows to obtain a nanostructured composite coating, which consists of carbon, metal and carbide globules and is uniform in particle size. The particle sizes obtained from tungsten wires are 40 nm, and from titanium wires—100 nm. The hardness of the substrate surface is significantly increased due to the applied coating. [ABSTRACT FROM AUTHOR]

A high-pressure direct current magnetron discharge is analyzed using a self-consistent two-dimensional fluid model. This discharge has potential interest in plasma switching applications due to its ability to generate rather dense (plasma density of ∼1019 m−3) stable nonequilibrium plasmas at pressures of ∼13.3 Pa (100 mTorr). This discharge has several advantages over nanosecond pulsed high pressure discharges used in conventional plasma switchers since it operates at much lower voltages and lower gas pressures, with the advantage of much longer cathode lifetime. In the present paper, we analyze the operating modes of this magnetron discharge for conditions close to that of Sommerer et al. [J. Phys. D: Appl. Phys. 52, 435202 (2019)]. We observe the subnormal and normal modes of the magnetron operation whose physics differs from that typical for unmagnetized plasmas. [ABSTRACT FROM AUTHOR]

Electrical breakdown in a pulsed asymmetric dielectric barrier discharge between a glass-covered mesh electrode and a grounded metal electrode in the air at atmospheric pressure is investigated. Volume discharge forms between the metal tip and the dielectric surface and spreads over the dielectric surface. Breakdown and discharge behaviors depend on the polarity of the charged electrode covered with glass compared to the metal rod electrode. In the case of the dielectric cathode (covered mesh), volume discharge features a stronger and longer-lasting emission. Volume discharge is weaker with outstretched surface discharge developing on the opposite glass electrode sustained by the embedded mesh when the metal rod functions as a cathode. The development and spatial distribution of the surface discharge depend on the relative polarity of the dielectrics caused by the charge deposition of the preceding discharge and is independent of the polarity of the applied high voltage. The discharge emission is brighter for the metal cathode and dielectric anode than for the metal anode, with a branching discharge developing and spreading in a star-like structure along the embedded grid, while a ring-like structure was observed for the metal anode and dielectric cathode. The duty cycle influences the discharge development and properties through the effects of the gas phase and surface pre-ionization. [ABSTRACT FROM AUTHOR]

Electrical discharge in liquids is a research field that has great potential in environmental and technological applications. Depending on the experimental conditions (liquid nature, interelectrodes distance, applied voltage, pulse width, etc.), various discharge modes can be obtained. The involved physical processes have relatively fast spatiotemporal dynamics and, therefore, are not well understood. In this study, we report the electrical characterization, coupled with time-resolved light detection (using a photomultiplier, PM, tube), of positive and negative pulsed nanosecond spark discharges in de-ionized water using copper electrodes (distanced by ∼50 μm) in a pin-to-plate configuration. A detailed analysis of the current–voltage waveforms during the pre-breakdown and the breakdown phases is shown, and we found that the pre-breakdown phase depends on the high voltage magnitude only for positive polarity. On the other hand, the PM signals showed dependence on the voltage magnitude and on the pulse width, and various emission phases are observed. These phases can be related to the discharge power and/or to the discharge current. Filtered PM signals at various wavelengths are also acquired, and their temporal dynamics are discussed regarding the discharge conditions. [ABSTRACT FROM AUTHOR]

Stray current is a relevant phenomenon in particular for DC electrified transportation systems, affecting track and infrastructure within the right of way and other structures and installations nearby. It worsens with time and the level of protection depends on timely maintenance, as well as correct design choices. The assessment of track insulation is the starting point for both stray current monitoring systems and at commissioning or upon major changes. Standardized methods (ref. EN 50122-2 or IEC 62128-2) have been almost unchanged in the last 20 years but suffer from accuracy issues and variability due to parameters and conditions not under the operator's control. The uncertainty of test methods is increasingly important now that contractual specifications require a high level of insulation for new systems. A critical discussion and analysis of the sources of variability and practical constraints is proposed, followed by an evaluation of uncertainty, with the objective not only to assess the accuracy of the provided results, but also to foster research on innovative, more flexible and accurate methods. [ABSTRACT FROM AUTHOR]

The generation of high-density plasmas on the surface of porous catalysts is very important for plasma catalysis, as it determines the active surface of the catalyst that is available for the reaction. In this work, we investigate the mechanism of surface and volume plasma streamer formation and propagation near micro-sized pores in dielectric barrier discharges operating in air at atmospheric pressure. A two-dimensional particle-in-cell/Monte Carlo collision model is used to model the individual kinetic behavior of plasma species. Our calculations indicate that the surface discharge is enhanced on the surface of the catalyst pores compared with the microdischarge inside the catalyst pores. The reason is that the surface ionization wave induces surface charging along the catalyst pore sidewalls, leading to a strong electric field along the pore sidewalls, which in turn further enhances the surface discharge. Therefore, highly concentrated reactive species occur on the surfaces of the catalyst pores, indicating high-density plasmas on the surface of porous catalysts. Indeed, the maximum electron impact excitation and ionization rates occur on the pore surface, indicating the more pronounced production of excited state and electron-ion pairs on the pore surface than inside the pore, which may profoundly affect the plasma catalytic process. [ABSTRACT FROM AUTHOR]

Copyright of Railway Standard Design is the property of Railway Standard Design 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.)

An experimental setup was created based on a model combustion chamber with a system for generating plasma exposure in the form of a surface electric discharge. This setup makes it possible to study the effect of plasma exposure on the combustion of gaseous methane in a high-enthalpy quasi-air flow in a cylindrical channel with the following inlet parameters: Mach number М = 2.8–3 and stagnation temperature T* = 1700–2500 K. The results of numerical simulation of the features of the flow structure in a model combustion chamber without combustion and during the combustion of gaseous methane are presented. The experimental data were obtained on an increase in the coefficient of completeness of methane combustion in a supersonic quasi-air flow after plasma exposure by varying the excess air coefficient in the range α = 1.2–2.3. The distributions of static pressure along the gasdynamic path and the values of the flow momentum in the outlet section of the model combustion chamber, which are realized under plasma exposure on the reacting flow, are obtained, which indicate the implementation of an effective working process. [ABSTRACT FROM AUTHOR]

The current work aims to study the influence of discharge energy and debris accumulation on wire break failure and surface integrity aspects like surface roughness, subsurface hardness, and geometrical errors during the wire EDM of Inconel 718. The responses considered for analysing the geometrical accuracies are flatness error, roundness error and cylindricity error. Four different wire electrodes were considered for the study based on the wire strength and coatings, namely hard zinc coated brass, half-hard zinc coated brass, hard uncoated brass, and half-hard uncoated brass wire electrodes. The geometric accuracy of the machined parts is closely related to the choice of wire electrode. High-tensile strength hard wires were observed to machine the surfaces with maximum accuracy. Also, the zinc coated wires were observed to cut faster compared to the uncoated wire electrodes. The study revealed that there exists a strong influence of discharge energy on the surface integrity of wire electric discharge machined surface. The zinc and copper elemental contamination was minimal for uncoated wire electrodes at lowest discharge energy mode. Wire wear phenomena was analysed for both coated and uncoated wires. Discharge energy had a significant impact on the electrode wear of coated and uncoated wire electrode. [ABSTRACT FROM AUTHOR]

This research evaluates the use of novel 3D-printed titanium alloy electrodes (3DPEs) as electrical discharge coating (EDC) on tungsten surfaces. Characterization through experimental analyses revealed that 3DPEs provide significant improvements in coating thickness and titanium content when compared to conventional EDC techniques. At suitable parameters, the 3DPE coatings achieved a thickness of 119.61 μm, surpassing conventional coatings at 15.18 μm. Additionally, the 3DPE coatings exhibited higher titanium concentrations, reaching 74.93%, indicating enhanced performance. A statistical analysis highlights the balance between surface roughness and material transfer rate (MTR), with conventional coatings exhibiting a more favorable balance. Optimal pulse on/off times maximize MTR and minimize surface roughness, respectively, with 3DPE coatings offering a more straightforward optimization path. Therefore, 3DPEs present a transformative approach to EDC, offering thicker, more uniform coatings with customizable electrical properties for diverse applications. • Incorporating 3D-printed electrodes (3DPE) for Electric Discharge Coating (EDC). • 3D-printed Ti alloy electrodes in EDC enhance coating thickness and increase Titanium content on tungsten surfaces. • 3DPE coatings achieved 119.61 μm thickness, surpassing conventional coatings by a considerable margin. • Optimal pulse on/off times of 1000 μs and 400 μs maximize MTR and minimize surface roughness, respectively. • Statistical analysis reveals a balance between surface roughness and MTR, favouring conventional coatings over 3DPEs. [ABSTRACT FROM AUTHOR]

The surface roughness of deposited conducting thin films is responsible for various materials reliability problems in nanoelectronics and nanofabrication technologies. Here, we report a modeling and simulation study that aims at optimizing the electrical surface treatment of deposited conducting thin films as a physical processing strategy for their surface roughness reduction. Our study is based on a continuum model of film surface morphological evolution that accounts for the residual stress in the deposited conducting thin film, the film's wetting of the substrate layer that it is deposited on, film texture and surface diffusional anisotropy, and surface electromigration. Through systematic linear stability analysis and dynamical simulation protocols, we examine in detail the effects of film surface crystallographic orientation and applied electric field direction toward minimizing the electric field strength required for film surface smoothening. We find that the critical electric field strength requirement for surface roughness reduction on {110}, {100}, and {111} surfaces of face-centered cubic crystalline conducting thin films exhibits a very strong dependence on the applied electric field direction, expressed as the electric field misalignment with respect to the principal residual stress directions in the film and the fast surface diffusion directions. Based on these findings, we optimize the electrical treatment strategy for surface roughness reduction of conducting thin films with respect to all relevant processing and material parameters. [ABSTRACT FROM AUTHOR]

It is shown that the NSDD (non-soluble deposit density) of insulators with different structures can be predicted using the insulators' structure coefficient and the reference XP-160 insulator's NSDD. In [[42]], Nan et al. investigated the pollution flashover characteristics of four types of AC composite crossarm insulators with diameters ranging from 100 mm to 450 mm under different voltage grades (from 66 to 1000 kV). Haque et al. [[49]] proposed a comprehensive survey including 144 citations, focusing on the application and suitability of polymeric materials as insulators in power equipment such as cables, transformers, insulators, etc. The results involving the effects of the surface hydrophobicity state of silicone rubber, core diameter, umbrella structure, arrangement, and insulation distance on the pollution flashover voltage of the composite crossarm insulators can be helpful for the structural design and optimization of the composite crossarm insulators. [Extracted from the article]

This article presents the results of an experiment designed to study creeping discharges on a solid insulating surface immersed in palm kernel oil methyl ester (PKOME) compared with those produced from mineral oil (MO). The investigation takes place under standard negative lightning impulse voltage application, and for the three following solid insulating surfaces: hardened glass (HG), porcelain (PO), and simple glass (SG). The distributions of the radial discharge occupancy densities as a function of the thickness of the solid material and the insulating liquid are evaluated. A statistical study of the total and final length of the branches produced by the discharges is presented, as well as the current amplitudes and the charge produced by this phenomenon. A fractal analysis of the phenomenon is also presented. The experimental results show that the distribution of the average radial density of the discharge, the total and final lengths of the branches, and fractal dimension depend strongly on the physicochemical characteristics of the insulation system. [ABSTRACT FROM AUTHOR]

Local pH changes were produced upon electrochemical reactions. Cyclic application of reductive and oxidative potentials resulted in the formation of pH waves in the form of distinct solution layers. Multiple layers with basic and acidic pH values were visualized with a fluorescence confocal microscope following fluorescence of pH-dependent dyes. [ABSTRACT FROM AUTHOR]

Copyright of Railway Signalling & Communication Engineering is the property of Railway Signalling & Communication Engineering 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, we present an experimental and theoretical study of a cylindrical atmospheric pressure dielectric barrier discharge (DBD) operating in the filamentary mode. An analytical model that takes into account the nonuniformity of the charge distributions on the dielectrics was developed. Using the model, it is possible to estimate important characteristics of a DBD device, like breakdown voltage, mean power consumption, and circuital parameters, directly from the geometry and physical characteristics of the device. The model also helps to understand and quantify some aspects of the behavior of the DBD discharge, like the decrease of breakdown voltage as the amplitude of the applied voltage increases, and how the fraction of area of dielectric covered with deposited charge determines the device performance. The theory was tested with experiments performed with a DBD operated in atmospheric air, with voltages from 14 to 22 kV peak to peak, and a frequency of 10 kHz. [ABSTRACT FROM AUTHOR]

Using the measurement data in a wind–sand flux on the desertified areas of Astrakhan oblast and Kalmykia, it has been established that the time variability of saltating and dust aerosol particle concentrations, the electric characteristics of the wind–sand flux, including electric currents of saltation, the volume charge of dust aerosol particles, and the electric field intensity in the near-surface layer of the atmosphere within a range of ~30 s to 30 min are determined by the low-frequency variations in the horizontal component of the wind velocity. According to the data of measurements, over the desertified area, the electric charge surface density reaches +25 nC/m2. The empirical probability distribution of a specific charge for sand grains under the condition of quasi-continuous saltation is obtained. A saltation initiation mechanism by electric discharges on the underlayer surface is proposed. An analytical model of particle liftoff to the near-surface layer of the atmosphere by electric discharges on the underlayer surface is presented. It is shown that, during the electric (corona) discharge, the saltating particle launch velocity can exceed 1 m/s. [ABSTRACT FROM AUTHOR]

The interface of multi-layer insulation is a relatively weak point in the cable system during the long-term high-temperature service. Space charge is prone to continuously accumulate in the interface area, leading to the deterioration of electrical properties and even insulation failure in advance. The knowledge about thermal oxidation of polyethylene (PE) materials at the molecular level is still urgent to explore. Herein, single-layer and double-layer PE insulation, representing the typical insulation structure of frequency-shift pulse voltage track cables, were prepared and thermally aged in the oven for up to 360 h. Thermal, mechanical, electrical, and space charge characterizations were systematically carried out. Thermogravimetric analyzer and oxidation induced temperature (OIT) measurements confirmed that LDPE's thermal-oxidative aging temperature range was the lowest among the three PE groups in the O2 atmosphere. After 360 h thermal aging, the tensile property of HDPE material kept relatively stable, while the elongation at break of the other two groups was lower than 50%. Unaged HDPE exhibits apparent charge injection and migration, leading to the severe electric field distortion of 20%. Noticeable charge accumulation can be observed at the unaged double-layer sample interface due to the mismatching of DC conductivity, which play a significant role in the aged double-layer samples. This work utilizes precise thermal analysis to provide new information about the resistance ability of thermal oxidation of LDPE, FPE, and HDPE, and its influence on space charge behaviors, which is helpful for the insulation design and evaluation in cable applications. [ABSTRACT FROM AUTHOR]

A composite micro-textured surface structure is proposed and demonstrated to enhance the surface flashover strength of polymer insulators used in vacuum. The structure is fabricated in two stages, with periodic triangular grooves of approximately 210 μm in width formed in the first stage and micro-holes of approximately 2 μm coated on the inner surface of grooves in the second. The aim is to exploit the synergistic effects between the grooves and micro-holes to suppress the secondary electron yield to obtain a better flashover performance. To acquire insulators with the composite micro-textured surface, the CO2 laser processing technique is applied to treat the surface of the PMMA insulators. The test results show that the flashover voltages of the insulators with the two-stage fabricated structure increase by 150% compared with the untreated samples in the best state. Compared with the traditional macro-groove structures on insulators, the proposed composite micro-textured insulators exhibit a better surface flashover performance. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control 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.)

The efficiency of modification of the surface layers of Al-6Mg aluminium alloy by combined treatment, including electric discharge surface alloying (EDSA) with Tungsten and finishing ultrasonic impact treatment (UIT) to improve the microstructure, strength and corrosion properties is analysed. The results of electron microscopic and x-ray structural phase analyses indicate the formation of the surface layer containing Al-W solid solution and Al4W or Al12W intermetallic phases, which cause hardening. Microdurometric analysis shows that the combined (EDSA (W) + UIT) process doubled the microhardness of the surface layers as compared to the initial state. As shown, the modified surface possesses the increased anti-corrosion properties owing to the accelerated formation of the passivating oxide film due to the large number of intergranular and interfacial boundaries. [ABSTRACT FROM AUTHOR]

The high‐frequency power transformer (HFPT) has become a vital component of the power system. For HFPT insulations, surface discharge is a serious problem. Polyimide (PI) is a widely used insulating material for HFPT's. A needle‐plate electrode structure‐based experimental setup was developed to produce and measure the surface discharge. This paper first time used the fluid‐kinetic model by adopting the finite element simulation method to address the micro‐level study of surface discharge. This paper aimed at the discharge phenomenon of the PI under the direct action of high‐frequency sinusoidal voltage and has not considered the overvoltage phenomenon caused by the waveform parameters that is the actual high‐frequency action on the PI material. The development of surface discharge at various stages was analysed. Particle densities and electric field distributions versus discharge time were determined. Frequency, temperature, and air pressure have a significant effect on surface discharge behaviour. As a result, the applied voltage reaches its peak value at high‐frequency, so the flashover time of surface discharge is reduced under the high frequency. The electron density of the streamer development increases as the temperature rises, and the time to flashover the channel becomes shorter. The higher the electron density and the longer the discharge channel develops while the gas pressure is lower. The simulation results have high accuracy and good agreement with experimental data. [ABSTRACT FROM AUTHOR]

The impact of the electrode proximity on the streamer breakdown and development of pulsed-driven dielectric barrier discharges (DBDs) in a single-filament arrangement has been investigated in a gas mixture of 0.1 vol% O2 in N2 at 0.6Â bar and 1.0Â bar. The gap distance was varied from 0.5Â mm to 1.5Â mm, and the applied voltage was adapted correspondingly to create comparable breakdown conditions in the gap. The development of the DBDs was recorded by an iCCD and a streak camera system, while fast electrical measurements provided insight into discharge characteristics such as the transferred charge and consumed energy. The results demonstrate that breakdown in a smaller gap is characterised by a slower streamer propagation but a significantly higher acceleration. It can therefore be concluded that the proximity of the cathode has a strong impact on the characteristics of the streamer breakdown. However, after the streamer has crossed the gap, the discharge structure in front of the anode was found to be the same independent of the actual gap distance. [ABSTRACT FROM AUTHOR]

The microstructure, hardening and corrosion properties of the surface layers of aluminium alloy AMg6, modified by ultrasonic impact treatment (UIT) and by complex treatment, which combined electric discharge surface alloying (EDSA) with titanium and UIT, are analyzed. X-ray diffraction phase analysis and transmission electron microscopy showed that the combined treatment (EIL  UIT) leads to a double increase in microhardness compared to UIT due to the formation of a TiAl solid solution and TixAly intermetallic phases, as well as some quantity of oxides. The EDSA  UIT process leads to the highest corrosion resistance of AMg6 alloy in aqueous solution of 3.5% NaCl, which is manifested itself in an increase in the corrosion potential by 40-70 mV as compared to that registered for the sample after UIT, due to the formed structural-phase state of the modified surface. [ABSTRACT FROM AUTHOR]

This study examines the effect of airflow orientation with respect to the strip active electrode on concentration of ozone and nitrogen dioxide produced in a planar generator based on the surface dielectric barrier discharge. The orientation of the airflow was tested in parallel and perpendicular with respect to the strips. It was found that in the investigated range of average discharge power, the ozone concentration increases approximately by 25% when airflow was oriented in parallel with respect to the strips in comparison with perpendicular orientation of the airflow. Similarly the increase of nitrogen dioxide concentration was observed for parallel orientation of the airflow with respect to the strips in comparison with the perpendicular orientation of the airflow. Within the range of wavelengths from 250 to 1100 nm, the changes of intensities of spectral lines associated with airflow orientation have been observed. A 3D numerical model describing ion trajectories and airflow patterns have also been developed. [ABSTRACT FROM AUTHOR]

In this paper, an advanced surface-grafting method is reported to improve the high-temperature performance of biaxially oriented polypropylene (BOPP) membranes. The leakage conductivity of the surface-grafted films decreases by 98% at 85 °C. The decline in the leakage loss contributes to the 99% charge-efficiency at 85 °C. The dielectric constant increases by 7%. The DC breakdown strength grows by 43% at 85 °C. The maximum energy storage density goes up from 1.45 to 2.77 J/cm3 at 85 °C. The surface-grafted BOPP film exhibits outstanding energy density and charge-discharge efficiency characteristics. This research provides a theoretical reference for improving the performance of capacitor film based on surface modification. [ABSTRACT FROM AUTHOR]

Modern electrified transportation systems feature increasing installed power and performance and correspondingly stray current phenomena and corrosion are receiving more attention in terms of contractual specifications and request of final validation of proposed solutions, as well as a maintenance program that can actively tackle stray current issues. The problem is complex for the system physical extension, difficult measurement conditions and variability of electrical parameters. This work considers validation of stray current protection performance, in terms of track voltage, track leakage and collected current, and impressed potential on structures along the right-ofway. The exemplification of the specifications of a hypothetical instrument and setup support the discussion. [ABSTRACT FROM AUTHOR]

SnO2–ZnO thin films consisting of nanoscale crystallites were obtained on glass and silicon substrates by solid-phase low-temperature pyrolysis. The synthesized materials were studied by XRD and SEM methods, electrophysical and optical properties were evaluated, as well as the band gap was calculated. It was shown that regardless of the phase composition all films were optically transparent in the visible range (310–1000 nm). The nanocrystallites' minimum size, the highest activation energy of the conductivity and the smallest band gap calculated for indirect transitions were shown for a thin film 50SnO2–50ZnO. It was assumed that the band gap decreasing might be attributed to the existence of surface electric fields with a strength higher than 4 × 105 V/cm. [ABSTRACT FROM AUTHOR]

This study investigates the effects of voltage rise rates from 0.1 kV ns−1 to 100 kV ns−1 on streamer discharge in air at atmospheric pressure using numerical simulation. The curvature of the needle electrode is also used as an input parameter to change the streamer inception voltage and the average voltage, Vave, during streamer propagation. The results show that the streamer propagation velocity, vpri, the electric field strength at the streamer head, Eh, the diameter of the streamer channel, and the O radical production characteristics during the primary streamer propagation are dependent on Vave. vpri and Eh exhibit different effects on Vave/d, where d is the gap distance of the electrode, which indicates that the streamer remains in the transient state from the filament-type discharge to the diffuse-type discharge. The comparison between the simulation and experimental results shows that the simulated vpri characteristics are in good agreement with the experimental results, regardless of the voltage waveform and electrode configuration, which indicates that Vave/d has a strong correlation with the primary streamer characteristics. [ABSTRACT FROM AUTHOR]

The 205 Ma Rochechouart impact structure (France) is characterized by various impactite formations overlying the Hercynian crystalline basement. New constraints from downhole logging and surface electrical resistivity measurements along >100 m long profiles reveal that the top melt‐bearing breccia layer is more conductive and porous than the underlying melt‐poor breccia layer. The stratigraphy within the impactite and the transition with the basement are irregular at small (∼1–10 m) and medium (>100 m) scales, with vertical amplitude up to 40–50 m. At larger scale (>1 km), audio‐magnetotelluric observations are able to map the lateral and vertical extent of fracturing/brecciation in the basement, reaching 200 m below the surface nearby Chassenon, in the northern part of the structure. Our results also unveil that the impactite deposits and the brecciated basement of the Rochechouart impact structure may have been shifted laterally and vertically during the modification stage of the impact event through displacements of megablocks, which may be associated with the collapse of a central uplift. Plain Language Summary: The geological formations of the Rochechouart impact structure are mapped using geoelectrical measurements. The electrical properties of impacted rocks differ significantly from the non‐impacted rocks, thus allowing the imaging of the geological contrasts. Our geophysical study reveals the complex topography of the transition between the impactite and the crystalline basement formations at the bottom of such medium‐size impact structure. The lateral and vertical extent of brecciation/fracturation is also investigated using this method, unveiling possible megablocks emplacement throughout a general northward tilting of the crater, which challenges the expected structure of the crater. Key Points: All impactite formations of the Rochechouart impact structure have a clear electrical signatureLarge‐scale electrical investigations unveil a rough transition between impactites and unbrecciated basement, implying possible megablocksFracturing/brecciation in the Rochechouart basement locally reaches depths larger than 200 m [ABSTRACT FROM AUTHOR]

This paper is an experimental study of the electrical conduction of mineral-oil/solid interfaces in negative polarity. This study is performed in a point-plane configuration immersed in mineral oil submitted to impulse voltages. The interface is assembled with an inclined solid in contact with the point electrode tip. Charge recordings and conduction currents of different combinations of mineral-oil/solid interfaces are reported. Different polymers and oil-impregnated papers are used as the solid materials. It is found that for voltages lower than the inception voltage, the injection of charge belongs to a weak injection regime. The spatial limitation with solids of similar permittivity as the mineral oil decreases the charge injection. The charge injection at mineral-oil/solid interfaces follow two conduction current type characteristics. Experiments with mineral-oil/PTFE interface shows the existence of a transition between both conduction current types if the applied voltage is increased. [ABSTRACT FROM AUTHOR]

The primary aims of this paper are to provide a better understanding of surface dielectric barrier discharge based on annular geometry and to investigate the effect of segmented grounding electrodes on their electrical and optical properties. To this end, four grounding electrode conditions are considered: 10-segment, 20-segment, and 30-segment ones as the experimental conditions, and an unsegmented (termed 0-segment) one as the control. A great number of current pulses with lower amplitudes are observed under the segmented conditions compared to the 0-segment condition. In the former case, the current pulse number and the peak value are observed to be inversely and directly proportional to the number of segments, respectively. However, the average currents corresponding to the various segmentations are observed to be nearly identical, and each of them is lower than that under the 0-segment condition. Secondly, the discharge uniformity under the 30-segment condition is observed to be better than under the 0-segment condition, because even though the discharge is usually concentrated at covered regions, it spreads spanwise to the adjacent uncovered regions as the number of segments is increased. Consequently, the airflow induced by spanwise-spread plasma extends the effective range of plasma action. Moreover, the Lissajous figures corresponding to the four conditions are ascertained to be approximately parallelogram-shaped. However, the slopes of the discharge phases are dependent on the voltage, as the variations of equivalent capacitance in dark and discharge phases are distinct. A higher amount of power is consumed under the 30-segment condition than under the 0-segment condition, although the maximum transported charge is much lower in the former case. Finally, in the quasi-sinusoidal external electric field distribution induced by the segmented grounding electrode, a slightly lower-than-average electric fields avoid the creation of obvious separated channels, while a moderate peak-to-peak difference of electric field improves the electric field distortions caused by existing micro-discharges. This phenomenon serves as a satisfactory explanation of the differences between the discharge channel developments and the plasma distributions under different conditions. Based on the obtained results, we conclude that the performance of discharge plasma can be improved by arranging the electrodes optimally. [ABSTRACT FROM AUTHOR]

The propagation mechanisms of plasma streamers have been observed and investigated in a surface dielectric barrier discharge (SDBD) using 2D particle in cell simulations. The investigations are carried out under a simulated air mixture, 80% N2 and 20% O2, at atmospheric pressure, 100 kPa, under both DC conditions and a pulsed DC waveform that represent AC conditions. The simulated geometry is a simplification of the symmetric and fully exposed SDBD resulting in the simultaneous ignition of both positive and negative streamers on either side of the Al2O3 dielectric barrier. In order to determine the interactivity of the two streamers, the propagation behavior for the positive and negative streamers are investigated both independently and simultaneously under identical constant voltage conditions. An additional focus is implored under a fast sub nanosecond rise time square voltage pulse alternating between positive and negative voltage conditions, thus providing insight into the dynamics of the streamers under alternating polarity switches. It is shown that the simultaneous ignition of both streamers, as well as using the pulsed DC conditions, providing both an enhanced discharge and an increased surface coverage. It is also shown that additional streamer branching may occur in a cross section that is difficult to experimentally observe. The enhanced discharge and surface coverage may be beneficial to many applications such as, but are not limited to: air purification, volatile organic compound removal, and plasma enhanced catalysis. [ABSTRACT FROM AUTHOR]

In the past, the effect of electrical parameters, dielectric, and electrode material and shape on surface integrity in electric discharge machining (EDM) was widely studied by scholars. However, these researches are mainly based on single-step EDM that can be categorized into either roughing or finishing. The production of components by EDM is a process from roughing to finishing in industry, which is a multi-step machining process. Therefore, in order to provide a better guideline for the fabrication of parts through the single-step EDM approach (refers to the last step of multi-step machining in this study), it is necessary to investigate and quantify the difference in surface integrity between single-step and multi-step sequential machining. In this study, the surface integrity of single-step and multi-step machined samples is evaluated and compared. The results demonstrate that the surface roughness, white layer thickness, and surface residual stress of multi-step machined samples are higher than those of single-step machined samples. In the finishing stage, the difference in surface roughness and residual stress between them becomes even larger. It was indicated that the surface state of the sample obtained in the previous processing steps has an influence on the final machining quality during multi-step sequential EDM. In addition, the change of the surface morphology of the tool electrode caused by the previous machining steps would also affect the surface roughness of the workpiece processed in the current step. There is no significant difference in the crystalline phase between single-step and multi-step sequential machining. [ABSTRACT FROM AUTHOR]

In this study, the temporal variation of an electric potential distribution was measured in a surface dielectric barrier discharge experiment using the Pockels effect. A branching pattern and homogeneous distribution were respectively observed when positive and negative voltages were applied. When continuous alternating current was applied to the electrode, the spatial distributions of the electric potential significantly changed between the first and subsequent discharge cycles. The results indicate that the electrostatic repulsive forces caused by the residual charges on the dielectric surface affect the dynamic patterns of the discharge morphology. [ABSTRACT FROM AUTHOR]

The spatiotemporal dynamics of volume and surface positive and negative streamers in a pin‐to‐plate volume dielectric barrier discharge is investigated in this study. The discharge characteristics are found to be completely different for positive and negative streamers. First, the spatial propagation of a positive streamer is found to rely on electron avalanches caused by photoelectrons in front of the streamer head, whereas this is not the case for negative streamers. Second, our simulations reveal an interesting phenomenon of floating positive surface discharges, which develop when a positive streamer reaches a dielectric wall and which explain the experimentally observed branching characteristics. Third, we report for the first time, the interactions between a positive streamer and dielectric pores, in which both the pore diameter and depth affect the evolution of a positive streamer. [ABSTRACT FROM AUTHOR]

The properties of water surface discharge plasma for variety of pulse repetition rates are investigated. A magnetic pulse compression (MPC) pulsed power modulator able to deliver pulse repetition rates up to 1000 Hz, with 0.5 J per pulse energy output at 25 kV, was used as the pulsed power source. Positive pulse with a point-to-plane electrode configuration was used for the experiments. The concentration and production yield of hydrogen peroxide (H2O2) were quantitatively measured and orange II organic dye was treated, to evaluate the chemical properties of the discharge reactor. Experimental results show that the physical and chemical properties of water surface discharge are not influenced by pulse repetition rate, very different from those observed for under water discharge. The production yield of H2O2 and degradation rate per pulse of the dye did not significantly vary at different pulse repetition rates under a constant discharge mode on water surface. In addition, the solution temperature, pH, and conductivity for both water surface and underwater discharge reactors were measured to compare their plasma properties for different pulse repetition rates. The results confirm that surface discharge can be employed at high pulse repetition rates as a reliable and advantageous method for industrial and environmental decontamination applications. [ABSTRACT FROM AUTHOR]

Ionic wind devices or electrostatic fluid accelerators are becoming of increasing interest as tools for thermal management, in particular for semiconductor devices. In this work, we present a numerical model for predicting the performance of such devices; its main benefit is the ability to accurately predict the amount of charge injected from the corona electrode. Our multiphysics numerical model consists of a highly nonlinear, strongly coupled set of partial differential equations including the Navier-Stokes equations for fluid flow, Poisson's equation for electrostatic potential, charge continuity, and heat transfer equations. To solve this system we employ a staggered solution algorithm that generalizes Gummel's algorithm for charge transport in semiconductors. Predictions of our simulations are verified and validated by comparison with experimental measurements of integral physical quantities, which are shown to closely match. [ABSTRACT FROM AUTHOR]

The evolution of a microsecond pulsed barrier discharge initiated in atmospheric pressure air in the point–plane electrode geometry has been investigated using streak camera photorecording and shadow photography with micrometer resolution and nanosecond exposure. It has been shown that the discharge develops in series and its structure evolves both within a series and from series to series. It has been found that, irrespective of the polarity of a feed voltage pulse, the discharge develops from the point electrode, having the form of a set of many micrometer-diameter channels. At the late stage, the discharge consists of a number of glowing microstructured channels, which occupy the space between the point and barrier and deviate from the point axis, and many faint channels radially propagating over the surface of the barrier. Numerical parameters of the structured have been obtained. [ABSTRACT FROM AUTHOR]

We report on a detailed numerical study of the two-phase operation of a surface alternating current dielectric barrier discharge actuator. We showcase that when the quasi-periodic regime has been established, residual volume and surface charges play an important role on the discharge evolution strongly coupling the positive and negative phases. It is shown that the quasi-neutral streamer discharge found on the positive phase serves as both a positive and negative charge generator and acts as a virtual anode. As the streamer is not attached to the dielectric surface, most of the surface charging occurs during its after-burn (relaxation) phase. The positive surface charge leads to an distant zone of high electric field and thus ion drift but also interacts majorly with the negative discharge phase. During the latter, microdischarges form near the active electrode and an intense cathode layer feeds with charges the discharge volume. Each microdischarge is followed by a plasma layer formation attached to the dielectric layer expanding further at each repetition until it occupies a volume linked to the streamer elongation length and positively charged surface portion. The strong coupling between the positive and negative phases along with the strong impact of the streamer discharge on both suggest implications that have been ignored so far in terms of electrohydrodynamic force production and its spatiotemporal distribution. [ABSTRACT FROM AUTHOR]

This study focuses on the feature extraction and classification of surface discharges of ice-covered insulator strings during process of alternating current flashover. The test specimen was the five units suspension ceramic insulators, which was artificially accreted with wet-grown ice in the cold-climate room of CIGELE. Based on the IEEE Standard 1783/2009, flashover experiments were conducted on iced insulators to measure the minimum flashover voltage (VMF) and record the propagating process of surface discharges to flashover by using a high-speed video camera. The gray-level co-occurrence matrix (GLCM) method has been used to extract four parameters of arc discharge images features that characterize different stages of flashover process. The parameters are angular second moment (ASM), contrast (CON), inverse difference moment (IDM) and entropy (ENT). These statistical parameters of GLCM can be extracted to reveal the underlying properties of ice flashover on the insulator surface from the quantitative perspective. The different values of these indicators are representative of the different stages in the process of arc discharge. Once the value of quantitative indicators (ASM, CON, IDM, ENT) of surface discharges exceeds the threshold value, the higher flashover risk of iced insulators will appear. Hence, the proposed methods are helpful to understand and monitor surface discharge on iced outdoor insulator strings for preventing flashover accidents. [ABSTRACT FROM AUTHOR]

On the basis of a unipolar corona discharge, a method of non-contact and continuous measurement of linear parameters of thin and ultra-thin dielectric fibres and optical fibres (10 to 125 microns) in the process of their manufacture was developed. The measurement method differs from the commonly known methods by high accuracy and reliability of measurement and resistance to changes in the electrical characteristics of the discharge gap and the state of ambient air. [ABSTRACT FROM AUTHOR]

The proposed study compares the electrical, thermal and mechanical performances of thermally aged cellulose pressboard material impregnated in mineral oil, synthetic ester fluid and mixed oil. The electrical insulation characteristics of oil‐impregnated pressboard (OIP) are studied by means of surface discharge inception voltage (SDIV) using an ultra‐high frequency technique and surface potential measurement analysis. It indicates that OIP aged in mineral oil has higher surface potential due to higher charge trap density compared to that of the mixed oil and synthetic ester fluid. Mechanical and thermal characteristics of the aged OIP are studied by means of tensile strength measurement and thermo‐gravimetric analysis, respectively. The change in the chemical composition of OIP is studied by means of laser‐induced breakdown spectroscopy, which indicates lower plasma temperature with mineral oil‐based OIP indicating higher degradation state. To further understand the microscopic structure of the thermally aged OIP in different oils, scanning electron microscopy and X‐ray diffraction studies have been performed. The pressboard thermally aged in synthetic ester fluid and the mixed oil has better electrical, thermal and mechanical properties as compared with the pressboard aged in mineral oil. [ABSTRACT FROM AUTHOR]

Dielectric barrier discharges (DBDs) are characterized by electrical measurements interpreted on the basis of equivalent circuits. The concept of the simplest equivalent circuit of volume DBDs is expanded to surface DBDs (SDBDs); this was completed by taking into account the discharge expansion on the dielectric-gas interface. It is assumed, that this expansion is not limited by the dimension of the electrodes. This approach delivers an analytical relationship for the dissipated power as a function of the applied voltage amplitude. It applies to SDBDs with sufficiently long embedded electrodes and operated by sinusoidal high voltages. The obtained relations were validated by comparison with experimental data obtained from previous work devoted to SDBDs with 20 mm elongated electrodes operated in ambient air and for applied peak-to-peak voltages of up to 20 kV at 1 kHz frequency. The dependencies derived from the equivalent circuit agree well with experimentally recorded charge and dissipated energy. [ABSTRACT FROM AUTHOR]