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In this paper investigates the Methylene Blue degradation using two common reactors: the nanosecond pulsed discharge in oxygen bubbles and the Argon Microwave plasma jet above the treated solution. The aim of this study is to compare the evolution of the reactors' performance when the electrical conductivity increases. In deionized water, the Methylene Blue degradation and the energy efficiency in the nanosecond pulsed discharge configuration were significantly higher than the Argon microwave plasma jet. However, when the solution electrical conductivity is increased, the energy efficiency of the nanosecond pulsed discharge drops significantly by ~82%, whereas the performance of the microwave plasma jet reactors decreases by ~37% only for a greater variation of the electrical conductivity of the solution. Under these conditions, the efficiency of both reactors becomes comparable, suggesting the necessity to consider various parameters to compare the reactors' efficiency.

The reduced electric field E/N is one of the important parameters for understanding the occurrence, propagation, state, and plasma chemical reaction of discharge and plasma phenomena. The measurement of the E/N using the nitrogen emission intensity ratio has been used to help understand various discharge and plasma phenomena. Among various discharge and plasma phenomena, nanosecond pulsed discharges are expected to be used in gas processing, environmental purification, surface treatment, agriculture, and medical applications. However, the E/N of nanosecond pulsed discharges with very short pulse widths has not been clarified. In this work, the intensity ratio of nitrogen is used to investigate the E/N of primary and secondary streamer discharges nanosecond pulses generated between a coaxial cylindrical reactor in terms of spatial, temporal, and voltage dependence. Therefore, the maximum E/N of the positive nanosecond pulsed primary streamer discharge generated at the center of the electrode was 522–834 Td. The E/N at the coaxial cylinder's center was also higher than the E/N near the outer electrode. As the applied voltage increased, the E/N of nanosecond pulsed discharges also increased. From these results, the reasons why nanosecond pulse discharges are effective in applications (ex. Ozone generation and NO x treatment) are discussed. [ABSTRACT FROM AUTHOR]

The efficient removal of low‐concentration endocrine disruptors is crucial for the protection of the aquatic environment. In this study, porous polymer adsorbent materials were modified by nanosecond pulsed discharge plasma to achieve efficient adsorption of low‐concentration bisphenol A (BPA). The removal efficiency of BPA reached 99% after 10 min of plasma modification at a pulse peak voltage of 28 kV, which increased by 25.8% compared to the raw materials. This enhancement was attributed to the increase of active sites and oxygen‐containing functional groups. The adsorption behaviors of the porous polymer materials were primarily dominated by monolayer chemisorption. Subsequently, comparative experiments further verified the high‐efficiency adsorption performance of porous polymer materials after plasma treatment. [ABSTRACT FROM AUTHOR]

Plasma fluidized-bed contributes to strengthening the interaction between active species in plasma and fluidized powder particles, resulting in higher active species utilization efficiency and superior powders processing/modification performance. However, the plasma streamer dynamics on the fluidized powder particles are still unclear due to the intricacy of plasma fluidized-bed. In this work, the time-resolved evolution behavior of plasma streamers on fluidized powder particles surfaces has been explored in plasma fluidized-bed system based on a simplified pin-cylinder configuration. The results reveal that the entire streamer propagation process includes volume discharge and surface discharge. The maximum electron density generated by surface discharge is one order of magnitude higher than that produced by volume discharge, indicating that surface discharge plays a dominant role in powder particles modification. The presence of fluidized particle will cause streamer branching, and the main streamer splits into two independent sub-streamers for propagation in a 'parabola-like' shape. Compared with large-size fluidized particles (1000 µ m), streamer wraps a larger area on micron-size fluidized particles (200 µ m), with a 78% increase in the coverage area, which is favorable to the modification of powder particles. Furthermore, the evolution of active species on fluidized particle surface is analyzed. The active species (N, O, O2−) are mainly distributed around the north pole, and N2+ is mainly distributed between 25° and 50° of the particles. With the decrease of fluidized particle size, the polarization effect between particles is significantly enhanced, and the maxima of the number densities of active species increase. These findings help to get a better understanding of the interaction between plasma and fluidized particles in fluidized systems. [ABSTRACT FROM AUTHOR]

Non-thermal plasma coupling with photocatalyst is recognized as a promising technology for the degradation of antibiotics, and improving the photocatalyst performance is one of the most significant strategies to improve the efficiency of plasma-catalytic systems. This study employed a nanosecond pulsed gas–liquid discharge coupled with plasma-functionalized TiO2 to achieve a high efficiency of tetracycline degradation and clarify the synergistic mechanism of nanosecond pulse discharge coupling with functionalized TiO2. Results showed that the degradation efficiency with functionalized TiO2 increased by 20% compared to the untreated TiO2 for 4 min-plasma treatment. It is also suggested that the effect of photogenerated holes and electrons can be promoted in the functionalized TiO2, as evidenced by the radical quenching experiments. The plasma-modified TiO2 catalysts were proven to have a good stability and recyclability. This study provides a new sustainable approach to enhance the performance of photocatalysts in the plasma system for environmental remediation. [ABSTRACT FROM AUTHOR]

This article proposes a 0D model for Nanosecond Pulsed Discharges (NPD). The model incorporates the high-frequency transmission line, a lumped equivalent circuit for the load, a two-temperature model for heavy particles and electrons, and an ionization scheme. The load impedance is modeled as a stray capacitance in parallel with a stray inductance and a time-varying electrical resistance, which depends on the plasma radius and electron number density. The ionization mechanism used to simulate the electron number density includes the impact ionization of N2 and O2 and two- and three-body attachments on O2, all dependent on the applied electric field and gas temperature. The temperature variation is calculated using the energy conservation equation, with electrical power as the source. The model is tested against current and voltage measurements of NPDs in sub-mm gaps at pressures ranging from 2 to 8 bar. The comparison of simulation results with experimental data shows that the plasma’s electrical resistance rapidly drops to low values within approximately 1–2 ns after breakdown. This drop is attributed to the formation of a fully ionized micrometer-sized thermal spark, a conclusion supported by optical emission spectroscopy measurements. This model is intended for experimental plasma researchers seeking a simple tool to understand plasma states through basic electrical measurements and for electrical engineers needing insights into varying load impedance, a crucial parameter for pulse generator design.

A porous functionalized resin was produced using nanosecond pulsed discharge for the purpose of removing Ni(II). The implications of discharge time, O2 concentration, and solution pH on adsorption capacity were explored. Studies indicated that nanosecond pulsed discharge‐modified resins in 5 min of discharge time and 8% of O2 concentration had a removal efficiency of 97.2%, and an increase of 36% compared to the raw. Furthermore, the residual Ni(II) concentration (0.3 mg/L) is well below the national permitted emission standard (0.5 mg/L). The rise in Ni(II) removal efficiency is associated with the increased specific surface area and oxygen‐containing functional groups. Chemisorption played an important role in the removal of Ni(II) by raw and modified resins. [ABSTRACT FROM AUTHOR]

This work investigates the temporal dynamics of O atoms in nonequilibrium atmospheric pressure plasma (NAPP) generated by kHz nanosecond pulsed discharge. Two‐photon laser‐induced fluorescence (TALIF) method is used to measure the time resolution of O atom density from the first discharge pulse in two gas mixtures, He + 0.4%O2 and He + 0.4%air. The discharge frequencies of 1 and 10 kHz are considered in the experiment. The results show that the O atom density does not accumulate with increasing number of pulses in both gas environments at 1 kHz. However, at 10 kHz, a cumulative effect of O atom density with the number of pulses is observed in both gas mixtures. After 10 and 300 discharge pulses in He + 0.4%O2 and He + 0.4%air, respectively, the O atom density saturates at the same moment after each discharge cycle. It was found that even after a long operating period of discharge, the decay of O atom density during each discharge cycle is not negligible. The O atom density in He + 0.4%O2 varies in the range of 2.85 × 1021 m−3–4.29 × 1021 m−3 while the O atom density in He + 0.4%air varies in the range of 2.60 × 1021 m−3–3.19 × 1021 m−3. This indicates that the choice of diagnostic time points is important for the O atom density measurements when using TALIF to diagnose kHz pulsed NAPP. In addition, 0D plasma chemical kinetics models are developed for the two gas mixtures to investigate O atoms' production and consumption processes. The causes of the cumulative effect of O atom density at 10 kHz, the saturation effect, and the formation of the periodic variation trend are also investigated. The simulation results show that the consumption rate of O atoms and the O atom density are directly correlated. As the number of pulses increases, the O atom consumption rate increases, which gradually counteracts the number of O atoms generated during the pulse discharge. This leads to delay and saturation of the cumulative effect of O atoms. [ABSTRACT FROM AUTHOR]

This work presents a simplified methodology for coupling the physics of a nanosecond-pulsed discharge to the process of supersonic combustion within a backward-facing step combustor. The phenomena of plasma and supersonic combustion are simulated separately and then coupled. Based on results reported in the literature, a zero-dimensional plasma model is built, considering only the kinetic effects of the nanosecond-pulsed discharge. A set of Favre-averaged compressible Navier-Stokes equations, as well as finite rate chemistry, is used in the combustion model and solved with a control-volume based technique. The plasma-supersonic combustion coupling process only considers the discharge as a source of O and H radical species. The calculated densities of the radicals generated during each pulse from the plasma model are periodically seeded inside the domain of the combustor. The proposed methodology is used to perform a novel simulation that involved the application of plasma to a well-known supersonic combustion experiment. The temperature and species concentration contours show that the proposed methodology captures the main effects of the nanosecond-pulsed discharge on supersonic combustion. The ignition delay time is reduced when the plasma discharge was applied. In addition, the simulations show that the plasma causes a supersonic low-enthalpy mixture to ignite, confirming the capability of the methodology.

In this work, a nanosecond pulsed packed‐bed discharge (PBD) plasma was developed for SF6 degradation under different dilution gases. The discharge form transfers from filamentary discharge to the combination of surface discharge and microdischarge after introducing the packing material regardless of the dilution gas used, and the local electric field strength and SF6 degradation performance are promoted. The mean electron energy and rate coefficient for SF6 excitation in SF6/Ar system are significantly higher than those in SF6/N2 or SF6/air system, which results in higher SF6 degradation efficiency in SF6/Ar system. Moreover, the response surface methodology based on the Box–Behnken design model was constructed to optimize several key process parameters including pulsed voltage, gas flow rate, oxygen content, and relative humidity, as well as assess the contribution of each parameter to SF6 degradation. The proposed optimization model shows a satisfactory correlation between the predicted and the experimental results. The energy yield concerning SF6 degradation in nanosecond pulsed PBD plasma achieves approximately 75.3 g/kWh with nearly complete degradation. This work is expected to provide an efficient and energy‐saving plasma technique for SF6 degradation. [ABSTRACT FROM AUTHOR]

Ammonia (NH3 ) as an important chemical raw material has a direct influence on the development of agriculture, national economy and people's livelihood. It is a high temperature, high pressure, high energy consumption and heavy pollution process in the industrial synthesis of ammonia. Low-temperature plasma technology is a sustainable and promising technology for ammonia synthesis, which has become a research hotspot at home and abroad. In this work, nitrogen and hydrogen are used as raw materials, and nanosecond pulsed dielectric barrier discharge is used to synthesize ammonia at low temperature and atmospheric pressure. The effects of factors such as pulse peak voltage, pulse repetition frequency, total gas flow rate, and N2 ∶H2 volume ratio on the synthesis rate and energy yield of ammonia synthesis are investigated systematically through a single-factor experiment. Furthermore, through the orthogonal experimental evaluation, it is determined that the order of factors affecting the synthesis rate is: pulse peak voltage>pulse repetition frequency>gas volume ratio>gas total flow rate. The order of factors affecting the energy yield is: pulse peak voltage>gas volume ratio>pulse repetition frequency>total gas flow rate. Combined with these two parts of experiments, the optimal conditions for ammonia synthesis are finally obtained: Pulse peak voltage 16 kV, pulse repetition frequency 6 kHz, pulse rising edge 100 ns, V (N2 ) ∶V (H2 ) =1∶1, and total gas flow rate 200 mL/min. Under this condition, the highest NH3 synthesis rate is up to 923. 08 μmol/h and the energy yield is 0. 30 g/kWh, respectively. [ABSTRACT FROM AUTHOR]

Surface charges have significant impact on the evolution of surface dielectric barrier discharge (SDBD). In this work, the role of residual surface charges on repetitively nanosecond pulsed SDBD in atmospheric air is investigated using a two-dimensional fluid model, based on the assumption of preserving the distribution of surface charges at the end of the previous high voltage (HV) pulse. In the bipolar mode when the polarity of residual surface charges is opposite to that of the current HV pulse, a lower breakdown voltage and more deposited energy can be observed, showing an obvious enhancement of SDBD. In the unipolar mode, residual surface charges suppress the development of discharges and energy deposition. It is found that more residual surface charges are accumulated during the negative pulsed discharge, which have a more pronounced effect on the subsequent positive pulsed one. This is explained by the fact that the negative surface streamers directly contact the dielectric and charge it, while the positive surface streamers float above the dielectric, forming a ion-rich region near the surface. The results in this work demonstrate the mechanism of how residual surface charges affect discharge dynamics, which can be utilized to regulate energy deposition in SDBDs. [ABSTRACT FROM AUTHOR]

The single‐step conversion of CH4 to higher alcohols without catalyst or complex processing is the dream solution both in C1 chemistry and the chemical industry. Here, an innovative synthesis of higher alcohols from CH4–CH3OH was driven by a highly flexible nanosecond pulsed plasma. Experimental results showed that the products distribution was strongly correlated with the electric field variation and reactants composition, and the maximum conversion of CH4 (35.9%) and CH3OH (77.4%) were obtained at the CH4/Ar ratio of 1:2. Interestingly, the addition of H2O and H2O2 effectively promoted the C2–C4 alcohols selectivity up to 19.4%. In addition, optical diagnostics were used to obtain active species distribution and integrated insights into the C–C coupling of higher alcohols generation. A possible reaction mechanism of CH4–CH3OH plasma was also discussed. [ABSTRACT FROM AUTHOR]

A theoretical analysis of excited argon state densities responsible for optical emission spectra of atmospheric pressure argon plasma is presented for its use in plasma diagnostics. Nanosecond pulsed barrier discharges are simulated using spatially one- and two-dimensional fluid-Poisson models using the reaction kinetics model presented by Stankov et al. [ 1 ], which considers all ten argon 2p states (Paschen notation) separately. The very first (single) discharge and repetitive discharges with frequencies from 5 kHz to 100 kHz are considered. A semi-automated procedure is utilized to find appropriate 2p states for electric field determination using an intensity ratio method, which is based on a time-dependent collisional-radiative model. The fluid simulations in combination with the semi-automated procedure are used to quantify the sensitivity of selected 2p-state ratios to given preionization of the gas. A highly sensitive time-correlated single photon counting experiment shows clearly that the selected ratio is sensitive to the electric field variation in the streamer head, yet additional calibration is needed for absolute values determination. Different approaches for effective lifetime determination are tested and applied also to measured data. The influence of radial and axial 2p state density integration on the intensity ratio method is discussed. The above mentioned models and procedures result in a flexible theory-based methodology applicable for development of new diagnostic techniques. [Display omitted] • Nanosecond argon plasmas need effective diagnostic methods for electric field determination. • Most accessible intensively emitting 2p states usually disregarded yet found applicable here. • Combination of 2D simulations and sub-nanosecond spectroscopy as state-of-the-art methodology. • Semi-automated procedure finds sensitive intensity ratios for electric field diagnostics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Non-equilibrium plasma ignition technology can improve ignition stability and combustion efficiency. • The ignition and combustion assistance effects of NH 3 /air mixture in CVCC are studied using high-frequency nSDBD. • The effect of high-frequency nSDBD on the growth process of the flame kernels in NH 3 /air mixtures is revealed. • The effect of discharge frequency on FDT and FRT exhibits a non-monotonic variation pattern. Non-equilibrium plasma ignition technology, with its ability to expand ignition limits and increase ignition volume, is considered an important development direction of advanced ignition systems, and has significant advantages in improving ignition stability and combustion rate. This study investigates the ignition and combustion assistance effect of high-frequency nanosecond surface dielectric barrier discharge (nSDBD) on NH 3 /air mixture in a constant volume combustion chamber (CVCC). The study reveals the influence of high-frequency nSDBD on the growth process of the flame kernel in NH 3 /air mixture. As the discharge pulse number (PN) increases, the flame kernel develops from the middle position of the discharge filament to the head of the discharge filament, while there is no obvious flame at the root and middle of the discharge filament. Continuous discharge causes the flame kernel to appear concave and the center of the flame kernel to shift towards the wall of the CVCC. In the NH 3 /air mixture, the initial flame kernels exhibit dissipation phenomenon, resulting in a discrepancy between the number of initial flame kernels and the number of stable combustion flame kernels. As the discharge frequency or pulse number increases, and the number of stable combustion flame kernel increases. The adjustment of discharge frequency and pulse number can effectively control the flame development time (FDT) and flame rise time (FRT) of NH 3 /air mixture. As PN increases, both FDT and FRT are shortened. When discharge frequency is 20 kHz, the maximum shortening of FDT and FRT are 30 ms and 14 ms, respectively, about 55 % and 30 %. The effects of discharge frequency on FDT and FRT exhibit a non-monotonic variation pattern, and it is necessary to comprehensively consider various discharge parameters to achieve the best ignition effect. The ignition success rate curve of high-frequency nSDBD in NH 3 /air mixture is steep. The study results of this paper provide new discoveries and experimental data for advanced ignition systems. [ABSTRACT FROM AUTHOR]

Non-equilibrium plasma has been proven to expand ignition limits and enhance combustion. This paper uses high-voltage nanosecond pulsed discharge (NPD) to generate non-equilibrium plasma and experimentally studies the discharge characteristics at different parameters in a constant-volume combustion bomb. NPD is used to ignite the methane-air mixture, and the effects of pulse power output voltage and pulse interval (PI) on ignition and combustion processes are studied. In addition, the minimum ignition energy (MIE) at different ignition methods (Transistor coil ignition (TCI) and NPD) is also studied. The results show that the first pulse of NPD discharge has a higher breakdown voltage and discharge energy when using multi-pulse discharge. After the second pulse, the highest breakdown voltage and current tend to stabilize, and the discharge energy remains unchanged. As the PI increases, the breakdown peak voltage and the peak current increase slightly. The study on the MIE of NPD shows that at different mixture concentrations, the MIE of NPD is smaller than that of TCI, and NPD can expand the lean burn limit. An increase in initial temperature can significantly reduce MIE. In addition, when the discharge energy is near the MIE, the combustion stability begins to decrease, and the combustion cycle fluctuates wildly. When the ignition energy is increased, the stability improves, and the combustion fluctuation rate can be maintained within 5%. [Display omitted] • The breakdown voltage and current characteristics of NPD at different discharge parameters are investigated. • Minimum ignition energy is studied for different ignition methods. • At the same parameters, the discharge energy of the hundred-nanosecond pulse is higher than that of the ten-nanosecond pulse. • At different mixture concentrations, the MIE of NPD is smaller than that of TCI. [ABSTRACT FROM AUTHOR]

In this work, we aim to take a detailed experimental picture of the positive streamer. We apply optical emission spectroscopy to the first negative system (FNS, B2Σu+→X2Σg+) of N2+ and the second positive system (SPS, C3Πu → B3Πg) of N2. Large, centimeter wide, and highly reproducible streamers are created in pure nitrogen and synthetic air, at pressures ranging from 33 to 266 mbar. Direct time resolved spectral imaging of the space charge layer resulted in spatiotemporal maps of the calculated reduced electric field strength (E/N) and rovibrational temperature in sub-nanosecond and sub-millimetre resolution. The E/N peaks at approximately 540 and 480 Td, directly in front of the space charge layer, for synthetic air and pure nitrogen respectively, as determined by using the intensity ratio method of FNS and SPS. A global model for pure nitrogen in PLASIMO uses the experimentally determined E/N distribution to draw a picture of the gas kinetics around the space charge layer passage. In addition, the results of the global model serve as a reference to interpret the rotational and vibrational temperatures obtained from experimental FNS and SPS emissions.

This work presents a simplified methodology for coupling the physics of a nanosecond-pulsed discharge to the process of supersonic combustion within a backward-facing step combustor. The phenomena of plasma and supersonic combustion are simulated separately and then coupled. Based on results reported in the literature, a zero-dimensional plasma model is built, considering only the kinetic effects of the nanosecond-pulsed discharge. A set of Favre-averaged compressible Navier-Stokes equations, as well as finite rate chemistry, is used in the combustion model and solved with a control-volume based technique. The plasma-supersonic combustion coupling process only considers the discharge as a source of O and H radical species. The calculated densities of the radicals generated during each pulse from the plasma model are periodically seeded inside the domain of the combustor. The proposed methodology is used to perform a novel simulation that involved the application of plasma to a wellknown supersonic combustion experiment. The temperature and species concentration contours show that the proposed methodology captures the main effects of the nanosecond-pulsed discharge on supersonic combustion. The ignition delay time is reduced when the plasma discharge was applied. In addition, the simulations show that the plasma causes a supersonic lowenthalpy mixture to ignite, confirming the capability of the methodology. [ABSTRACT FROM AUTHOR]

Under the background of the COVID-19 pandemic, this study reports an affordable and easily prepared porous material modified by nanosecond-pulsed discharge plasma, which can adsorb SARS-CoV-2 S1 protein efficiently. Both Western blotting and an enzyme-linked immunosorbent assay were used to detect the adsorption efficiency of SARS-CoV-2 S1 protein. The physical and chemical properties of the modified porous polymer were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. We found that the new type of porous polymer material presented an excellent performance on SARS-CoV-2 S1 protein adsorption, whose adsorption efficiency reached 99.99% in 1 min. Both the physical and chemical characterizations showed that the material has many fresh pores on the material surface and that the surface is implanted with polar functional groups (C−O, C=O, O−C=O and −NH), which gives the material a high chemisorption performance along with an enhanced physical adsorption performance. Notably, the material can be prepared at prices ranging in the tens of dollars per kilogram, which shows that it could have great applications for respiratory virus protection in global epidemic states. [ABSTRACT FROM AUTHOR]

The electrical breakdown of synthetic air under ultrashort high-voltage pulses (50 ns duration), as well as slowly increasing (“DC”) voltages, is experimentally studied in a well-defined quasi-uniform electrode configuration (sphere–plane). The electrode spacing is varied from 0.1 to 1 mm, and the gas pressure is varied from 1.5 to 8 bar. The study’s goal is to provide experimental data to develop breakdown models that predict the breakdown probability of small gas gaps under arbitrary voltage excitations. In particular, this analysis is intended for applications where statistical and formative time lags need to be considered, such as nanosecond pulsed ignition or partial discharges in inverter-fed motors. The influence of the electrode material and the presence of UV illumination are investigated for both DC and pulsed voltages. The results highlight the important role of seed electron provision for breakdown under short transient voltages. Evidence for a field-assisted emission of seed electrons with a pressure-dependent onset field is found from time lag measurements. An empirical expression is derived based on the Fowler–Nordheim formula to quantify the seed electron generation rate. The expected dependence of the breakdown threshold on the cathode material (work function) was confirmed for breakdown under slowly increasing voltages (Townsend mechanism). Interestingly, a dependence of the breakdown voltage was also found for nanosecond pulsed voltages (dominated by the streamer mechanism). This suggests that the field emission of electrons from the cathode is the dominant source of seed electrons in large cathode electric fields.

This work presents a simplified methodology to couple the physics of a nanosecond pulsed discharge to the process of supersonic combustion in a flat wall combustor configuration. Plasma and supersonic combustion are separately simulated and then coupled by seeding plasma-generated radicals on the combustion domain. The plasma model is built assuming spatial uniformity and considering only the kinetic effects of the nanosecond pulsed discharge. Therefore, a zero-dimensional kinetic scheme accounting for the generation of plasma species is utilized. For the combustion model, the complete set of Favre-averaged compressible Navier Stokes equations along with finite rate chemistry is solved through a control-volume based technique via the commercial software Ansys Fluent. The computational results are compared against experimental studies showing that the proposed methodology can capture the main kinetic effects of the nanosecond pulsed discharge on supersonic combustion. OH concentration contours reveal the presence of an enhanced flame when the plasma is applied following the trends from experimental OH PLIF images. In addition, time evolving temperature and OH concentration contours show that the ignition delay time is reduced with the application of the discharge. [ABSTRACT FROM AUTHOR]

The influence of pulse rise rate and pulse duration for ignition purposes in engines is investigated. A constant volume cell is used to characterize the breakdown voltage under nanosecond pulsed voltages with automotive sparkplugs having electrode gaps ranging from 0.2 mm to 1 mm. Two pulse generators are used to compare pulses with durations of 10 ns and 50 ns. Different pulse amplitudes are used, and air gaps with breakdown voltages ranging from 4 kV to 15 kV are investigated. The cell is filled with synthetic air with densities gap distances products that are relevant for internal combustion engines. This study shows that the pulse shape and rise rate influence the breakdown voltage. Under pulsed discharge, the breakdown voltage is always above the static breakdown voltage. The probability of pulsed discharge breakdown increases as both the pulse amplitude and duration increases. Furthermore, the breakdown voltage value increases with increasing pulse rise rate. The delay time between reaching the static breakdown voltage and the actual breakdown voltage decreases with increasing overvoltage. The delay time is constituted by statistical and formative times. Both the statistical and formative times decrease with increasing overvoltage. For ignition purposes, the pulse rise rate should be as high as possible to deliver a larger energy input in the breakdown phase. Furthermore, for reduced electrode erosion, the pulse duration should be short (10-20 ns) to reduce the probability for a transition to an arc.

In this study, a magnetic field perpendicular to the electric field is introduced to the gear‐cylinder dielectric barrier discharge (DBD) to enhance the plasma density and improve the volatile organic compounds removal performance at atmospheric pressure. Higher discharge intensity, enlarged plasma streamers region, and better toluene removal performance are obtained after introducing a 0.2 T magnetic field due to the intensified ionization reactions caused by the Larmor movement of electrons. Time‐resolved Intensified Charge‐coupled Detector images indicate that both the propagation velocities of the primary and secondary streamers are enhanced and their durations are prolonged by the magnetic field. The optical emission spectra results imply that the vibrational temperature (Tvib) of N2(C‐B) and the reduced electric field (E/N) are promoted by applying the magnetic field, while the rotational temperature (Trot) of N2(C‐B) is rarely affected by the magnetic field. There is an optimal combination between the electric field and magnetic field in the gear‐cylinder DBD reactor, according to the mechanism of the magnetically assisted DBD plasma. The pulsed discharge current, toluene removal efficiency, and energy yield with the magnetic field are increased by 26%–40%, 50%–70%, and 7%–20% within the range of 16–20 kV, respectively, compared to those without the magnetic field, implying that magnetically assisted DBD plasma presents superior toluene degradation performance compared to common DBD plasma. [ABSTRACT FROM AUTHOR]

Under the background of the COVID-19 pandemic, this study reports an affordable and easily prepared porous material modified by nanosecond-pulsed discharge plasma, which can adsorb SARS-CoV-2 S1 protein efficiently. Both Western blotting and an enzyme-linked immunosorbent assay were used to detect the adsorption efficiency of SARS-CoV-2 S1 protein. The physical and chemical properties of the modified porous polymer were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. We found that the new type of porous polymer material presented an excellent performance on SARS-CoV-2 S1 protein adsorption, whose adsorption efficiency reached 99.99% in 1 min. Both the physical and chemical characterizations showed that the material has many fresh pores on the material surface and that the surface is implanted with polar functional groups (C−O, C=O, O−C=O and −NH), which gives the material a high chemisorption performance along with an enhanced physical adsorption performance. Notably, the material can be prepared at prices ranging in the tens of dollars per kilogram, which shows that it could have great applications for respiratory virus protection in global epidemic states.

Dielectric barrier discharges (DBDs) driven by nanosecond high-voltage pulses can be quite different from those driven by alternating current (ac) sources, on both electrical characteristics and plasma microparameters. In this article, the power measurement strategy in nanosecond pulsed coaxial DBDs is optimized. The effect of different experimental parameters on energy deposition and reduced electric field in plasma is investigated. First, the results measured using the instantaneous power (from the production of voltage and current) method and that using the v – q trace (Lissajous curve) method are compared and the source of divergence is analyzed. By comparing monitor capacitors with different materials and capacitances, it is demonstrated that the high-frequency response of the monitor capacitor is essential and the capacitance value can be adjusted according to the applied voltage, taking both the dynamic range of oscilloscope and the signal-to-noise ratio into consideration. Second, the influence of morphology of ground electrode, voltage rising time, and pulse width on energy deposition per-pulse and reduced electric field, obtained from the nitrogen spectral line-ratio, is studied. It is found that the copper foil promotes the discharge energy coupling per-pulse compared with the copper grid, while the reduced electric field obtained from the nitrogen line-ratio with the copper foil is weaker. A shorter rising time will also enhance the energy coupling per-pulse, as well as the reduced electric field. [ABSTRACT FROM AUTHOR]

In this paper, a nanosecond pulsed discharge was employed to modify activated carbon (AC) adsorbents for the purpose of detecting gas-phase polycyclic aromatic hydrocarbons (PAHs). The raw and modified AC were characterized by helium ion microscopy, N2 adsorption/desorption, and X-ray photoelectron spectroscopy. The treatment time, gas composition, and pulse peak voltage of discharge were optimized to improve the adsorption capacity of AC. And the adsorption kinetics of AC was investigated. It is found that the pore structure of AC is changed and the oxygen-containing groups on AC surface are increased after plasma treatment. As a result, the roles of physisorption and chemisorption are promoted, and the adsorption rate of naphthalene is improved by about 10%. More importantly, modified AC adsorbing PAHs obeys Pseudo-first-order model and Langmuir isotherm model, and the corresponding adsorption coefficients are fitted, which contributes to detecting PAHs more accurately. After modified AC enriching, the gas-phase PAHs can be detected with the limit of detections in the range of 20–120 μg/m3. [ABSTRACT FROM AUTHOR]

The present study investigates the kinetics of low-temperature pyrolysis and oxidation of n-dodecane/O 2 /N 2 mixtures in a repetitively-pulsed nanosecond discharge experimentally and numerically. Time-resolved TDLAS measurements, steady-state gas chromatography (GC) sampling, and mid-IR dual-modulation Faraday rotation spectroscopy (DM-FRS) measurements are conducted to quantify temperature as well as species formation and evolution. A plasma-assisted n-dodecane pyrolysis and oxidation kinetic model incorporating the reactions involving electronically excited species and NO x chemistry is developed and validated. The results show that a nanosecond discharge can dramatically accelerate n-dodecane pyrolysis and oxidation at low temperatures. The numerical model has a good agreement with experimental data for the major intermediate species. From the pathway analysis, electronically excited N 2 * plays an important role in n-dodecane pyrolysis and oxidation. The results also show that with addition of n-dodecane, NO concentration is reduced considerably, which suggests that there is a strong NO kinetic effect on plasma-assisted low-temperature combustion via NO-RO 2 and NO 2 -fuel radical reaction pathways. This work advances the understandings of the kinetics of plasma-assisted low-temperature fuel oxidation in N 2 /O 2 mixtures. [ABSTRACT FROM AUTHOR]

Discharges in liquids are the basis of a range of applications in electrochemistry, wastewater treatment, or plasma medicine. One advantage of discharges in water is their ability to produce radicals and molecules directly inside liquid with a high conversion efficiency. In this study, H2O2 production in a 10 ns pulsed discharge in water is investigated. The dynamic of these discharges is based on plasma ignition directly inside liquid followed by the formation of a bubble that expands in time before it eventually collapses. This sequence can be well described by cavitation theory. H2O2 is produced using different plasma conditions varying the treatment time, the pulse frequency between 1 and 100 Hz, and the applied voltage in a range from 15–30 kV. The resulting H2O2 concentration is measured using absorption spectroscopy ex situ based on a colorimetry method. The results indicate that the main parameter controlling the H2O2 production constitutes the applied voltage. The measured concentrations are compared with a global chemistry model simulating the chemistry involved during a single pulse using pressures and temperatures from the cavitation model. In addition, a global chemical equilibrium model for H2O2 creation is evaluated as well. The models show a good agreement with the data. The energy efficiency for the production of H2O2 reaches values up to 2 g/kWh. [ABSTRACT FROM AUTHOR]

Reliable and stable ignition under lean conditions is essential for safe operation of the engine. Nanosecond pulsed discharge non-equilibrium plasma assisted ignition characteristics of premixed ethylene-air flow in an advective combustion chamber were investigated. The effects of the equivalence ratio, discharge gap distance, flow velocity, discharge frequency or inter-pulse time, and pulse number were quantified in terms of ignition probability. Shadow images of ignition kernel development were captured and used to extracted the averaged kernel projected area. The results indicated that increasing the equivalence ratio, a higher flow velocity, a wider discharge gap distance, and a larger number of pulses are all conducive to the increasing of ignition probability via inducing a larger initial kernel. Increasing inter-pulse time has a non-monotonic effect on ignition probability for multiple nanosecond pulsed discharges ignition. As the inter-pulse time decreases, when neighboring kernel boundaries happen to overlap each other, the partially-coupled regime shows a higher ignition probability. Longer or shorter inter-pulse time both cause the decrease in ignition probability. The shortest inter-pulse time shown as the fully-coupled regime is the most favorable for ignition with the highest ignition probability. A method is proposed to estimate the critical frequency at which partially-coupled regime transitions to fully-coupled regime by 95% of the asymptotic time of flame development time. • The variation of ignition probability with equivalence ratio follows the sigmoid function. • Ignition probability varies non-monotonically with discharge frequency. • The lowest frequency is the optimal for partially-coupled ignition. • Discharges at critical frequency are most negative for ignition. • The critical frequency can be estimated from flame development time. [ABSTRACT FROM AUTHOR]

In this paper, an array wire-to-wire surface dielectric barrier discharge (DBD) structure is used to generate large-scale plasma by bipolar nanosecond pulse power in atmospheric air. The quantity of electrodes can be adjusted from 1 to 10 for varying discharge area. The applied voltage and discharge current are measured, the discharge images are captured, and optical emission spectra (OES) are collected. The discharge power, discharge area, and OES intensity for a single group of/and whole structure are calculated. The vibrational and rotational temperatures are simulated by the OES of N2 (C-B, $\Delta \nu =-2$), and the effects of the quantity of electrodes on discharge current, discharge power, discharge area, OES intensity, and vibrational and rotational temperatures are investigated. The results show that the discharge current has two main peaks during single applied pulse voltage, and decays in a fluctuant type. As the quantity of electrodes increases, the peak value of discharge current increases and the decaying time from peak value to zero around becomes longer. The discharge power, discharge area, and OES intensity have increasing tendencies, and those of the single group of wires decrease. In addition, when the quantity of electrodes increases, the vibrational temperature increases first and then decreases, and the rotational temperature varies in a fluctuant type. [ABSTRACT FROM AUTHOR]

• Nanosecond pulsed DBD with different parameters was applied in CH 4 dry reforming. • Discharge, conversion characteristics and emission spectrum were analyzed. • The detected maximum CH 4 &CO 2 conversions were 39.6% and 22.9%, separately. • There were higher conversion and efficiency with a shorter rise time. Dry reforming is a promising approach to converting CH 4 and CO 2 (i.e., two common greenhouse gases) into clean fuels and valuable chemicals. Non-thermal plasma, acting as an alternative to the traditional reforming processes, achieves considerable gas conversion with low energy consumption under mild operating conditions. In this study, CH 4 and CO 2 were converted to syngas (i.e., H 2 and CO) in a nanosecond pulsed dielectric barrier discharge plasma at a total gas flow rate of 50 sccm. Through evaluating the effects of electrical parameters on reforming performance, the experimental results showed that CH 4 and CO 2 conversions increased with the increase of pulse repetition frequency owing to the increased energy injection. Shorter rise and fall times resulted in better CH 4 and CO 2 conversions and higher energy conversion efficiencies, due to the rapid acceleration of electrons in a shorter discharge time. In the case where the optimal pulse peak width was 150 ns, the secondary discharge was improved because of the charge accumulation in the primary discharge, thereby increasing the CH 4 and CO 2 conversions. Among all experiments, when the pulse repetition frequency was 10 kHz and the discharge power was 55.7 W, the maximum conversions of CH 4 and CO 2 were 39.6% and 22.9%, respectively, while the total energy conversion efficiencies of the syngas and all detected products were 5.0% and 7.1%, respectively. Furthermore, an optical emission spectroscopy was used to characterize the active species formed during the reforming process. [ABSTRACT FROM AUTHOR]

The severe adverse impacts of toxic metal ions on ecosystems and human health call for the urgent development of an efficient adsorbent. In this study, a novel micro-mesoporous zeolite material was prepared by nanosecond pulsed discharge-amino co-modification method to selectively adsorb Ni(II) ions. The prepared micro-mesoporous adsorbent exhibited a large specific surface area (1042 m2 g−1) and were rich in -NH 2 and -COOH that can produce surface complexation and electrostatic adsorption with Ni(II) ions. The optimal experimental parameters were obtained at 8 min of discharge time, 16 kV of pulse peak voltage, 1 kHz of pulse repetition frequency, and pH = 7. The Ni(II) ions removal efficiency of nanosecond pulsed discharge-amino co-modified MCM-41 reached 98% within 20 min, an increase of 54% and 26% compared to the raw and solo amino modification, respectively. The adsorption processes of Ni(II) ions were well fitted by pseudo-second-order and Langmuir isotherm models, indicating that the adsorption involves monolayer chemisorption. Despite the presence of other coexisting ions, the prepared zeolites retained their excellent adsorption selectivity for Ni(II) ions. This co-modification method overcomes the drawback of mesopores blockage and further implants micropores in adsorbents, providing a novel idea and broad prospect for adsorbent modification and removal of Ni(II) ions. [Display omitted] • A novel zeolite was prepared by nanosecond pulse discharge-amino co-modification method. • Nanosecond pulse discharge modification makes up for the disadvantage of pore plugging. • The Ni(II) ions removal efficiency of prepared zeolites reaches 98%. • About 91% of Ni(II) ions removal efficiency can be reached after 7 cycles. [ABSTRACT FROM AUTHOR]

Abstract The paper proposes a simple and convenient approach to represent the discharge uniformity of nanosecond-pulse dielectric barrier discharge (DBD) in air by observation of the ratio of N 2 + (B3Σ u + → X3Σ g +, 0-0, 391.4 nm) to N 2 (C3Π u → B3Π g , 2-5, 394.3 nm) intensities. The DBDs at different pulse peak voltages, discharge gap distances, dielectric materials and thicknesses were investigated by recording their single-pulse-shot discharge images and N 2 +/N 2 ratios to verify the feasibility of the above innovative approach. The results show that the ratios of N 2 +/N 2 are in the range of 0.18–0.6within our experimental parameters, which is respect to the reduced electric field (E / N , where E is the field strength and N is gas number density) strength of 260–440 Td (1 Td = 10−17 V·cm2). And it is indicated that a lower N 2 +/N 2 ratio would be found in a higher pulse peak voltage or/and a lower discharge gap distance, which benefits for improving the discharge uniformity of nanosecond-pulse DBD. The thickness and permittivity of dielectric material also affect the E / N strength and discharge uniformity to a certain extent, but the effects are ambiguous due to additional factors of dielectric materials. In addition, the theoretical basis and application scope of this approach were also discussed. Graphical Abstract Unlabelled Image Highlights • Use a spectroscopic technique to study the nanosecond pulsed uniform DBDs in air • Reduced electric field (E/N) was estimated by the ratio of NPS and SFS intensities. • Propose the method of N 2 +/N 2 ratio to represent discharge uniformity in air DBDs • The effects of voltage, gap and dielectric on discharge uniformity were studied. • A lower E/N is in favor of the uniformity of nanosecond pulsed DBDs in air. [ABSTRACT FROM AUTHOR]

This work describes the plasma degradation process of toluene in the sliding dielectric barrier discharge (DBD) reactor based on three-electrode configuration energized by +pulse, −pulse, and ±pulse, respectively. The overall aim of this investigation is to explore the streamer propagation characteristic, spatial distribution of reactive species, and VOC degradation performance of the sliding DBD plasma under different pulsed energization conditions. The experimental result shows that the sliding DBD plasma can be ignited when the discharge electrode (electrode #1) and counter electrode (electrode #3) are energized by ±pulse (or +pulse) and −DC, respectively, while the electrode #2 is grounded. However, the sliding DBD phenomenon cannot be observed when the two air-exposed electrodes are driven by −pulse and +DC, respectively, which can be explained on the basis of different evolution mechanisms of positive and negative streamers. Optical analysis results indicate that bipolar pulse is beneficial to the ignition of DBD plasma, which can generate more reactive species compared with unipolar pulse. The toluene degradation efficiency and energy yield increase in the sequence −pulse < +pulse < ±pulse in the three-electrode DBD reactor. It is worth noting that remarkable improvements in toluene degradation efficiency, energy yield, and CO 2 selectivity can be observed for positive pulsed discharge when a three-electrode DBD reactor is employed instead of a two-electrode one, which can be attributed to the increased amount of reactive species within the entire inter-electrode distance due to sliding DBD effect. The postdischarge gas was monitored by FT-IR analysis, the main decomposition products including CO, CO 2 , H 2 O, HCOOH and discharge products such as O 3 , N 2 O, and HNO 3 can be identified regardless of the pulsed power and discharge reactor used. [ABSTRACT FROM AUTHOR]

In this work, we report on a Johnson Matthey‐developed palladium (Pd)‐based catalyst activity enhancement using nanosecond pulsed discharge treatment. The impact of treatment energy via pulse voltage, pulse frequency, and treatment time individual variation on acetylene‐to‐ethylene hydrogenation reaction performance is investigated. Up to 11.2% increase in C2H2 conversion is attained after plasma treatment at specific treatment energy of 5340 J gcat−1, while C2H4 selectivity remains constant. To elucidate the effect of plasma on catalyst activity, characterization with SEM, BET, CO chemisorption, ICP‐MS, and XRD is carried out. C2H2 conversion increase is due to the higher active metal surface area attained after the plasma treatment. Other than the improved Pd surface area, not significant increase in specific surface area is observed, while even at high energy inputs no catalyst destruction occurs, as neither metal losses, nor phase changes are induced during plasma treatment. [ABSTRACT FROM AUTHOR]

In this work, we report on low energy cost methane conversion to ethylene in a hybrid plasma-catalytic reactor system. Methane is first converted to acetylene, reaching up to 23.5% yield per pass, by a nanosecond pulsed discharge (NPD), and subsequently, acetylene is hydrogenated to ethylene using a Pd-based catalyst, which is placed in the post-plasma zone. Overall, ethylene is formed as major product at 25.7% yield per pass, consuming 1642 kJ/molC 2 H 4 , which is the lowest energy cost reported for plasma-assisted methane-to-ethylene conversion so far. The two-step process is carried out in a single reactor volume that aside from the discharge energy does not require any heat or hydrogen input since both are provided by methane cracking in the plasma zone itself. [ABSTRACT FROM AUTHOR]

In this paper, a linear shape nanosecond pulsed dielectric barrier discharge is generated at atmospheric pressure for improving the hydrophilic property of aramid fibers. The discharge images, waveforms of voltage and current, and optical emission spectra of discharge are obtained to investigate plasma characteristics, and the water contact angles, scanning electron microscopy, and X-ray photoelectron spectroscopy are employed to estimate the modifying effects of plasma and investigate modification mechanisms. It is found that 75 s is an optimal treatment time in air under 2 mm discharge gap, 28 kV pulse peak voltage, and 100 Hz pulse repetition rate, and the energy density of discharge is about 2.1 J/cm 2 . The improvement of aramid fiber hydrophilicity is due to the increasing of surface roughness and the formation of polar functional groups such as C N and O C O. Besides, the content of O 2 has an obvious influence on plasma treatment, and C C is more easily oxidized under a high O 2 concentration owing to the role of O atoms. [ABSTRACT FROM AUTHOR]

We report that gas phase plasma-assisted non-oxidative methane coupling can lead to formation of ethylene as major product at ∼20% yield per pass. This is attained by using a nanosecond pulsed discharge (NPD) reactor, featuring rapid product quenching rates, (recyclable) hydrogen co-feeding (CH 4 :H 2  = 1:1) and elevated pressures (5 bar) at which NPD is ignited. [ABSTRACT FROM AUTHOR]

The study examined the possibility of using nanosecond pulse discharges as a new ignition and assisted combustion method to solve ignition and combustion stabilization problems encountered in new combustion technologies. To better understand how temperature and the presence of radicals affect nanosecond discharge ignitions, spatiotemporal profiles of rotational and vibrational N 2 (X) temperatures were measured through spontaneous Raman scattering in a lean propane–air mixture and compared with previous results obtained in air to obtain the space- and time-resolved measurements necessary to validate the kinetic modeling of the discharge in presence of hydrocarbons. The study aims to contribute to a better understanding of the initial ignition processes in stoichiometric mixture (first observed at 1 µs) and the rapid displacement of the flame front in propane–air mixtures. In the analyzed propane–air mixture, the gas heated slightly more rapidly than in air. This temperature increase might have occurred in the release of energy resulting from dissociation of propane due to quenching by metastable species. The presence of traces of CO confirmed this assumption. The energy transfer processes were identical in all other respects and occurred over the same time scales in air and in the propane–air mixture. Once the flame in the stoichiometric mixture was ignited, it propagated through a cylindrical channel whose diameter was identical to that of the volume of gas heated to above 900 K in the lean propane–air mixture. This early ignition and the spreading of the flame kernel demonstrate the combined effect of radicals and temperature on the nanosecond discharge ignition process. The resulting new database makes it possible to validate simulations of the vibrational kinetics involved in nanosecond discharges of a lean propane–air mixture and provides a first step toward modeling flame initiation. [ABSTRACT FROM AUTHOR]

Complexity of branching pattern and OH production of water surface discharges was investigated by comparing nanosecond water surface discharge (NWSD) and microsecond water surface discharges (MWSDs) that were defined as NWSD and MWSD, respectively. Experimental and analyzed results between NWSD and MWSD under comparable maximum discharge length ld are summarized as follows: 1) NWSD showed the greatest complexity of branching pattern by fractal analysis; 2) electron density of NWSD was approximately two times greater than MWSD and both orders were 10−17 cm−3; 3) emission intensity of OH (A-X) from MWSD was greater than NWSD; 4) rotational temperature of NWSD was almost constant around 1000 K irrespective of ld and rotational temperature of MWSD increased with increasing ld ranging from 2000 to 4000 K. It was found that the complexity of discharge pattern on water may be affected by the field intensity at water/air boundary. OH production was presumed to be caused by thermal dissociation in this experimental condition. [ABSTRACT FROM PUBLISHER]

This paper reports on the dependence of voltage rise rate on positive streamer branching and shock waves in supercritical carbon dioxide. Voltages with rise rates of 0.21 and 4.5 kV/ns were applied to a needle-to-plane electrode. Prebreakdown phenomena involving streamer growth and shock wave propagation were observed by means of a shadowgraph method. The results show that the spread angle of the streamer at the needle tip under 4.5 kV/ns was nearly twice as large as that under 0.21 kV/ns. The discharge may initiate without density reduction due to electrostrictive force. While shock wave Mach number was little affected by the voltage rise rate, it increased by increasing the negative voltage peak. Consequently, the velocity of shock wave is presumed to be influenced by the population of the vibrational state of carbon dioxide. [ABSTRACT FROM PUBLISHER]

This article presents a brief selective overview of current trends in plasma-assisted ignition for internal combustion engines. Short duration pulsed nonequilbrium plasmas show promise for improved engine performance, including extension of the lean limit, reduction of NOX, and consistent cycle-to-cycle ignition timing. This article presents methods for achieving these improvements, including the use of lasers, microwaves, and high voltage nanosecond pulse driven discharges. These approaches can provide multiple simultaneous ignition points, optimized localization of ignition within the combustion chamber, and precise timing. A classification of nonequlibrium pulse driven ignition systems from the physical point of view and a discussion of different breakdown mechanisms are included, along with a discussion of recent laboratory and road test results. [ABSTRACT FROM AUTHOR]

In this paper, an atmospheric surface barrier discharge (SBD) generated by annular electrodes in quartz tube is presented through employing bipolar nanosecond pulse voltage in air. The discharge images, waveforms of pulse voltage and discharge current, and optical emission spectra emitted from the discharges are recorded and calculated. A spectra simulation method is developed to separate the overlap of the secondary diffraction spectra which are produced by grating in monochromator, and N 2 (B 3 Π g → A 3 Σ u + ) and O (3p 5 P → 3s 5 S 2 o ) are extracted. The effects of pulse voltage and discharge power on the emission intensities of OH (A 2 Σ + → X 2 П i ), N 2 + (B 2 Σ u + → X 2 Σ g + ), N 2 (C 3 Π u → B 3 Π g ), N 2 (B 3 Π g → A 3 Σ u + ), and O (3p 5 P → 3s 5 S 2 o ) are investigated. It is found that increasing the pulse peak voltage can lead to an easier formation of N 2 + (B 2 Σ u + ) than that of N 2 (C 3 Π u ). Additionally, vibrational and rotational temperatures of the plasma are determined by comparing the experimental and simulated spectra of N 2 + (B 2 Σ u + → X 2 Σ g + ), and the results show that the vibrational and rotational temperatures are 3250 ± 20 K and 350 ± 5 K under the pulse peak voltage of 28 kV, respectively. [ABSTRACT FROM AUTHOR]

The impact of three cold atmospheric plasma (CAP) sources, atmospheric pressure plasma jet (APPJ), two- dimension dielectric barrier discharge (2D-DBD), and nanosecond pulsed discharge (ns-pulsed) on the structure, functionality, and amino acid composition of pea protein was evaluated. Different plasma sources and associated reactive species resulted in protein denaturation, increased surface hydrophobicity, formation of soluble aggregates mostly by disulfide linkages, and changes in secondary structures. Enhancement in surface properties, presence of soluble aggregates, and increase in β-sheet contributed to significant improvement in gelation and emulsification. Enhanced emulsion stability was attributed to relatively small droplet sizes and high surface-charge. Differences among CAP-treated samples were attributed to differences in fluence and composition of plasma-produced reactive species. While all three plasma treatments could be appreciable functionalization approaches, 2D-DBD (Ar + O 2) treatment for 30 min had insignificant effect on the amino acid composition. [Display omitted] • The impact of three cold atmospheric plasma sources on pea protein was elucidated. • The fluence and composition of reactive species caused protein structural changes. • Surface properties, aggregates, and β-sheet changes caused functional enhancement. • All three CAP treatments proved to be appreciable functionalization approaches. • 2D-DBD treatment had the least impact on amino acid composition. [ABSTRACT FROM AUTHOR]

NPDBD plasma actuation is a novel method for active flow control. In Benard's paper, compression waves induced by NPDBD plasma actuation with shorter rise time are stronger. But the mechanism is still not clear yet. In this paper, NPDBD plasma actuation with different rise times are simulated using a two-dimensional plasma-fluid coupled model. Along with the decrease of rise time from 150 ns to 50 ns, discharge current, peak power, and input energy increase with constant voltage amplitude. The whole ultrafast heating energy and heating efficiency also increase, while the ratio of quenching heating and ion-neutral collision heating remains almost unchanged. Due to higher heating energy, the strength of the induced compression wave also increases with the shorter rise time. The variation law of discharge current and compression wave strength is consistent with the trends observed in Benard's paper. The main mechanism for higher ultrafast heating energy and efficiency with shorter rise time is that both maximum reduced electric field and electron density are higher. Evolution of reduced electric field, electron density, heating distribution, and induced compression wave are also presented. [ABSTRACT FROM AUTHOR]

Atmospheric pressure low-temperature plasma can directly oxidize and fix nitrogen from the air, offering advantages such as mild reaction conditions, flexible and controllable parameters, and avoiding greenhouse gas emissions. In this paper, a nitrogen fixation study was carried out by using a double needle-plate electrode to form a bubble discharge plasma in water, with air as the discharge gas. The influencing factors of product concentration and energy consumption in the nitrogen fixation process were analyzed. The results show that the plasma contains varied active species such as nitrogen atoms, oxygen atoms, hydrogen atoms, and excited state nitrogen molecules, enabling efficient synthesis of nitric nitrogenous products. It is found that the pulse parameters, electrode gap, and working gas components have an important influence on the nitrogen fixation performance of the bubble discharge plasma. The highest NO-x synthesis rate of the device is 19.2 μmol/min, corresponding to a minimum energy consumption of 11 MJ/mol. The optimal nitrogen fixation performance is observed at an electrode gap of 6 mm. Addition of an appropriate amount of oxygen in the air（with the ratio of oxygen/nitrogen of 0.4） can enhance the product synthesis and reduce the energy consumption. [ABSTRACT FROM AUTHOR]

A new design of the compact nanosecond pulse generator based of the drift step recovery diodes as an ignition system for internal combustion engines (ICEs) has been presented. Experimental results of the comparative analysis of the standard ignition system and an ignition system on the basis of the nanosecond pulsed discharge for the four-cylinder ICE have been presented. It was shown that a nonequilibrium plasma formed by the discharge was an effective way to reduce the specific fuel consumption as well as the concentration of nitrogen oxides in the engine exhaust gases. A numerical analysis of possible mechanisms of the nonequilibrium plasma influence on the suppression of the nitrogen oxides formation has been carried out. [ABSTRACT FROM PUBLISHER]

In the use of spark gaps as switching devices in pulsed power systems, spark resistance is a crucial factor influencing the voltage rise time and the efficiency of energy delivered to the load. However, current oscillations make it difficult to accurately measure the spark resistance. Therefore, we present a spectrographic method to measure the spark radius and the conductivity of spark channel according to its emission spectrums. A series of experiments has been carried out to investigate the time-dependent properties of spark resistance under oscillatory damped current pulses. The current and voltage waveforms have been recorded to calculate the energy deposited in the spark channel. Furthermore, the influences of gas pressure and gap length on spark resistance and the deposited energy have been discussed. The results indicate that lower resistance, and energy deposition is obtained with shorter gap lengths operating at higher pressures. [ABSTRACT FROM PUBLISHER]