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Deposition of transparent oxide films at atmosphere pressure onto polymeric substrates at room temperature is a technique gaining rapid acceptance. These films can be used for numerous applications such as antiscratch and water permeation barrier coatings. In this paper, a \sim 1.4 - \mu \text{m} SiOx layer has been deposited on polypropylene-coated paper at atmosphere pressure with a filamentary dielectric barrier discharge (DBD). The DBD linear discharge was driven by a 30-kHz power supply. Scanning electron microscope, X-ray photoelectron spectroscopy, and attenuated total reflection-Fourier transform infrared spectroscopy were used to characterize the deposited film. The deposited thin film decreased water permeation through the paper by \sim 15$ %. [ABSTRACT FROM PUBLISHER]

To enhance the heat dissipation of high-power light-emitting diodes (LEDs), corona wind based on corona discharge was promoted. In this paper, we aimed at reinforcing the intensity of corona wind by modifying the needle electrode with graphene solution. To explore the differences in the graphene-coated electrode and the original bare electrode on the electrical characteristics, the intensity of corona wind, and LED heat dissipation, a corona wind cooling system and a thermal test system were built for the experimental study. The results showed that the graphene-coated electrode system could produce corona wind at a lower voltage. In addition, the discharge current of the graphene-coated electrode system is higher than that of the bare electrode system under the same discharge voltage. The graphene-coated electrode system can induce a faster corona wind and the highest speed is about 3.4 m/s, showing that it is more efficient than the bare electrode system in corona wind production. Moreover, the temperature drop of LEDs for the graphene-coated system is greater, which means that the corona wind cooling system can reduce the junction temperature of the LED chips effectively. Ultimately, as the discharge power increases, the average convective heat transfer coefficient increases. Indeed, the result of this paper can be used for the wide variety of the graphene-coated corona wind generator application as a promising technology for the LED heat management. [ABSTRACT FROM AUTHOR]

The interest in the use of atmospheric-pressure plasma jets (APPJs) is constantly growing. APPJs offer various ranges for applications, such as wound healing, cancer treatment, and dental care. The complex plasma chemistry plays an important role in each of these fields but is often poorly understood. In this paper, the production of atomic oxygen in a radio frequency helium–oxygen plasma is investigated by means of a numerical simulation. A 1-D discharge of an atmospheric-pressure plasma jet is created with the plasma module of COMSOL Multiphysics, using a set of 25 reactions. Many 1-D simulations usually cannot estimate the power deposition in a correct way because of suspected arising losses, such as radiation and inefficiencies of the external circuit. In order to match the experimental power deposition of 13 W, high voltages (855 V) are required in the model. Such high voltages cause changes in the plasma characteristics like a switch in the glow mode. The impact of the voltage on the plasma is investigated by the comparison of a low-voltage (325 V) simulation, which matches the experimental oxygen production, and a high-voltage (855 V) simulation, which matches the experimental power deposition. Outcomes of this paper further support the idea that the power deposition measured in experiments is higher than the actual power deposition coupled to the plasma. [ABSTRACT FROM AUTHOR]

This paper embodies the results of experimental studies of a dielectric barrier discharge low-temperature nonequilibrium plasma reactor that runs in air and nitrogen at atmospheric-pressure conceived for surface treatment applications. A homemade reactor, of typical plane-to-plane geometry with the dielectric covering the upper electrode which is stressed by a high voltage (40 kV, 3–20 kHz) is used. Electrical signals (current and voltage), optical emission spectroscopy records, and total light emission measured by photomultiplier have been analyzed and used to distinguish different plasma regimes which are studied for the treatment of a lignocellulosic material (sugarcane bagasse). In the filamentary discharge regime, the gas temperature of few tens of degree Celsius above the ambient one was determined, the electronic temperature of some electronvolts and electron density in the range of 1012–1013 cm−3 were estimated. Plasma treated pellets of sugarcane bagasse were analyzed by diffuse reflectance infrared Fourier transform spectrometry and the relative results obtained under filamentary discharge regime have shown significant degradation of the lignin macromolecule. It has been shown important modifications on the lignocellulosic material, namely, the plasma attacks drastically the lignin bonds. Strong modification of lignin was observed near wavenumber of 3400 cm−1, due to stretching vibrations of OH, and for the band 1114 cm−1 which is related to C=C and C=O stretching. Severe decrease of the band intensity 1596 cm−1, which due to C=C stretching and C=O, is also a result of the treatments done in this paper. [ABSTRACT FROM AUTHOR]

In this paper, a complete flux scheme (CFS) has been implemented in 1-D fluid model for simulating the pulsed dielectric barrier discharge (DBD) in pure argon at atmospheric pressure. The characteristic quantities of the pulsed DBD have been systematically calculated by using the CFS and presented in comparison with those by using the exponential difference scheme (EDS). This paper shows the following results. There is the two-pulse discharge mode in the present simulation. The two discharge currents obtained using the CFS and EDS converge to the same result in good agreement with the experiment as spatial step length decreases, but the CFS has a fast convergence performance compared to the EDS. With a small grid number, the numerical scheme has an evident effect on the characteristic quantities in the time region corresponding to the first discharge pulse. This paper suggests that in the pulsed DBD, the usage of the CFS with a properly small grid number can give more accurate result and also presents a high calculation efficiency. [ABSTRACT FROM AUTHOR]

In this paper, atmospheric-pressure air and oxygen corona plasma jets under water surface have been used to generate plasma-activated water (PAW) to inactivate colletotrichum gloeosporioides (C. gloeosporioides) suspension. The atmospheric-pressure plasma jets in the water were characterized by measuring: 1) the electrical and optical properties for evaluating the plasma efficiency and 2) the physicochemical properties of PAW, including pH value, oxidation-reduction potential value, and the concentration of hydrogen peroxide, nitrite, and ozone. The aim of this paper is to investigate the effects of long-lived reactive oxygen and nitrogen species (RONS) and environmental factor (acidity) in PAW on fungicidal property. The results of antifungal activity show that the inactivation rate of C. gloeosporioides is higher using air-PAW than oxygen-PAW, and increases with increasing reaction time when preparation time of PAW is fixed as 30 min. This correlates well with measurements of the aqueous-phase long-lived RONS concentration such as nitrate and ozone, suggesting these species play crucial roles in the inactivation process. [ABSTRACT FROM AUTHOR]

In this paper, an investigation of the control of electron energy in the atmospheric-pressure helium plasma jet produced by a needle–plane discharge system has been performed by means of the numerical simulation based on a 2-D self-consistent fluid model. Due to the consideration of practical application of the cold atmospheric-pressure plasma jet (CAPPJ) in the fields of biomedicine, in this paper, the mean electron energy (MEE) nearby the cathode plane is accounted for. The parameter dependences of the MEE have been systematically calculated. The considered parameters include the voltage amplitude and rising time $t_{r}$ of the applied voltage pulse as well as needle electrode radius. The voltage amplitude is changed in the range from 3 to 19 kV, and $t_{r}$ is from 1 to 200 ns. The spatial electric field has also been analyzed in detail because of its dominant role in controlling electron energy. In addition, the effect of electron energy on the production of the reactive species OH, O3, and H2O2 has also been investigated when considering the addition of humid air to the working gas helium. This paper gives the following significant results. For a given $t_{r}$ , the MEE increases almost linearly with increasing voltage amplitude. The effect of voltage amplitude on the MEE becomes much more evident for smaller $t_{r}$ and is obviously weak for the $t_{r}$ with a few hundreds of nanoseconds. Fixing the voltage amplitude, the MEE decreases with the increase in $t_{r}$. The dependence of the MEE on $t_{r}$ is evident for a high voltage amplitude and the reverse is true for the lower voltage amplitudes. As a whole, the higher voltage amplitude and smaller rising time $t_{r}$ or their synergism should be considered for obtaining high electron energy. Especially, an MEE of about 10 eV can be obtained, which covers the energy thresholds inducing all the processes of dissociative electron attachment to water molecule and thus is of essential importance for the production of the reactive species such as OH, H2O2, and O3 in the interactions of plasmas with the aqueous solution embedded in biofilms or tissues. The needle electrodes with different radii result in a minor variation of the MEE under the fixed voltage amplitude and $t_{r}$. Therefore, changing the radius of the needle electrode is not an effective solution to the control of electron energy in the CAPPJ. Furthermore, the parameter dependence of the spatial electric field is similar to that of the MEE, which reveals the dominant role played by the spatial electric field in controlling electron energy in CAPPJs. Considering the addition of humid air to the working gas helium, with the increase in electron energy, the averaged densities of OH and O3 increase, but that of H2O2 decreases. [ABSTRACT FROM AUTHOR]

The study on breakdown characteristics at microscale is very vital to the plasma physics community and micro/nanoelectronic industries. However, the dynamic development processes including the electron avalanche and discharge channel during the breakdown event are still unclear experimentally so far due to the restriction of the in-situ diagnostic technique. In this paper, an optical diagnostic technique is put forward to achieve an in-situ observation of the dynamic breakdown process across microgaps at atmospheric pressure. By using the nanosecond temporally and micron spatially resolved optical measurement method, the light emission appearances of microgap breakdown under nanosecond pulse have been captured and imaged directly. The initial and propagation mechanisms for electrical breakdown across the very small air gap are discussed based on the light emission properties. Results show that the light emission initiates from the cathode as the initial electron avalanche, then the avalanche transits to the streamer due to the space charge effect and photoionization, and propagates towards the anode with a velocity of 4.40×103 m/s, demonstrating a cathodedirected streamer in the pulsed breakdown. The space charge induced field enhancement and photoionization are proved to play a significant role in the pulsed breakdown across microgaps. In addition, the time to breakdown is estimated to be about 20ns while the formative time lag is about 9ns through the temporal sequence of the optical images. The in-situ optical measurement technique presented in this paper would be of a great help for better understanding the physical mechanism of microgap breakdown. [ABSTRACT FROM AUTHOR]

In this paper, the effects of aluminum nitride and alumina ceramics on the discharge mode of He/O2 mixed gas are studied and compared. It is found that when the O2 volume fraction is in the range of 0.2%–1%, dielectric barrier discharge (DBD) with Al2O3 is always in the unstable filamentary mode, and homogeneous and filamentary modes are observed in DBD with AlN. Under the homogeneous discharge mode, there is only one current pulse each half-voltage cycle, and the intensified charge-coupled device discharge image shows that it is glow discharge. The relative permittivity and surface charge decay characteristics of AlN and Al2O3 are measured. The experimental results show that the relative permittivity of AlN is lower than that of Al2O3, but its surface charge decay is obviously slower than that of Al2O3. The derived electron trap density from the surface charge decay of AlN ceramic is higher than that of Al2O3, which shows AlN has a strong charge capacity and can emit more electrons in the second half cycle of the discharge. The higher secondary electron emission coefficient can make the discharge ignition voltage lower and the formation of stable homogeneous discharge easier. This paper provides a new control method for expanding homogeneous discharge in He/O2 mixed gas. [ABSTRACT FROM AUTHOR]

Multilayer dielectric barrier discharge (DBD) can efficiently enlarge the volume of homogeneous plasma and its interactional surface area with materials in vertical space, which seems attractive to the industry application. In this paper, a new plasma generator of DBD structure which has multilayers of dielectric barrier boards excited by repetitive submicrosecond pulsed power (0 to -100 kV, 130 Hz-1 kHz, pulsewidth 230 ns, and rise time 120 ns) is introduced, and homogeneous plasma has been obtained in atmospheric pressure air. Experiments on high-speed photography with an exposure time of 5 ns have been carried out to the discharge with three layers of dielectric barrier boards with each gap width of 2 mm. It demonstrates that luminance of the discharge distributes uniformly throughout the upper and the lower gaps. Also, the result of the time evolution image of a three-layer DBD is discussed in this paper, which shows that the two layers of luminous intensity keep good consistency with each other, and this indicates that breakdown of each gap layer happens at the same time in a multilayer DBD. A preliminary processing experiment for polytetrafluoroethylene film has been carried out by adopting homogeneous triplelayer DBD plasma. By testing the water contact angle of the polymer surface before and after the treatment, it was found that hydrophilism of the surface and efficiency of treatment could be effectively improved by the processing of each layer of discharge plasma. [ABSTRACT FROM AUTHOR]

This paper describes the time evolution of ball plasmoids generated by millisecond atmospheric discharge in contact with water. The aim of this paper was to clarify an initiation and a formation mechanism of an atmospheric ball plasmoid. The use of a higher frame rate of filming and shorter exposition time, in comparison with past experiments, allows us to observe the fast processes that occur during a plasmoid evolution. We assert that an initial electrical breakdown in a cathode ceramic tube filled by a conductive liquid is essential for further plasmoid formation. It generates a shock wave resulting in a blast of conductive liquid. The resulting expansion of water vapor and bubbles with an addition of weekly ionized plasma serves as a main source of matter for plasmoid formation. We also note that an electrical arc generated after the breakdown transforms to a plasma jet. This jet accelerates plasma to the plasmoid. [ABSTRACT FROM AUTHOR]

DC winding induced voltage pulsation in wound field switched flux (WFSF) machines causes dc winding current ripple and field excitation fluctuation, challenges the dc power source, and deteriorates the control performance. Hence, reducing this pulsation is important in the design of a WFSF machine. In this paper, based on the analytical models, rotor skewing and rotor iron piece pairing are proposed and comparatively investigated by the finite-element (FE) method to reduce the on-load dc winding induced voltage in WFSF machines having partitioned stators and concentrated ac windings. FE results show that peak-to-peak value of the on-load dc winding induced voltage in the analyzed 12/10-pole partitioned stator WFSF (PS-WFSF) machines can be reduced by 78.42% or 77.16% by using rotor skewing or rotor pairing, respectively, while the torque density can be maintained by >90%. As for the 12/11-, 12/13-, and 12/14-pole PS-WFSF machines, by using rotor iron piece inner arc pairing, the on-load dc winding induced voltage can be reduced by 64.11%, 52.12%, and 76.49%, respectively, while the torque density can be maintained by more than 90%. Prototypes are built and tested to verify the analytical and FE results. [ABSTRACT FROM AUTHOR]

Atmospheric pressure plasma jets (APPJs) have attracted considerable interests due to their low-temperature and easily controlled features. In order to cover a larger area for broader applications, spatially extended atmospheric plasma arrays are designed and constructed by a number of packed plasma jets. Despite their outstanding stability and flexibility, it remains a challenge for the jets to form large-scale uniformity on downstream substrates due to complex electrical and hydrodynamic interactions. In this paper, we use a 2-D temporally evolving code coupling electric, flow, and temperature fields, as well as chemical reactions to study synergistic effects of the multi-fields coupling on discharge and propagation characteristics of the jet array based on a USim software framework. The influence of gas flow and a substrate downstream on the plasma jets dynamics and uniformity are investigated by the model. Also, essential strategies for uniformity modulation are acquired. Results show that the balanced evolution of the ionization process and the effective merging of discharge channels could be realized by modulating the gas flow field. Therefore, a homogeneous distribution of plasma downstream can be obtained by adjusting the gas flow field properly, which provides a new efficient way for the uniformity control in the field of plasma processing. [ABSTRACT FROM AUTHOR]

Chemical oxidation and the bactericidal capabilities of nonthermal plasma discharges can be used in different practical applications, such as biodecontamination, sterilisation of medical equipment, waste water treatment, syn-gas treatment, and others. In this paper, the oxidation and biodecontamination effects of impulsive plasma discharge, which propagate across a liquid sample/air interface (surface discharges), and through the bulk of a liquid sample (direct discharges), have been investigated. The oxidizing capability was analyzed by measuring the degree of decolorization of indigo carmine dye in water solutions. Gram-negative and gram-positive bacterias, E. coli and S. aureus, respectively, were used as model microorganisms in the investigation of the biocidal effects of plasma discharges. Surface and direct plasma discharges were generated by high-voltage impulses of both polarities, with the magnitudes of 20, 24, and 28 kV, and the chemical oxidation and biodecontamination capabilities of such discharges have been obtained and analyzed. It has been established that the defining factor in the chemical and biological effects of plasma discharges is the normalized delivered charge (dose). The results obtained in this paper show that surface discharges have greater biodecontamination capability as compared with direct transient plasma discharges. Also, it was shown that the decontamination rate of E. coli is more than double than that of S. aureus. [ABSTRACT FROM AUTHOR]

In this paper, we characterize a Transparent Cathode Discharge (TCD), a type of Inertial Electrostatic Confinement (IEC) plasma, operated in helium and argon in the pressure range of 1–100 Pa. The discharge was investigated using a combination of electrical and optical diagnostic techniques. The imaging of the discharge indicated distinct operating regimes related to the background gas pressure, with each mode being characterized by different patterns of optical emission. The spectroscopic analysis of the optical emission showed that this mode structure represented an electron-driven discharge at higher pressures, and a discharge sustained by the activity of energetic heavy particles at lower pressures. The high-pressure discharge is shown to be assisted by the hollow cathode effect toward its low-pressure limit, and the visible color of emission from the discharge in helium is found to provide a convenient diagnosis of active species. The identification of a stable discharge mode in which energetic heavy particles are responsible for collisional processes has the potential to lead to new industrial applications based on this novel heavy particle-driven reactive plasma source. [ABSTRACT FROM AUTHOR]

The authors have carried out measurement of the current waveforms associated with lightning discharges to wind turbines near the coast of the Sea of Japan in Tohoku. In this paper, measured waveforms in winter from 2013 to 2018 are investigated and the charge transfer of lightning flash initiated by upward propagating leaders is studied. The charge transfer associated with bipolar lightning is higher than that associated with unipolar lightning. The lightning charge transfer of the typical winter atmospheric pressure pattern thunderstorms (TWPs) with relatively low −10 °C isotherm altitude is less than that of OTT (other thunderstorms than the TWP) at Nikaho and in Tohoku. In Hokuriku, another winter lightning area, the charge transfer of the lightning flash is almost the same regardless of the above-mentioned two types of the thunderstorms as well as the −10 °C isotherm altitude. As the result, it is pointed out that the charge transfer is dependent on the −10 °C isotherm altitude and types of thunderstorms, and that characteristics of winter lightning depend on the region. It is commonly found that the charge transfer exceeding 300 C occurs when the altitude of −10 °C isotherm is between 1000 and 2500 m above the sea level. [ABSTRACT FROM AUTHOR]

The dielectric-barrier discharges (DBDs) under airflow have been widely used in the fields of airflow control, plasma-assisted combustion, and surface modification. Our previous work demonstrates that the discharge intensity under airflows could be adjusted by a discharge configuration with upstream and downstream electrodes. In this paper, a further investigation of discharges under airflows is processed with a multicathode DBD configuration. With the injection of airflows to the discharge region, the first upstream region produces a decrement of discharge intensity, while the following downstream region always provides greater discharge intensity than that of the adjacent upstream discharge region. An optimal discharge configuration is found by appropriately selecting the distances between the cathodes, wherein the last downstream region can produce maximum discharge intensity. The mechanisms are analyzed by considering the transport effect of airflows and the lifetime of charged and metastable particles. The charged and metastable particles are transported to the downstream region, and these particles always act as the responsible seeds to enhance the downstream discharges. In addition, due to the limited lifetime of charged and metastable particles, the enhancement effect may be weakened under long transport distances. Finally, potential applications for multicathode DBDs are also provided. [ABSTRACT FROM AUTHOR]

Modeling of the packaged wind sensor operating on constant power (CP) mode is proposed in this paper. The proposed model is based on the theory of heat conduction and forced convection. The presented model indicates that the total output dc voltage is proportional to the square root of the wind speed, and ${V}_{x}$ , as well as ${V}_{y}$ , varies with the wind direction based on cosine function. The wind sensor is fabricated by microelectromechanical systems (MEMS) technology and packaged with the glue. The test is performed in the wind tunnel and the measured results indicate an agreement with the presented model. The relative error of voltage for the wind speed is less than 14% up to 30 m/s, while that for the wind direction is no more than 10.7% from 0° to 360°. [ABSTRACT FROM AUTHOR]

This paper presents the GaxZn1−xO (x = 0, 0.1, and 0.3)-based photodetectors (PDs) by using mist atmospheric pressure chemical vapor deposition. X-ray diffraction and X-ray photoelectron spectroscopy are used to characterize crystal orientation, chemical qualitative, and quantitative characteristics of the GaxZn1−x (x = 0, 0.1, and 0.3) thin films. The photoluminescence is used to observe the near-band-edge emission and trap energy level. Among these three PDs, the Ga0.3Zn0.7O-based PD shows the lowest dark current, smallest noise current, and shortest response time. Furthermore, the Ga0.3Zn0.7O-based PD exhibits higher UV-B to UV-A rejection ratio and higher UV-B to visible rejection ratio. It is found that the cutoff wavelength is tunable by changing Ga contents in GaxZn1−x thin films. [ABSTRACT FROM AUTHOR]

In this paper, the dual-frequency atmospheric-pressure glow discharge is operated in helium with a small amount of oxygen. It is found that the plasma density increases, but the reactive atomic oxygen density decreases with high-frequency (HF) power. The plasma density also increases with low-frequency (LF) power, but it is weak as with HF power. However, the reactive atomic oxygen density increases with LF power. It shows that HF power is in favor of excited helium, but LF power is in favor of producing reactive O, N2, and OH. The discharge intensity decreases with oxygen gas admixture in working gas due to its electronegative nature. The generation rate of reactive oxygen atom has a trend of increasing first and then decreasing after 0.3% oxygen gas admixture. [ABSTRACT FROM AUTHOR]

The characterization of an atmospheric pressure microwave argon plasma in the form of a plasma sheet and the results of its use in the investigation of the wettability modification of polyethylene (PE) surfaces are presented in this paper. The spectroscopic investigations performed indicate a plasma temperature at the level of 750–1100 K and an electron density at the level of 2.9– $5.4\times 10^{14}$ cm−3. The following PE-type specially prepared materials were subjected to the plasma treatment process: PE (pure low-density PE), PE + UV (PE with a UV stabilizer), PE − UV + M (with a UV stabilizer and a montmorillonite), PE + S (PE with soot), and PE − F (PE with a UV stabilizer, a montmorillonite, and soot). The experimental investigations prove the high potential of the presented method for the PE surface activation in industrial applications. The atomic force microscopy scanning of samples was performed before and after the plasma treatment. The aging of the adhesion enhancement effect indicates that the water contact angle is related to the surface energy changes. [ABSTRACT FROM AUTHOR]

In our previous study, internal stress was suggested as the mechanism causing the deterioration of paint adhesion through atmospheric-pressure plasma irradiation. In this paper, this mechanism is examined in detail. According to the Japanese Industrial Standards (K-5600-5-7), we evaluate the experimental results by varying some parameters. An applied voltage of 10 kV, plasma irradiation distance of 10 mm, and plasma irradiation duration of 60 s are the parameters that resulted in the peeling of the paint at a lower peeling-off load. In addition, from the simulation results, the generation and thermal input of a plasma streamer are confirmed and considered as one of the factors causing the paint to peel more readily. [ABSTRACT FROM AUTHOR]

In this paper, the evolution and transition mechanisms of typical nonlinear phenomena in an atmospheric pressure helium dielectric barrier discharge (DBD) are investigated from the perspective of transient evolution properties through fluid modeling. By gradually up-regulating the interelectrode gap width, the discharge (steady state) evolves from symmetric single-period (SP1), through asymmetric single-period (AP1), into Period-2 (P2) state. Similar evolution trace can also be obtained when increasing the driving frequency. Right after the initial breakdown, the discharge goes through several transient periods featuring unstable asymmetric current pulses before the establishment of steady-state discharge. As the bifurcation parameter increases in excess of the critical value, the discrepancy between the seed electron level of positive and negative discharges accumulates over the transient periods, switching the discharge into AP1 state. After then, a further elevation in the gas gap width (or driving frequency) leads to the generation of a “moderate intensity” positive pulse. With the “moderate intensity” positive pulse and a stronger positive pulse emerging alternatively in the temporal waveform sequence, the discharge evolves into P2 state. Finally, based on the transient evolution mechanisms, a preliminary state-controlling method regarding the use of a first-peak-leveled applied voltage is proposed, which may shed light on the modification of nonlinear states in some practical DBD application scenarios. [ABSTRACT FROM AUTHOR]

Gas flow plays an important role in determining the discharge properties in microwave plasma torches sustained by the propagating surface wave. This paper aims to investigate the gas flow effects on the plasma column length, the surface wave propagation, and the heavy species temperature in a surface wave plasma torch operated at atmospheric pressure. The steady-state discharges of pure argon gas at atmospheric pressure under different gas inflow rates in the plasma torch are characterized by an improved 2-D axisymmetric fluid model. The obtained results demonstrate that increasing the gas inflow rate is able to decrease the surface wave propagation distance, accelerating the contraction of the plasma column length. The discharge instability is found to be motivated by the disappearance of the sustaining surface wave at high gas inflow rates. Besides, a temperature drop of about 64 °C is observed at the temperature-maximum point of the glass tube with an increase in the gas inflow rate from 1 to $16\,\,\text {L}\cdot \text {min}^{-1}$. Therefore, for the surface wave plasma torch operated with only the axial gas flow, increasing the gas inflow rate cannot solve the glass overheating problem. [ABSTRACT FROM AUTHOR]

When the pressure and temperature of a fluid exceed a critical point, the fluid enters into the supercritical (SC) region. In this region, the physical properties are believed to be in favor of a good current interruption medium. This paper focuses on the arc voltage characteristics of nitrogen arcs burning inside cylindrical tubes at different filling pressures: 1, 20, 40, and 80 bar, thus covering the SC region. Two different tube materials have been used in the experiments, alumina and polytetrafluoroethylene. Arc voltages are measured for arcs burning inside tubes of 2, 4, 8, and 15 mm inner diameters. In addition, free-burning arcs have been investigated at the same filling pressures. The arc current was 150 A at 350 Hz throughout the study. The arc voltage is found to increase with decreasing inner diameter of the tube at atmospheric pressure. At higher filling pressures (i.e., 20, 40, and 80 bar), however, such a simple relationship is not observed. The arc temperature and radius have been calculated based on the “simple theory of free-burning arcs” and the “two-zone ablation arc model.” The calculated arc radius decreases with increasing gas pressure. Furthermore, due to increased absorption of radiation at high filling pressures, ablation is found less significant for ultrahigh-pressure nitrogen arcs compared to atmospheric pressure arcs. This is in line with the observations from optical micrographs of the inner surfaces of the tubes exposed to arcs at different filling pressures. [ABSTRACT FROM AUTHOR]

The properties of corona discharge in practical applications are strongly influenced by the variation of environmental parameters. A 2-D axisymmetric hydrodynamic drift–diffusion model coupled with Poisson’s equation and three Helmholtz differential equations is established to investigate the effect of environmental temperature on negative corona discharge under the action of photoionization. This numerical model is performed by a traditional needle-to-plane configuration in dry air at atmospheric pressure. The characteristics of Trichel pulses, negative ion density, electric field, and electron density are discussed in this paper. It is found that the magnitude of Trichel pulses, first pulse duration, and pulse frequency increase with increasing the ambient temperature. Moreover, the effect of photoionization under these conditions is also investigated by simulations intensively. [ABSTRACT FROM AUTHOR]

To realize the broadest potential of nonthermal atmospheric-pressure plasma (APP) technology, there is a need to develop low-cost, compact devices that can be used for portable applications. One of the greatest impediments to this is the power supplies and/or electronics needed to generate breakdown at atmospheric pressure. Piezoelectric transformers (PTs) are solid-state transformers that can produce large gains in voltage, which along with their modest size, makes them attractive candidates for use in plasma production. In this paper, we use a low-voltage power supply in line with a PT to produce an APP jet (APPJ). While operating at the resonance frequency of the PT (88 kHz), plasma jets were generated with input voltages as low as 10 V. The electrical and optical characteristics of the piezoelectric-driven jet were compared to an APPJ produced with a high-voltage sine wave of comparable operating frequency. Both APPJs were examined in helium and argon for a variety of different flow rates and operating voltages. In argon, the length of the jets was nearly identical for all operating parameters but produced different discharge currents. In helium, the discharge currents were similar but the lengths of the jet differed. Optical emission spectroscopy showed similar chemical composition between the two jets for both feed gases. Together, the results suggest that the piezoelectric material has an influence beyond simply amplifying voltage but can be successfully integrated to meet the requirements needed for plasma production. [ABSTRACT FROM AUTHOR]

This paper investigates a mainstream metal 3-D printing technique (i.e., direct metal laser sintering of stainless steel {SS} 316L) and two relatively new metal additive manufacturing methods (i.e., lost-wax casting of sterling silver using digital light projection/stereolithography-printed wax masters, and binder inkjet printing of SS 316L) for the fabrication, using tens-of-microns-sized voxels, of freeform, finely featured, mesoscaled metal structures part of compact systems. Characterization of the 3-D printing methods included assessment of dimensional accuracy and in-plane minimum feature size, measurement of vacuum outgassing, quantification of porosity, and estimation of thermal and electrical properties. The data demonstrate that binder inkjet printing of SS 316L has associated the smallest in-plane offset, out-of-plane offset, and eccentricity of nominally symmetric features while showing ultra-high-vacuum compatibility, low porosity, and intrinsic electrical and thermal properties close to those of bulk metal. Characterization of binder inkjet-printed SS 316L MEMS cantilevers shows repeatable micron-level linear actuation and a near-isotropic Young’s modulus of the printed material close to the bulk value. Also, characterization in air at atmospheric pressure and room temperature of binder inkjet-printed SS 316L MEMS corona discharge ionizers with 32 high-aspect-ratio tips (25 tips/cm2, 5 mm tip height, 141.7 $\mu \text {m} \pm 3.2 ~\mu \text{m}$ tip radii) resulted in 8.7-kV start-up voltage and up to $422~\mu \text{A}$ total emission current; no evidence of tip degradation was found via optical inspection and device weighting after continuous IV characterization and a 12-h test ($300~\mu \text{A}$ , 13.5 kV). In addition, high-resolution microscopy of binder inkjet-printed SS 316L electrodes part of a novel, compact, multi-electrode harmonized Kingdon ion trap estimates at $\sim 15~\mu \text{m}$ the maximum height difference between the printed part and the digital model–making possible the implementation of portable, high-resolution mass spectrometers. [2018-0052] [ABSTRACT FROM AUTHOR]

This paper describes the development and characterization of a wireless pressure monitoring system (WPMS) using an integrated radio frequency (RF) transceiver for applications such as monitoring of exerted vapor pressure variations of gases, volatile organic compounds (VOCs), and water vapor. Parametric sensing and environment detection using integrated approach are the key drivers for modern sensor technology. Our WPMS has an operating frequency band of 2.3152–2.6478 GHz. It has been developed using a pressure transducer, voltage-controlled oscillator, amplifier, and transmit/receive filtennas (filtering antennas). Transmitting antenna has been used for radiating RF signal (conditioned pressure information), while reflecting the undesired harmonics. Filtering antenna at the receiver side has been used to detect the desired RF signal, while filtering out the undesired signal. Experiments have been performed for monitoring a pressure variation of 0–50 kPa for a distance of 3 m from the transmitter. The pressure sensitivity of the system is 6.4 MHz/kPa with a good linearity response. Wireless temperature monitoring using our constructed RF sensor has also been demonstrated. The temperature sensitivity of wireless temperature monitoring system is about −662.2 kHz/°C between −55 °C and 130 °C. Calibration curve and polynomial fitting equations have been provided for evaluating pressure and temperature variations. The main advantages of this integrated system are integrated design, high-pressure/high-temperature sensitivity response, good linearity response, lower cost, less complexity, handheld, compact size, increased flexibility, and indigenous subsystems. The proposed system is suitable for wireless pressure/temperature monitoring applications in gas/oil industry, VOC industry, and steam industry. [ABSTRACT FROM AUTHOR]

In this paper, Ar–H2 plasma is studied by the nonintrusive optical emission spectroscopy method. The emission spectra of excited species of hydrogen and argon are observed and measured. The effect of an increase in hydrogen gas flow in the Ar–H2 plasma is studied experimentally. The variation in peak intensity and broadening of $\text{H}_{\alpha }$ line with increased hydrogen gas flow rates is examined. It is noticed that the peak intensity of $\text{H}_{\alpha }$ line is very sensitive to hydrogen gas flow rate while the broadening of the line is found to be constant. The broadening of $\text{H}_{\alpha }$ line is observed to be a Lorentzian profile. In addition to this observation, the electron temperature was computed using Boltzmann’s plot method. It is learned that the theoretical and the experimentally evaluated electron densities are not in close agreement with each other. Therefore, the estimation of electron density from the electron temperature will not always be a reliable method in the case of such atmospheric plasma. The saturation effect of electron density and the quenching of Ar I emission lines are also observed and discussed. [ABSTRACT FROM AUTHOR]

This paper is aimed to identify the mechanism that atmospheric pressure plasma jet (APPJ) damages malignant melanoma (B16-BL6 cells) cultured in vitro through the induction of oxidative stress. After being exposed to APPJ with different time durations, the reactive species of H2O2 and NO2− inside cell culture medium, together with a series of biochemical parameters including the cell viability, cell morphology, DNA damage, intracellular reactive oxygen species (ROS) and antioxidant capacity, are measured. The results reveal that there are obvious increases of H2O2 and NO2− in the plasma-irradiated medium. And the cell viability, intracellular total antioxidant capability (T-AOC), and glutathione (GSH) contents decrease with the exposure to APPJ in a time-dependent manner compared with the untreated cells, i.e., 0-s group ($p < 0.05$). Besides, the intracellular malondialdehyde (MDA), ROS contents, and the degree of cellular damage increase significantly with 30, 60, and 90 s of plasma treatment ($p < 0.05$). Furthermore, the pretreatment with N-acetyl cysteine, which is a free radical scavenger, can markedly prevent the decrease of cell viability, T-AOC, and GSH content, the increase of MDA, ROS contents, and the degree of cellular damage caused by 90-s exposure to APPJ. These research findings suggest that low-temperature plasma exerts its cytotoxic effects on melanoma cancer cells mainly through the ROS inside cells induced by reactive oxygen and nitrogen species generated in gaseous and liquid phases, which ultimately cause oxidative stress-evoked damage to cellular components. [ABSTRACT FROM AUTHOR]

The influence of ambient air species especially humidity is an ever-present challenge for atmospheric pressure plasma jet applications. Especially, where the plasma-induced effects are extremely sensitive to humidity, such as in the field of plasma medicine, an understanding of the influence of ambient species diffusion on plasma chemistry and on reactive component composition is crucial. In this paper, we investigate the influence of ambient humidity versus feed gas humidity on the production of reactive components by atmospheric pressure plasma jets. By the use of a shielding gas curtain, we control the surrounding atmosphere around the active effluent region of the investigated argon RF-plasma jet (kinpen) and control the gas humidity of the ambient gas. By quantum cascade laser absorption spectroscopy and by Fourier transformed infrared (IR) absorption spectroscopy, the effect of diffusing surrounding molecular species on the chemistry of the long-living reactive oxygen species is investigated. Mechanisms of H2O2 and O3 production are studied. In this paper, we have quantified the influence that ambient species, namely, water molecules, have on the reactive species’ generation in the gas phase. It is shown that the effect of ambient humidity is important for the long-living species production, feed gas humidity, however, has the much stronger effect. Finally, with the focus of applications in plasma medicine, the cell viability of human skin cells (HaCaT keratinocytes) as a function of feed gas and ambient gas humidity is compared. [ABSTRACT FROM PUBLISHER]

Nonthermal atmospheric pressure plasma jets (APPJs) are characterized by very reactive chemistry without the need of elevated temperatures. Also, plasma jets are capable of producing cold plasma plumes that are not spatially confined by electrodes, which makes them very attractive for biomedical applications. In this paper, we investigate the antimicrobial efficiency of a simple plasma jet device operating with pure He as working gas. The device was driven by an ac power supply operated at 31.0 kHz, 13.0 kV amplitude with mean power around 1.8 W. The jet was directed perpendicularly on a standard Petri dish (Ø 90~mm\times 15 mm) filled with agar. The jet fungicidal efficiency was tested against Candida albicans (reference strains SC 5314 and ATCC 18804) and five clinical isolates from previously obtained denture stomatitis lesions. In this paper, the effects of treatment time and distance to the target were evaluated. In most treatments the samples did not have direct contact with the plasma plume; therefore, the reactive oxygen species produced by interaction between the plasma jet and ambient air were the principal inactivate agent. [ABSTRACT FROM PUBLISHER]

In this paper, the mechanisms and characteristics of the pulsed dielectric barrier discharges in Ar and N2 at atmospheric pressure are analyzed and compared by means of numerical simulation based on the 1-D fluid model. Under different operating conditions, including gap width dg , dielectric thickness ds , and relative dielectric constant \varepsilon r , the important characteristic quantities of describing the discharge, i.e., maximum discharge current density Jm , averaged electron density \mathrmNe-\mathrm {ave} , and averaged dissipated power density P\mathrm {ave} , are observed and studied in detail. This paper gives the following significant results. In Ar, the discharge occurs after the gap voltage has reached its maximum and is in the form of two short discharge current density pulses. In N2, the discharge starts from the increase of the gap voltage and presents the smooth development in a longer time being nearly equal to the pulsewidth. For the two gases, Jm , \mathrmNe-\mathrm {ave} , and P\mathrm {ave} decrease with the increase of d\!g , and these characteristic quantities decrease with the increase of ds , or with the decrease of \varepsilon r . In addition, the discharges in Ar maintain in the atmospheric pressure glow discharge (APGD), but the discharges in N2 operate in the varying discharge modes, including the APGD, the weak APGD, and the atmospheric pressure Townsend discharge. The development of the APGD in N2 requires the smaller gap width, the thinner dielectric thickness, and the larger relative dielectric constant. [ABSTRACT FROM PUBLISHER]

Preionization for atmospheric pressure discharge plasma has been employed in several pulse gas lasers, while dielectric barrier discharge has often been utilized for ozone generators. A single ozone-generating device combining both preionization discharge and dielectric barrier discharge is investigated in this paper. The preionizing electrode configuration consisted of a wire-dielectric-plate with a 1.5-mm-thick aluminum oxide (Al2O3) barrier with relative permittivity \varepsilon \mathit {r} of about 10. Wire electrodes (0.8-mm diameter) and plate electrodes were all made of stainless steel. A barrier discharge was generated by applying a pulse voltage between the plate electrode and the wire electrodes across the dielectric, which was served as a preionizer. The main discharge was produced immediately after preionization by applying a high-voltage pulse between the wire-plate electrodes with a gap distance of 10 mm. This paper examines the temporal and spatial evolution of the discharge with and without preionization. Results from a high-speed framing camera indicate that preionization increases the volume of the main discharge, resulting in a streamer-like discharge system with preionization, which is an effective method for ozone generation. [ABSTRACT FROM PUBLISHER]

This paper deals with the realization of a diffuse dielectric barrier discharge in air at atmospheric pressure using a high-voltage pulse generator operating in a single-pulse mode and at frequencies of tens of hertz. This paper is focused on the effects of the series resistor and dielectric materials. It is shown that the parameters of the external circuit strongly influence the discharge mode. [ABSTRACT FROM PUBLISHER]

This paper presents an experimental investigation of ionization waves’ (IWs’) propagation in a nanosecond-pulse dielectric barrier discharge at atmospheric pressure in air. The effect of the rise time and pulse duration on IW propagation is studied by an intensified charge-coupled device, and the mechanism of the discharge propagation is analyzed. The experimental results show that the discharge produced in the rise time of the applied voltage develops in a structure of discontinuous sphere, while the discharge produced in the falling time exhibits a continuous form due to the effect of space charge. Furthermore, the rise time of the applied voltage has a significant influence on the velocity of IWs, and the maximal velocity of IWs rapidly decreases from 0.08 to 0.008 mm/ns when the rise time of the applied voltage increases from 50 to 300 ns. However, the pulse width has almost no influence on the velocity of IWs. The electric field distortion caused by both the propagation of IWs and the accumulation of surface charges is responsible for the formation and propagation of IWs. [ABSTRACT FROM AUTHOR]

Plasma needle is a novel design of a plasma source at atmospheric pressure to achieve a nonthermal plasma jet. The advantage of the plasma needle is that it can be operated in open air, outside a vessel. The plasma that is generated with the plasma needle is small (about 1 mm) and nonthermal; the temperature of the neutral particles and ions are in about room temperature and suitably can be used to treat living biological cell without damaging the cell. In this paper, we report design, development, and electrical and optical emission spectroscopy characterization along with applicability in biomedical investigation of a dc plasma needle that can easily interact with living cell/human finger. Argon gas is used to operate the plasma needle, and the plasma jet is operated on water surface instead of human finger for stability during the characterization. The electrical diagnostics of the plasma needle shows that the discharge is pulse in nature. It has been observed that the increased in the applied voltage increasing the discharge frequency without affecting the discharge voltage and discharge current. The frequency of the discharge is found to increase almost linearly with increasing applied voltage. The estimated excitation temperature by using Boltzmann’s plot method from OES is found almost independent on the applied voltage. The temperature is found to increase with increasing ballast resistance at above a threshold value of the resistance, below of which, the temperature is found almost constant. The variation in separation between the tip of the plasma needle and the water surface did not show any considerable variation in temperature when the separation is higher than 5 mm. However, considerable increase in temperature is observed when the separation is decreased below 5 mm. The developed plasma needle has been also used to treated Nova Blue bacteria and water collected from drinking water dispenser of pets, and the results shows the applicability to treat microbes in localize region. [ABSTRACT FROM AUTHOR]

In this paper, a low-cost and portable plasma device is developed to generate atmospheric pressure nonthermal air plasma jet for safe and effective biomedical applications. The device mainly consists of a pen electrode, a high-frequency ac power supply, an ac/dc module, and a dc air pump, and it totally costs only U.S. $63 and has a small size of 280 mm $\times190$ mm $\times180$ mm. The appearance of two-mode discharge of half-wave and full-wave breakdown with the changing of applied voltage is identified, and the length of the plasma jet is optimized through studying on the influences of distance between two electrodes, gas flow rates, and hole diameters of the gas outflow in ground electrode. Stronger plasma with a longer jet length of 12 mm can be obtained in the full-wave breakdown discharge mode, while moderate plasma with a length of 8 mm can be obtained in the half-wave breakdown discharge mode. The discharge characteristics of the device such as the main generated active particle, voltage and current, discharge power, and operation temperature are obtained. It is shown that rich active species for biomedical application can be generated at low power of approximate 2 W and low operation temperature of approximate 40 °C. The developed device is tested for biomedical application, and the results of effective sterilization of C. albicans and blood coagulation are obtained. [ABSTRACT FROM AUTHOR]

A 2-D fluid model is developed to study the pulsed discharges with pin--plane electrode in atmospheric pressure. A positive streamer forms at the pin electrode connecting to the applied voltage and then propagates toward to the ground plane electrode (cathode). Simulation results show if the streamer head is close enough to the cathode, in front of the original streamer a new streamer forms, and simultaneously a second positive current peak is observed, suggesting that the discharge mode transforms into glow mode. Otherwise, the discharge operates at corona mode. The characteristics of the two typical discharge modes are analyzed through the spatiotemporal evolution behaviors of conduction current, electron density, electric field, and electron flux. The transition between corona and glow modes depending on the discharge parameters such as applied voltage, curvature radii, and secondary electron emission coefficients are studied in this paper. It should be noted that no matter what discharge mode is, discharge with reversed direction appears at the falling edge of voltage pulse, which is caused by space charges [ABSTRACT FROM AUTHOR]

Surface dielectric barrier discharge (DBD) has recently received growing interest for enormous application potential in various fields. In this paper, the optical observation of surface DBD is conducted by an intensified charge-coupled device camera from top view in the atmospheric air. Spacial and transient characteristics of discharge phenomenon in atmospheric pressure air have been, respectively, visualized with the exposure time of 100 ms and 5 μs. The discharge area is obtained by calculating the number of pixels in MATLAB software at different electrical parameters and different high-voltage electrode configurations with microsecond time scale. Experimental measurements show that the diffuse discharge during the negative-half cycle has good uniformity and stability compared with filamentary discharge during the positive-half cycle. The results offer a new estimated method for the discharge area. [ABSTRACT FROM PUBLISHER]

The bare conductor in switchgear constitutes complicated air gaps, and their AC withstand characteristic will obviously affect switchgear insulation performance. In this paper, AC withstand tests of various types of air gap were carried out. The air gap samples were rod-plane air gap and 4 typical types of air gap from the bus chamber of 40.5 kV metal-enclosed switchgear. The samples were tested in climate chamber where high altitude environment was simulated. And correction of withstand voltage for switchgear air gaps at low air pressure were conducted. Test results indicate that, the withstand characteristic of 4 typical types of air gap in switchgear are different from that of rod-plane air gap. The relationship between withstand voltage Uw and air gap distance d is nonlinear. The influencing characteristic exponent n of air pressure on Uw is related with air gap type. Linearity value m and air pressure index n are independent to some degree. An equation was proposed to express the relationship of Uw with air gap distance d and altitude H, and this equation can be used to calculate the safety distance of air gaps in switchgear under low air pressure situations. The results are significant for the design and selection of switch devices. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to investigate the effect of nonthermal atmospheric pressure plasma jet on human breast cancer and normal cells. High voltage, dc-pulsed power supply was used to generate low temperature helium plasma in atmospheric pressure. In this paper, cancer and normal cells were exposed to plasma during four time steps. For further exploration, Doxorubicin as common chemotherapy drug was employed to compare the efficacy of plasma treatment with convectional cancer therapy. Also, the Caspase-Glo 3/7 assay was obtained to reveal the death process of cancer and normal cells. The results of MTT and apoptosis assay showed that the plasma treatment has drastically reduced the viability of breast cancer cells, while it has no significant damage to the normal cells. In addition, after plasma treatment three different zones were formed in the plate, which will represent the detachment of cells from plate surface. Moreover, adding 5% oxygen to the helium plasma will lead to enhancement of cancer cells viability reduction. In addition, the outcome of this paper has verified that the plasma treatment successfully overcomes drug treatment in inhibition of the cancer cells viability, while decreases the adverse effect of drug treatment. [ABSTRACT FROM PUBLISHER]

The effects of the frequency on the electrical characteristics in a dielectric barrier discharge in pure helium excited by repetitive voltage pulses with the frequency f from 5 to 500 kHz are systematically investigated by means of a 1-D fluid model under different operating conditions, including gap width dg, secondary electron emission coefficient \gamma, dielectric thickness ds, and dielectric constant \varepsilonr. The important characteristic quantities of describing the pulse discharge, i.e., discharge current density Jg, averaged electron density Nave, averaged dissipated power density Pave, and the axial distributions of both electron density Ne and electron temperature Te, are calculated and analyzed in detail. This paper gives the following significant results. Nave increases with increasing f and Pave is almost proportional to f. Especially, there is a characteristic frequency of \sim50~kHz, namely, when f is lower than \sim50~kHz, Jm1 (peak value of Jg in the first discharge) decreases evidently with increasing f, and then changes very slightly for fs larger than \sim50~kHz. In addition, with the increase of f, Jm2 (peak value of Jg in the second discharge) increases very slightly for small ds and the reverse is true for large ds. The frequency dependence of Jm2 for different \varepsilonrs is similar to that by changing ds. For a fixed frequency, the change of Jm1 with \gamma is very small, which differs from that at low frequencies. In addition, Jm1 and Jm2 decrease with increasing ds and increase with increasing \varepsilonr, but there are almost constant \Delta Jm1 and \Delta Jm2 for high frequencies. When the frequency is larger than \sim50~kHz, there will be the second peak of Ne outside the cathode sheath in the first discharge, and both large ds and small \varepsilonr can result in the formation of the evident peak of Ne nearby the momentary anode. It should be noted that the analysis in this paper pertains only to the incompressible motion of the plasma. [ABSTRACT FROM PUBLISHER]

In this paper, an atmospheric-pressure dielectric barrier discharge is used to modify the surface of the epoxy material and enhance the dissipation of surface charge to reduce the accumulation of surface charge. In the experiments, atmospheric-pressure air dielectric barrier discharge is driven by a microsecond pulse generator. Surface properties of epoxy before and after the plasma treatment are characterized by water contact angle, surface potential, and surface/volume conductivity measurements. Atomic force microscope and X-ray photoelectron spectroscopy are used to investigate the changes of the morphology and the chemical composition of the epoxy surface. Experimental results indicate that the surface of epoxy is etched by the plasma and the increase of the surface roughness enhances the surface insulation ability. The O radicals in plasma and the carbonyl groups formed on the surface make the surface charge trap shallower, change the epoxy surface composition then increase the surface conductivity and accelerate surface charge dissipation. When the epoxy is treated for an appropriate time, the epoxy surface insulation performance will be enhanced obviously and the surface charge dissipation will be accelerated. [ABSTRACT FROM PUBLISHER]

This paper explores the effects of tube shape and pin electrode diameter on the plume generation and electrical characteristics in atmospheric pressure helium plasma jets generated from a centered-pin electrode inside a dielectric tube. The quartz-covered (or bare) pin electrode and different shapes of the dielectric tube (straight cylinder or conical shape) are employed and their effects are investigated. Optical emission spectra are obtained at different positions along the coaxial direction to determine the axial distributions of the electron excitation temperature for the straight cylinder and conical jets. The rotational temperatures for the both jets are also compared. [ABSTRACT FROM PUBLISHER]

Unintended atmospheric pressure dc arc is very common and harmful in many power applications. There is still no effective detection method for series dc arcs. In this paper, the initial features of current and electromagnetic signal of series dc arc are investigated on an arc generation platform. It is found that the current varies abruptly at the starting moment of the arc, and then a series of stochastic pulses can be observed. Corresponding to the current pulses, electromagnetic pulses are also measured by antenna simultaneously. Based on the abrupt current variation and unique pulse-time pattern features of the series dc arc, a fault detection algorithm is proposed. The proposed algorithm is proved to be robust and effective. [ABSTRACT FROM PUBLISHER]

The atmospheric-pressure plasma jets and their applications discussed here are a topic of great interest in the fields of science and technology. As is referred to in this paper, the plasma generated in a laboratory setting is described as the dielectric barrier discharge like. The atmospheric-pressure plasma jets of argon (Ar) and neon (Ne) are generated using an ac-power supply with a frequency of 24 kHz and a voltage of 12 kV at room temperature. For the first time in the world in this context, the vibrational spectra Fourier Transform Infrared of coumarin molecule (abbreviated here as 1CMN) dissolved in ethanol and methanol are analyzed after the atmospheric-pressure plasma treatment (APPT) of argon and neon. Plasma jet spectroscopy is used to investigate FT-IR spectra of coumarin before and after APPT process, which takes only 3 min. Also, the changes of structure and the interaction of the plasma and the molecule (coumarin) dissolved in solvents are examined, and the vibration modes of the 1CMN molecule before and after APPT are investigated. Thus, the final structure of the molecule can be explained with respect to the vibrational characteristics of the 1CMN molecule, and the photochemistry of this compound is studied under the conditions of this experiment. [ABSTRACT FROM PUBLISHER]

The conventional ways of processing natural gas into more efficient and economical fuels usually have either low conversion rate or low energy efficiency. In this paper, a new approach of methane liquefaction is proposed. Instead of direct treatment of only natural gas, plasma-activated methane is reacting with liquid fuel. In this way, methane molecules are directly incorporated into liquid fuel to achieve liquefaction. Nanosecond-pulsed dielectric barrier discharge and atmospheric pressure glow discharge are used here to ensure no local heating in gas bubbles. Effects of both discharges on methane reaction with liquid fuel are investigated, and mass and chemical changes in liquid are observed. Preliminary results show fixation of methane in liquid fuel. [ABSTRACT FROM PUBLISHER]

This paper was prepared in response to the growing interest in the numerical simulation of the gliding arc (GA) discharge. Our approach is rather simple 2-D modeling of the GA, in the plane that is parallel to the gas flow and perpendicular to the discharge current. We used Fluent software with a subroutine that calculates electric conductivity of argon plasma and local heat release due to the electric current of predetermined value. Electric conductivity of argon was calculated as function of the reduced electric field and gas temperature. Our results show that this approach can give very useful information about the gas-discharge interaction, which is very important to capture the discharge behavior. Presence of discharge inside the gas flow significantly disturbs both of them. Gas-discharge slip velocity exists at least at the beginning of GA development cycle even if there is no mechanism of the discharge deceleration. Just original spark formation associated with the electrode surfaces results in the appearance of this “independent” slip. In the cases of reasonably high gas velocities and discharge currents, this initial slip does not disappear during the discharge lifetime and can result in significant discharge cross-sectional elongation along the gas flow. Electric field fluctuation at any particular part of the discharge channel can be very large, and this can have the major effect on the nonequilibrium ionization and chemical processes. [ABSTRACT FROM PUBLISHER]