Influence Of Pulse Parameters Research Articles

Air disinfection by nanosecond pulsed DBD plasma

Atmospheric pressure dielectric barrier discharge (DBD) plasma is an emerging and promising technique for air disinfection in public environments. Power supply is a crucial factor but it remains unclear about its impacts on the air disinfection performance of plasmas. In this work, a nanosecond (ns) pulsed power supply was applied to drive an in-duct grating-like DBD array to achieve fast single-pass air disinfection. The influence of pulse parameters and environmental factors on both the discharge characteristics and the single-pass bacterial inactivation efficiency were uncovered. At a close relative humidity (RH) level, the efficiency was dominated by the discharge power, namely, specific input energy could serve as the disinfection dose. A higher frequency, shorter pulse rising time, and suitable pulse width are preferred to obtain a higher Z value. The pulsed source was not notably superior to an alternating current source, or even worse at a low voltage frequency at the same discharge power. Airflow humidity was a predominant factor to improve the efficiency and a single-pass efficiency of ∼ 99% and a Z value of 2.2 L/J were achieved under an optimal RH of 50%–60%. This work provides fundamental knowledge of ns-pulsed DBD on discharge characteristics and air disinfection behaviors.

Influence of pulse parameters on microstructure and corrosion characteristics of electrodeposited Ni-W alloy coating

Material characterization and electrochemical performance of the pulse plated Ni-W alloy coatings were assessed by varying duty cycles (0–50%) and pulse frequencies (10–500 Hz) under relatively low applied current density (0.1 mA·cm−2). Compared to DC electroplating, the pulse plating process exhibited lower cathodic current efficiency, and the obtained coatings displayed slightly lower W content. However, the surface roughness, hardness, and anti-corrosion properties of the coatings were improved due to common characteristics, such as grain refinement, fewer defects, and enhanced surface uniformity, associated with the pulse plating process. The Ni-W alloy coating produced at a medium pulse frequency of 100 Hz with duty cycles of 10% and 50% exhibited the highest hardness (5.34±0.33 GPa) and the best corrosion resistance (corrosion current density Ic: 9.62 μA·cm−2), respectively. These properties were significantly improved compared to those for the counterparts prepared by DC electroplating (hardness: 3.13±0.58 GPa; Ic: 10.89 μA·cm−2).

A microplasma device and its switching behavior triggered by modulated pulse signal

Since the physical and electrical properties of plasmas are similar to those of semiconductor devices, plasma devices have been proposed to be good candidates for switching controlled devices when applied in harsh environments. In the proposed paper, a microplasma device with a dielectric barrier structure constructed with three electrodes (two driven electrodes and one trigger electrode) is fabricated, and the electrical characteristics of the proposed device are investigated in 2 kPa of argon. From the experimental results, a stable conducting current is obtained through the two driven electrodes in the device due to gas discharge, since the hysteresis characteristic of discharge plasmas (discharge is still maintained when the driven voltage is below the breakdown voltage of the gas because of the existence of residual charge particles), the device can be switched from the OFF to ON state through pre-discharge by a pulse applied to the trigger electrode. While in the device ON state, this trigger voltage attracts channel charged particles to the surface of the dielectric layer, quenching the discharge plasma current and the device can be switched from ON to OFF state. The trigger pulse that makes the device switch successfully goes from single to continuous up to 80 kHz. The influence of pulse parameters on the switching process is also investigated, pulse amplitude and pulse width are found to be important to determine whether the device can switch ON or OFF, peak current after switching, and the response speed of switching ON current; however, these switching parameters are barely affected by the rise and fall time of the pulse. The results are significant for the application of microplasma switching devices.

Preparation of Cu2ZnSnS4@TiO2 nanotubes by pulsed electrodeposition for efficiently photoelectrocatalytic reduction of CO2 to ethanol

In this work, we reported a method of preparing Cu2ZnSnS4@TiO2 nanotubes (Cu2ZnSnS4/TiO2NTs) composite electrode by pulse electrodeposition and high-temperature vulcanization, which possesses high catalytic conversion efficiency for CO2 reduction and stable performance. In addition, the influence of pulse parameters on the morphology and photoelectrochemical properties of Cu2ZnSnS4/TiO2NTs composite electrode were studied in detail. The band gap of Cu2ZnSnS4/TiO2NTs is 1.39 eV, which is significantly reduced compared with TiO2NTs (3.27 eV). There are differences in the morphology, catalytic efficiency and product selectivity of the catalytic interface constructed by different pulse electrodeposition parameters. The photoresponse current of the composite electrode prepared by optimizing the parameters reaches −7 μA cm−2, and the ethanol yield is 7.0 μmol cm−2 after 5 h of photoelectrocatalytic reduction of CO2. No new phase was generated and the photocurrent density remained 33.2% of the original after the catalytic process, which indicated the Cu2ZnSnS4/TiO2NTs possess stable catalytic performance.

Microstructural investigation of nickel deposits obtained by pulsed current

Electrodeposited nickel coatings are applied in functional applications to modify or improve corrosion resistance, hardness, wear, magnetic, and other properties. In this work, Nickel deposits were produced by simple pulse electrodeposition using a free-additive Watts bath. It has been shown that pulse current deposition is able to produce coatings with excellent properties in morphology, particle distribution, structure, grain size, hardness and wear resistance. Pulsed techniques present a larger number of variables, so we propose to optimize the parameters which define the pulsed current to obtain deposits with improved properties. The optimization of the conditions of deposition was established and the influence of pulse parameters, namely, pulse on-time, off-time and average current density, on the grain size, surface morphology and crystal orientation was determined. The morphology of the coatings was characterized by observations in scanning electronic microscopy (SEM). X-ray diffraction in symmetric mode was also used to evaluate the structure and principal crystallographic orientations of the deposits. The study showed that pulse current results in better properties of deposits and significantly refined the crystal grain.

Ultrafast response of cubic silicon carbide to intense attosecond pulse light

In this paper we are motivated to numerically investigate the fundamental strong-field and attosecond response processes in wide band-gap solids, using the first-principle approach based on time-dependent density functional theory, advancing our understanding of fundamental strong-field and attosecond physics in solids. Taking cubic silicon carbide as a concrete example, the influence of pulse parameters on the ultrafast responses is demonstrated, which allows one to gain a useful independent insight into the interaction processes of attosecond light pulses with solids, revealing information currently not accessible by experiment. We also demonstrate control of the charge transfer and dielectric permittivity by intense attosecond pulse light. It is concluded that a single-cycle attosecond pulse light can be used to effectively manipulate the charge transfer and dielectric properties of wide-band gap materials with great potential for ultrafast device applications.

Pulse electrodeposition of nano-crystalline Ni-W alloy and the influence of tungsten composition on structure, microhardness and corrosion properties

In this work, nano-crystalline Ni-W alloy films with various tungsten compositions were deposited on mild steel substrate using pulse electrodeposition method. The influence of pulse parameters on composition, crystal structure, microhardness and corrosion properties were studied. The tungsten composition in Ni-W alloy deposits were influenced by pulse deposition parameters and it is varied from 9.51 at% (lower) to 27.7 at% (higher). The influence of tungsten composition on crystal structure, crystallite size, microhardness and corrosion properties were studied. The lower tungsten composition in Ni-W alloy deposit gives pure cubic crystal structure and the higher tungsten composition gives mixture of cubic and tetragonal crystal structure. The alloy deposited using higher pulse duty cycle and lower pulse frequency gives higher microhardness properties and corrosion resistance behaviors. The smallest crystallite sizes and 16–18 at% of tungsten composition in Ni-W alloys favor better microhardness and corrosion resistance properties.

Metal transfer of aluminum alloy double-wire pulsed GMAW with a median waveform

Abstract This paper proposes a double-wire pulsed gas metal arc welding (GMAW) process with a median current waveform based on traditional double-wire pulsed GMAW. A high-speed digital camera and digital oscilloscope were used to simultaneously record the metal transfer process as well as the voltage and current waveforms under different median currents. The median pulse was modeled as an exponential function and a mathematical model of the droplet diameter was established. Further, variation of the output current during the welding process and the influence of pulse parameters on the metal transfer process were accurately described. The results show that the median current has a significant impact on the metal transfer process. When the median current increases, the metal transfer period gradually decreases and the desired one drop per pulse (ODPP) mode, with a moderate droplet size and no droplet collision, is almost achieved within an appropriate median current range. As the median current gradually increases, the droplet diameter also increases but then begins to decrease as the median current further increases and gets closer to the peak current. The droplet offset distance first decreases considerably, then begins to increase, and droplet collision occurs as the median current continues to increase, resulting in an unstable transfer process. Initially, the transfer time decreases and then increases, followed by a subsequent decrease as the median current continues to increase.

Statistical analysis of pulsed laser beam welding repair strategies of nickel-base superalloys

Pulse shaping is a suitable option to adapt energy input and temperature gradients in the base material during filler wire assisted laser beam welding, although the influence on the temperature-depended microstructure and γ’-precipitation strengthening of Nickel-base superalloys as well as the process windows are not sufficiently understood so far. Therefore, the influence of pulse parameters, preheating temperature, hot-wire heating power and wire feeding rate on the deposition process and the resulting macro- and microstructure of similar Nickel-base superalloy joints of Inconel 738 low carbon (IN 738 LC) with Haynes (HS 282) filler are investigated. The statistical analysis of the multidimensional parameter space with respect to the geometric properties of the weld seams (dilution, aspect ratio and wetting angle) and hot-crack formation revealed high reliability and predictability concerning individual choice of suitable parameters in field repair application.

Influence of pulse parameters on the mechanical properties and electrochemical corrosion behavior of electrodeposited Ni-W alloy coatings with high tungsten content

Ni-W alloys with 16–28 at% tungsten (W) content were electrodeposited from citrate bath utilizing various pulse parameters. The influence of pulse parameters on microstructure, composition and mechanical properties was systematically studied. The corrosion behavior was analyzed in 1 M H2SO4 using potentiodynamic polarization and electrochemical impedance spectroscopy. Nanocrystalline Ni-W coatings were found to have superior corrosion resistance compared to their duplex nanocrystalline-amorphous counterpart. The corrosion behavior was rationalized based on semiconducting properties of oxide film using Mott–Schottky analysis and depth wise composition analysis utilizing X-ray Photoelectron Spectroscopy. An attempt is made to correlate corrosion current with intercrystalline defects.

Experimental studies on waveform distortion of pulse-modulated RF atmospheric-pressure discharge

The influence of pulse parameters on discharge characteristics has been studied, but no attention has been paid to RF waveform distortion in pulse-modulated RF discharges. In this paper, RF waveform distortions are experimentally studied. The results show that (1) the alpha to gamma mode transition can occur in one pulse discharge. (2) When the pulse discharge operates in alpha mode, RF current waveform (Idis) distortion varies continuously with time in one pulse cycle, and the time range displaying obvious distortion is from 0 to one-fourth of the cycle in an RF period. However, the Idis distortion jumps and the time range displaying obvious distortion is almost symmetrical with respect to the time instant corresponding to the positive-voltage maximum when the pulse discharge operates in gamma mode. (3) Idis distortion increases remarkably then slightly with increasing RF power when the pulse discharge operates only in alpha mode. The physical reasons for these results are discussed.

Influence of Pulse Parameters on the Morphology and Corrosion Resistance of Nickel-Graphene Composite Coating

Influence of Pulse Parameters on the Morphology and Corrosion Resistance of Nickel-Graphene Composite Coating

Evaluation of silver as an active direct ethanol fuel cell electrode catalyst prepared by pulsed current electrodeposition technique

Pulsed current electrodeposition of silver on graphite from non-cyanide bath has been employed. The influence of pulse parameters on electrocatalytic activity of Ag catalyst for ethanol oxidation in alkaline media have been evaluated by field emission scanning electron microscopy (FESEM), X- ray diffraction (XRD) and cyclic voltammetry (CV). The results reveal that the optimum condition can be obtained at 60 % duty cycle, 50 mAcm-2 average current density, 10 min. deposition time, and 10 Hz pulse frequency. The electrocatalytic activity and stability of Ag/C electrode prepared, at corresponding optimum condition, by pulse current (PC) and direct current (DC) electrodeposition for ethanol oxidation in alkaline media have been compared. The results illustrate that PC silver catalyst exhibits higher oxidation peak current density, higher surface coverage, higher poisoning tolerance as well as smaller charge transfer resistance, in alkaline ethanol solution, than that prepared by DC technique and thus can be used as an active anode material for direct ethanol fuel cell at a reduced cost.

The influence of pulse parameters on the downstream uniformity of linear-field jet array in argon

The nanosecond (ns) pulse excited plasma jet array shows merits of large treatment area and high chemical reactivity, while the pulse parameters influence the downstream uniformity of the ns pulse excited jet array significantly. In this paper, the downstream uniformity of the ns pulsed jet array with linear-field electrode structure is investigated by discharge image measurement at different amplitude of applied voltage, rising time and pulse repetition frequency (PRF). The voltage-current waveform and Schlieren image are measured and the electrical field distribution of the jet array is simulated to reveal the interaction mechanisms. The experimental results show that the divergence of side plumes becomes severer and the plume length of all three jet units becomes longer at higher applied voltage, which is caused by the enhancement of the electron energy and density. The shorter rising time also increases the transported charge and input energy and extends the length of the plasma plumes. At 0.5 L/min Ar flow rate, all of the lengths of plumes increase with PRF although the laminar regimes of the gas flows are reduced. At Ar flow rate of 1, 2, and 4 L/min, the middle jet is suppressed, which is analyzed by the electrical field distribution simulation. It is shown that the highest electric fields at the outside walls of side jet units, which suppress the propagation of ionization front from the orifice to the outer space of the middle jet. At lower Ar flow rate, there are severe depletion of electrons in the side jets by oxygen and penning ionization in the middle jet by background molecules, which result in the enhancement of the jet array downstream uniformity. The results are of importance to optimize pulse parameters for the realization of controllable and scalable pulse excited jet array for various applications.

The influence of pulsed parameters on the damage of a Darlington transistor * * Project supported by the Open Fund of Key Laboratory of Complex Electromagnetic Environment Science and Technology, China Academy of Engineering Physics (No. 2015-0214.XY.K).

Theoretical research on the heat accumulation effect of a Darlington transistor induced by high power microwave is conducted, and temperature variation as functions of pulse repetitive frequency (PRF) and duty cycle (DC) are studied. According to the distribution of the electronic field and the current density in the Darlington transistor, the research of the damage mechanism is carried out. The results show that for repetitive pulses with the same pulse widths and different PRFs, the value of temperature variation increases with PRF increases, and the peak temperature has almost no change when PRF is lower than 200 kHz; while for the repetitive pulses with the same PRF and different pulse widths, the larger the pulse width is, the greater temperature variation varies. The response of the peak temperature caused by a single pulse demonstrates that there is no temperature variation when the rising time is much shorter than the falling time. In addition, the relationship between the temperature variation and the time during the rising edge time as well as that between the temperature variation and the time during the falling edge time are obtained utilizing the curve fitting method. Finally, for a certain average power, with DC increases the value of temperature variation decreases.

Study of metal transfer control in underwater wet FCAW using pulsed wire feed method

A metal transfer control method based on pulsed wire feed technology is adopted to ameliorate the underwater flux-cored arc wet welding quality. The stability of the welding process is improved with appropriate pulse parameters. The influences of pulse parameters on the metal transfer process are clarified using an X-ray transmission method. Pulse frequency has more of an effect on weld appearance and welding stability than pulse duty factor. Thirty to forty hertz is an appropriate frequency bound for a stable metal transfer process. The repelled metal transfer percentage decreases with increasing droplet growth speed. The inertia force shortens the metal transfer period and prompts droplet transfer into the pool. When the pulse frequency is less than 40 Hz, the base speed time is long enough for the inertia force to act on the droplet. But if the pulse frequency is below 20 Hz, the peak wire feed speed will be sustained for a long time, and the short-circuit frequency increases from 1 to 2.5 Hz; as a result, the welding stability and the welding appearance deteriorate. For the wire employed in this study, better welding stability is obtained at 30 Hz, while the pulse duty factor is 2.

Analysis of Dynamic Processes in Single-Cell Electroporation and Their Effects on Parameter Selection Based on the Finite-Element Model

Pulsed electric fields have recently been the focus of considerable attention because of their potential application in biomedicine. However, their practical clinical applications are limited by poor understanding of the interaction mechanism between pulsed electric fields and cells, particularly in the process of electroporation and its effect on parameter selection. This paper established a multishelled dielectric model based on finite elements to simulate and analyze the processes involved in electroporation. In particular, the processes include the dynamic development of the pore radius and electroporation region: the distribution of recoverable, nonrecoverable, and nonelectroporation areas on the cell; and the influence of pulse parameters on varying degrees of electroporation. Results showed that membrane conductivity, pore density, transmembrane potential, and distribution of pore radii are functions of time and position on the cell. The electroporation areas were divided into recoverable, nonrecoverable, and no-electroporation pores. For $10~\mu \text{s}$ , 1.5-kV/cm pulse was observed in the regions exposed to sufficiently high transmembrane voltage (1 V), electroporation occurred, membrane conductivity and pore density (up to $10^{\mathrm {16}}/\text{m}^{\mathrm {2}})$ rapidly increased with time, and electroporation areas increased gradually and were mainly distributed in the range 0°–70° (recoverable pore [0°, 35°], nonrecoverable pore [35°, 70°], and no-electroporation pore [70°, 90°]). Electric field strength was the major factor that induced electroporation, particularly in the recoverable pore, but it had minimal effect on pore expansion. However, pulse duration affects the nonrecoverable pore, such that the high-intensity wide pulse is more useful in the field of irreversible electroporation. The high-intensity short pulse can increase permeability and maintain cell viability.

Surface morphology and crystal orientation of electrodeposited tungsten coatings with different pulse parameters

This study was conducted to investigate the influence of pulse parameters on the surface morphology and crystal orientation of the tungsten coatings electrodeposited on pure copper substrates. The deposited coatings were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS). SEM analysis indicates that pulse parameters have significant influences on the surface morphology of the deposited coatings. Meanwhile, the change in grain size of the tungsten coatings demonstrates that the change in frequency and duty cycle could cause the variation of nucleation rate and grain growth of deposits. Moreover, no obvious diffusion layer at the coating/substrate interface is found by line analysis of EDS. XRD results reveal that tungsten coatings are of bcc structure and the preferred orientation of the deposits varies with duty cycle and period.

The discharge characteristics of surface dielectric barrier discharge sustained by repetitive nanosecond pulses in open air

A nanosecond pulsed surface dielectric barrier discharge (NPSDBD) is a promising method for flow control and combustion. We systematically investigated the influence of pulse parameters on the discharge characteristics of NPSDBD, especially on the conduction current of discharge and the energy deposition curves. Meanwhile, the differences of the characteristics of the discharge generated by positive pulses and negative pulses are focused in this paper. The underlying physics is also discussed. Four different discharge regimes of NPSDBD are presented, which can be distinguished by the temporal emission behaviors of discharge and the conduction current of discharge. The transitions of four discharge regimes were also investigated by changing the pulse amplitude, repetitive rate, and voltage polarity. It was found that it is easier to translate quasi-uniform discharge to filamentary discharge or transition mode for the repetitive pulses with a negative polarity. A phenomenological model was proposed to explain the differences between a positive repetitive pulse discharge and a negative repetitive pulse discharge.

Influence of Pulse Parameters on the Microstructure of Ceramic Oxide Coatings Produced on Al Alloy by Pulsed DC Plasma Electrolytic Oxidation

Influence of Pulse Parameters on the Microstructure of Ceramic Oxide Coatings Produced on Al Alloy by Pulsed DC Plasma Electrolytic Oxidation