Effect of pulse voltage rising time on discharge characteristics of a helium-air plasma at atmospheric pressure

In this paper,the influence of voltage rising time on a pulsed-dc helium-air plasma at atmospheric pressure is numerically simulated.Simulation results show that as the voltage rising time increases from 10 ns to 30 ns,there is a decrease in the discharge current,namely 0.052 A when the voltage rising time is 10 ns and 0.038 A when the voltage rising time is 30 ns.Additionally,a shorter voltage rising time results in a faster breakdown,a more rapidly rising current waveform,and a higher breakdown voltage.Furthermore,the basic parameters of the streamer discharge also increase with voltage rise rate,which is ascribed to the fact that more energetic electrons are produced in a shorter voltage rising time.Therefore,a pulsed-dc voltage with a short rising time is desirable for efficient production of nonequilibrium atmospheric pressure plasma discharge.

Scaling of rise time of drive current on development of magneto-Rayleigh–Taylor instabilities for single-shell Z-pinches

In fast Z-pinches,rise time of drive current plays an important role in development of magneto-Rayleigh–Taylor(MRT)instabilities.It is essential for applications of Z-pinch dynamic hohlraum(ZPDH),which could be used for driving inertial confinement fusion(ICF),to understand the scaling of rise time on MRTs.Therefore,a theoretical model for nonlinear development of MRTs is developed according to the numerical analysis.It is found from the model that the implosion distance L=r_(0)-r_(mc)determines the development of MRTs,where r_(0)is the initial radius and rmc is the position of the accelerating shell.The current rise timeτwould affect the MRT development because of its strong coupling with the r;.The amplitude of MRTs would increase with the rise time linearly if an implosion velocity is specified.The effects of the rise time on MRT,in addition,are studied by numerical simulation.The results are consistent with those of the theoretical model very well.Finally,the scaling of the rise time on amplitude of MRTs is obtained for a specified implosion velocity by the theoretical model and numerical simulations.

The effect of pulse voltage rise rate on the polypropylene surface hydrophilic modification by ns pulsed nitrogen DBD

The nanosecond(ns) pulsed nitrogen dielectric barrier discharge(DBD) is employed to enhance the hydrophilicity of polypropylene(PP) surface and improve its application effect.The discharge characteristics of the ns pulsed nitrogen DBD with different pulse rise times(from 50to 500 ns) are investigated by electrical and optical diagnostic methods and the discharge uniformity is quantitatively analyzed by image processing method.To characterize the surface hydrophilicity,the water contact angle(WCA) is measured,and the physical morphology and chemical composition of PP before and after modification are analyzed to explore the effect of plasma on PP surface.It is found that with increasing pulse rise time from 50 to 500 ns,DBD uniformity becomes worse,energy efficiency decreases from 20% to 10.8%,and electron density decrease from 6.6 × 10^(11)to 5.5 × 10^(11)cm^(-3).The tendency of electron temperature is characterized with the intensity ratio of N_(2)/N_(2)^(+)emission spectrum,which decreases from 17.4 to15.9 indicating the decreasing of T_(e) with increasing pulse rise time from 50 to 500 ns.The PP surface treated with 50 ns pulse rise time DBD has a lower WCA(~47°),while the WCA of PP treated with 100 to 500 ns pulse rise time DBD expands gradually(~50°–57°).According to the study of the fixed-point WCA values,the DBD-treated PP surface has superior uniformity under50 ns pulse rise time(3° variation) than under 300 ns pulse rise time(8° variation).After DBD treatment,the increased surface roughness from 2.0 to 9.8 nm and hydrophilic oxygencontaining groups on the surface,i.e.hydroxyl(-OH) and carbonyl(C=O) have played the significant role to improve the sample’s surface hydrophilicity.The short pulse voltage rise time enhances the reduced electric field strength(E/n) in the discharge space and improves the discharge uniformity,which makes relatively sufficient physical and chemical reactions have taken place on the PP surface,resulting in better treatment uniformity.

The Neutron-Gamma Pulse Shape Discrimination Method for Neutron Flux Detection in the ITER

The neutron flux monitor （NFM）, as a significant diagnostic system in the International Thermonuclear Experimental Reactor （ITER）, will play an important role in the readings of a series of key parameters in the fusion reaction process. As the core of the main electronic system of the NFM, the neutron-gamma pulse shape discrimination （n-γ PSD） can distinguish the neutron pulse from the gamma pulse and other disturbing pulses according to the thresholds of the rising time and the amplitude pre-installed on the board, the double timing point CFD method is used to get the rising time of the pulse. The n-γ PSD can provide an accurate neutron count.

Rising Women's Occupations in Modern Times

IN traditional Chinese society, having an occupation, as a means of making a living, was the "privilege" of women at lower levels of society. Married and unmarried women who had servants were sneered at if they had an occupation. The work that lower class women did was generally related to production and labor, market exchange, communications

Genetic Algorithm Based Speed Control of PMDC Motor Using Low Cost PIC 16F877A Microcontroller

This paper mainly aims at proposing an effective method of speed control of the low power motors like Permanent Magnet Direct Current (PMDC) motor used in the orthopedic surgeries using a natural optimization technique called genetic algorithm. Using this method, better values of Performance parameters like rise time, settling time, fall time, peak overshoot and steady state are achieved compared to the conventional PI controller. The SIMUINK MODEL of both the controller operation is obtained using MATLAB version R2013a. The simulated results reveal that the proposed control drive exhibits reduced peak overshoot, rise time, settling time and steady state error. An experimental setup is devised to validate the simulation results. The comparative analysis made depicts the superiority of the proposed algorithm with reference to its conventional counterpart.

Discriminating cosmic muons and X-rays based on rise time using a GEM detector

Gas electron multiplier （GEM） detectors have been used in cosmic muon scattering tomography and neutron imaging over the last decade. In this work, a triple GEM device with an effective readout area of 10 cm × 10 cm is developed, and a method of discriminating between cosmic muons and X-rays based on rise time is tested. The energy resolution of the GEM detector is tested by 55Fe ray source to prove the GEM detector has a good performance. Analysis of the complete signal-cycles allows us to get the rise time and pulse heights. The experiment result indicates that cosmic muons and X-rays can be discriminated with an appropriate rise time threshold.

Research and implementation of 100 A pulsed current source pulse edge compression

In order to increase the usefulness of pulsed current source in engineering practice, research and study was carried out on how to increase the pulse current amplitude, reduce the rise /fall time of output pulse and MOSFET switching losses, etc. Through the analysis of the pulsed current source works theory and the mathematical derivation of the circuit model, the deduction and calculation of the pulse edge compression control methods, and improve the overall circuit structure and optimize the manufacturing process according to the theory. The following indicators was realized： the output pulse current amplitude can be up to 100 A, the shortest pulse rise / fall time was 18.8 ns and 16.1 ns respectively when the maximum amplitude output, the pulse width could be narrowest to 40 ns, repetition frequency could achieve 10 Hz to 10 k Hz, MOSFET switching losses decreased by 30.9 %. This pulsed current source can be used, not only as the power supply for the ordinary high speed narrow pulse width laser diode, but also as an ideal drive power for the high energy, narrow width pulse laser diode.

Study of the effect of switching speed of the a-SiC/c-Si(p)-based,thyristor-like,ultrahigh-speed switches,using two-dimensional simulation techniques

A parametric study for a series of technological and geometrical parameters affecting rise time of Al/aSiC/c-Si（p）/c-Si（n~＋）/Al thyristor-like switches,is presented here for the first time,using two-dimensional simulation techniques.By varying anode current values in simulation procedure we achieved very good agreement between simulation and experimental results for the rising time characteristics of the switch.A series of factors affecting the rising time of the switches are studied here.Two factors among all others studied here,exerting most significant influence,of more than one order of magnitude on the rising time,are a-SiC and c-Si（p） region widths,validating our earlier presented model for device operation.The above widths can be easily varied on device manufacture procedure.We also successfully simulated the rising time characteristics of our earlier presented simulated improved switch,with forward breakover voltage V（BF） = 11 V and forward voltage drop VF = 9.5 V at the ON state,exhibiting an ultra low rise time value of less than 10 ps,which in conjunction with its high anode current density values of 12 A/mm^2 and also cheap and easy fabrication techniques,makes this switch appropriate for ESD protection as well as RF MEMS and NEMS applications.

Thermal analysis for fast thermal-response Si waveguide wrapped by SiN

A new type of Si waveguide wrapped by silicon nitride （SIN） is designed, and its optical and thermal analysis are presented. The thickness of SiN up-cladding should be larger than 1 pm in order to prevent the absorption of optical field by metal heater. Thermal response of the proposed waveguide structure is enhanced by the high thermal conductivity of SiN. Moreover, this thermal response can be further improved by a fast heat dissipation channel created in this structure. Our simula- tion results indicate that a rise time of about 110 ns can be achieved for the proposed waveguide structure, which is about two orders of magnitude less than that of the conventional Si waveguide. The influences of the thickness of up-cladding and the stretching width and etching depth on the thermal performance are also discussed. The simulation shows thin up-cladding, large stretching width and etching depth are critical to enhance the thermal response speed.