ELECTRICAL IMPEDANCE OF ELECTRODES IMMERSED IN MOVING PLASMA

1963 ◽  
Vol 41 (8) ◽  
pp. 1346-1358 ◽  
Author(s):  
P. R. Smy
Keyword(s):  
Electric Fields ◽  
Electrical Impedance ◽  
Debye Length ◽  
Argon Plasma ◽  
Initial Pressure ◽  
Electrode Impedance ◽  
Experimental Conditions ◽  
Order Of Magnitude ◽  
Moving Plasma ◽  
Displacement Currents

The electrical impedance of two cold electrodes immersed in moving argon plasma has been measured. The plasma is formed by a shock wave moving at 4–8 × 105 cm/sec into argon at an initial pressure of 0.01–1 mm Hg. It is found that a pronounced discontinuity in electrode impedance exists under all experimental conditions at electrode voltages in the neighborhood of 50 volts. An appreciable capacitance, which is dependent both on electrode area and on plasma density, is detected in the electrode impedance with electrode voltages of less than about 50 volts. This is ascribed to displacement currents in a sheath at the surface of one or both electrodes. Values of sheath thickness calculated from the observed "capacities" show order-of-magnitude agreement with the calculated plasma Debye length. Since the sheath electric fields corresponding to an electrode voltage of 50 volts and these sheath thicknesses are in the range 106–108 volts/cm, it is thought that the observed impedance discontinuity arises from the onset of electron emission from the cathode.

Two-Temperature Model for the Simulation of Atmospheric-Pressure Helium ICPs

1995 ◽  
Vol 49 (10) ◽  
pp. 1390-1402 ◽  
Author(s):  
Mingxiang Cai ◽  
Akbar Montaser ◽  
Javad Mostaghimi
Keyword(s):  
Electric Fields ◽  
Gas Flow ◽  
Heavy Particle ◽  
Argon Plasma ◽  
Input Power ◽  
Temperature Model ◽  
Inductively Coupled ◽  
Order Of Magnitude ◽  
Coupled Plasmas ◽  
Two Temperature

A two-temperature model (2-T model) was used to predict fundamental properties of pure helium inductively coupled plasmas (He ICPs). Plasma characteristics with the use of the 2-T model were compared to those obtained by the local thermodynamic equilibrum (LTE) model for the He ICP, to those of an Ar ICP, and to the existing experimental data. The distributions of electron and heavy-particle temperatures, electron number density, and electric and magnetic fields were obtained as a function of the internal diameters of the torch, the gas flow rates, the gap between the plasma tube and the MACOR insert, the generator frequency, and the active power. Overall, the He ICP was predicted to have a much higher electron temperature (> 12,000 K) in the load coil region, but its axial heavy-particle and electron temperatures (∼2000 K) at the analytical zone were lower than those of the Ar ICP (4000–6000 K). The high-temperature region in the He ICP was constricted to a smaller region close to the wall of the plasma confinement tube as compared to that in the Ar ICP. Most of the input power in the He ICP was lost through the plasma quartz tube. The magnetic and electric fields inside the induction coil in the helium plasma were approximately one order of magnitude higher than those in the argon plasma.

Sheath-Convection Effects with Flush-Mounted Electrostatic Probes

1971 ◽  
Vol 49 (20) ◽  
pp. 2540-2546 ◽  
Author(s):  
R. M. Clements ◽  
P. R. Smy
Keyword(s):  
Electron Density ◽  
Free Stream ◽  
Diffusion Theory ◽  
Debye Length ◽  
Leading Edge ◽  
Plasma Electron ◽  
Electronic Charge ◽  
Order Of Magnitude ◽  
Moving Plasma ◽  
Cooling Effects

Theoretical expressions are derived for the ion current to a planar flush-mounted probe which arises from the convection of ions from a moving plasma into the probe sheath. The two situations considered are those where the sheath is either very large or is small compared with the boundary layer. It is found that sheath effects, with an accompanying lack of true current saturation with increasing probe bias, can be expected to intrude when the parameter REα2χ2 > (X/l)1/4. (RE = electric Reynold's number, α = ratio of Debye length to probe length [X], χ = potential of probe normalized with respect to the electron energy, and l = the distance of the probe from the leading edge of the surface into which it is mounted.) For values of REα2χ2(l/X)2 which exceed unity, the formula[Formula: see text](where ne = plasma electron density, u∞ = free stream flow velocity, V = probe bias, μ∞ = free stream ion mobility, e = electronic charge, and ε0 = permittivity of free space) is derived. At lower values of REα2χ2(l/X)2 theoretical considerations which take compression and cooling effects into account show that the above relation should still be approximately correct down to values of [Formula: see text]. The relation shows good agreement with the recent results presented by Scharfman and Bredfeldt under conditions where they report the conventional diffusion theory to be in error by up to one order of magnitude, and moreover to predict an incorrect variation of current with electron density and probe bias.

scholarly journals Ionic transport through a protein nanopore: a Coarse-Grained Molecular Dynamics Study

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Nathalie Basdevant ◽  
Delphine Dessaux ◽  
Rosa Ramirez
Keyword(s):  
Molecular Dynamics ◽  
Lipid Bilayer ◽  
Electric Fields ◽  
Ionic Transport ◽  
Stationary Regime ◽  
Coarse Grained ◽  
Experimental Conditions ◽  
Current Saturation ◽  
Order Of Magnitude ◽  
Dynamics Simulations

Abstract The MARTINI coarse-grained (CG) force field is used to test the ability of CG models to simulate ionic transport through protein nanopores. The ionic conductivity of CG ions in solution was computed and compared with experimental results. Next, we studied the electrostatic behavior of a solvated CG lipid bilayer in salt solution under an external electric field. We showed this approach correctly describes the experimental conditions under a potential bias. Finally, we performed CG molecular dynamics simulations of the ionic transport through a protein nanopore (α-hemolysin) inserted in a lipid bilayer, under different electric fields, for 2–3 microseconds. The resulting I − V curve is qualitatively consistent with experiments, although the computed current is one order of magnitude smaller. Current saturation was observed for potential biases over ±350 mV. We also discuss the time to reach a stationary regime and the role of the protein flexibility in our CG simulations.

The Numerical Modeling of Spherical Explosion in the Foam

2016 ◽  
Vol 11 (1) ◽  
pp. 60-65 ◽  
Author(s):  
R.Kh. Bolotnova ◽  
E.F. Gainullina
Keyword(s):  
Shock Wave ◽  
Numerical Modeling ◽  
Initial Pressure ◽  
Water Volume ◽  
Symmetric Model ◽  
Two Phase ◽  
Experimental Conditions ◽  
Initial Water ◽  
Aqueous Foam ◽  
Spherical Explosion

The spherical explosion propagation process in aqueous foam with the initial water volume content α10=0.0083 corresponding to the experimental conditions is analyzed numerically. The solution method is based on the one-dimensional two-temperature spherically symmetric model for two-phase gas-liquid mixture. The numerical simulation is built by the shock capturing method and movable Lagrangian grids. The amplitude and the width of the initial pressure pulse are found from the amount of experimental explosive energy. The numerical modeling results are compared to the real experiment. It’s shown, that the foam compression in the shock wave leads to the significant decrease in velocity and in amplitude of the shock wave.

scholarly journals Numerical and experimental study on turbulence statistics in a large fan-stirred combustion vessel

2021 ◽  
Vol 62 (5) ◽  
Author(s):  
M. E. Morsy ◽  
J. Yang
Keyword(s):  
Isotropic Turbulence ◽  
Burning Velocity ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Initial Pressure ◽  
Dynamics Modeling ◽  
Turbulence Statistics ◽  
Experimental Conditions ◽  
Measured Velocity

Abstract Particle image velocimetry (PIV) has become a popular non-intrusive tool for measuring various types of flows. However, when measuring three-dimensional flows with two-dimensional (2D) PIV, there are some uncertainties in the measured velocity field due to out-of-plane motion, which might alter turbulence statistics and distort the overall flow characteristics. In the present study, three different turbulence models are employed and compared. Mean and fluctuating fields obtained by three-dimensional computational fluid dynamics modeling are compared to experimental data. Turbulence statistics such as integral length scale, Taylor microscale, Kolmogorov scale, turbulence kinetic energy, dissipation rate, and velocity correlations are calculated at different experimental conditions (i.e., pressure, temperature, fan speed, etc.). A reasonably isotropic and homogeneous turbulence with large turbulence intensities is achieved in the central region extending to almost 45 mm radius. This radius decreases with increasing the initial pressure. The influence of the third dimension velocity component on the measured characteristics is negligible. This is a result of the axisymmetric features of the flow pattern in the current vessel. The results prove that the present vessel can be conveniently adopted for several turbulent combustion studies including mainly the determination of turbulent burning velocity for gaseous premixed flames in nearly homogeneous isotropic turbulence. Graphic abstract

scholarly journals Benthic microalgae community response to flooding in a tropical salt flat

2016 ◽  
Vol 76 (3) ◽  
pp. 577-582 ◽  
Author(s):  
L. S. M. Masuda ◽  
A. Enrich-Prast
Keyword(s):  
Sea Water ◽  
Shannon Index ◽  
Community Response ◽  
Microbial Mat ◽  
Total Density ◽  
Experimental Conditions ◽  
Effect Of Water ◽  
Salt Flat ◽  
Field Samples ◽  
Order Of Magnitude

Abstract This research evaluated the effect of flooding on the microphytobenthos community structure in a microbial mat from a tropical salt flat. Field samples were collected during four consecutive days: on the first three days the salt flat was dry, on the fourth day it was flooded by rain. In order to evaluate the community maintained in flood conditions, samples from this area were collected and kept in the laboratory for 10 days with sea water. The results of total abundance of microphytobenthos varied from 4.2 × 108 to 2.9 × 109 organisms L–1, total density increased one order of magnitude under the effect of water for both situations of precipitation in the salt flat and in experimental conditions, an increase due to the high abundance of Microcoleus spp. Shannon index (H’) was higher during the desiccation period. Our data suggest that changes in the abundance of organisms were due to the effect of water. The dominance of the most abundant taxa remained the same under conditions of desiccation and influence of water, and there is probably a consortium of microorganisms in the microbial mat that helps to maintain these dominances.

scholarly journals Large-area printing of ferroelectric surface and super-domains for efficient solar water splitting

2020 ◽  
Author(s):  
Yu Tian ◽  
Yaqing Wei ◽  
Minghui Pei ◽  
Rongrong Cao ◽  
Zhenao Gu ◽  
...  
Keyword(s):  
Water Splitting ◽  
Electric Fields ◽  
Electronic Structures ◽  
Active Sites ◽  
Large Area ◽  
Solar Water Splitting ◽  
High Efficient ◽  
Catalytic Sites ◽  
Order Of Magnitude ◽  
Magnitude Increase

Abstract Surface electronic structures of the photoelectrodes determine the activity and efficiency of the photoelectrochemical water splitting, but the controls of their surface structures and interfacial chemical reactions remain challenging. Here, we use ferroelectric BiFeO3 as a model system to demonstrate an efficient and controllable water splitting reaction by large-area constructing the hydroxyls-bonded surface. The up-shift of band edge positions at this surface enables and enhances the interfacial holes and electrons transfer through the hydroxyl-active-sites, leading to simultaneously enhanced oxygen and hydrogen evolutions. Furthermore, printing of ferroelectric super-domains with microscale checkboard up/down electric fields separates the distribution of reduction/oxidation catalytic sites, enhancing the charge separation and giving rise to an order of magnitude increase of the photocurrent. This large-area printable ferroelectric surface and super-domains offer an alternative platform for controllable and high-efficient photocatalysis.

scholarly journals Research on Key Technology of Electrochemical Sterilization and Physical Application for Circulating Cooling Water

2021 ◽  
Vol 2083 (2) ◽  
pp. 022068
Author(s):  
Xiaohui Wang ◽  
Chunyan Song ◽  
Xueying Xie ◽  
Nan Zhang ◽  
Ruiqing Guo ◽  
...  
Keyword(s):  
Electric Fields ◽  
Electrode Materials ◽  
High Efficiency ◽  
Thermal Power ◽  
Cooling Water ◽  
Environmentally Friendly ◽  
Research Progress ◽  
Electrode Spacing ◽  
Experimental Conditions ◽  
Circulating Cooling Water

Abstract As a high-efficiency, low-cost, convenient and environmentally friendly sterilization technology, electrochemical disinfection has developed rapidly in recent years. Electrochemical sterilization is an environmentally friendly sterilization technology. The research progress of this technology in the recent 30 years in sterilization mechanism and electrode materials is summarized. The mechanism of electrochemical sterilization includes the chemical effects of active chlorine, active intermediates, copper or silver ions, and the physical effects of electric fields; the electrode materials used are titanium anode, carbon cathode, and anode. The article combined with electrochemical equipment in a thermal power plant cold open circulating cooling water treatment experiment. Experimental research found that under the conditions of current density of 120A/m2, residence time of 10s, and electrode spacing of 1.8cm, the bactericidal effect can reach 97%. Under certain experimental conditions and a certain period of time, the total number of heterogeneous bacteria in the circulating cooling water after treatment can be effectively inhibited.

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