Discharge Current Value Research Articles

카네이션 생산성 향상을 위한 펄스 전원을 활용한 방전관형 오존발생기의 특성

본 논문은 카네이션의 생산성 향상을 위하여, 펄스 전원을 활용한 소형 저비용 방전관형 오존발생기를 설계ㆍ제작하였다. 펄스 전원의 출력전압, 원료 가스인 모의공기의 유량과 오존발생기의 작동 개수에 따른 방전관형 오존발생기의 방전 및 오존생성특성을 연구 검토하였다. 방전관형 오존발생기의 방전전압 및 전류는 펄스 전원의 출력전압에 비례하였다. 방전관형 오존발생기의 오존생성농도 및 오존발생량은 펄스 전원의 출력전압 및 오존발생기의 작동 개수에 비례하였다. 방전관형 오존발생기의 최대 오존생성농도 및 오존발생량으로 각각 890[ppm] 및 59.7[㎎/h]를 얻을 수 있었다. 방전관형 오존발생기를 카네이션 재배 하우스에 사용하였을 때, 카네이션 꽃대 길이와 굵기가 균일하여 품질 향상과 대기ㆍ토질 개선을 통한 카네이션 생산성 향상의 효과를 얻을 수 있었다.

Time-resolved probe diagnostics of pulsed DC magnetron discharge during deposition of TiOx layers

The paper presents an experimental study of a pulsed DC unbalanced magnetron discharge with Ti target. This system is being used for deposition of nanocrystalline TiOx thin films. The unbalanced magnetron was operated in pulsed regime with the low repetition frequency of modulation cycle νp=250 Hz and relatively short active part of modulation cycle Ta=150 μs. Low average discharge current was used with maximum value about 1 A. Maximum instant discharge current in the active part of modulation cycle was 20 A. Relatively high plasma density up to value ne≈1018 m−3 was achieved at these conditions but due the low average power absorbed in the plasma the heat load applied on the target and the substrate was low. Time-resolved and spatially resolved Langmuir probe diagnostics was used for the systematic and detailed experimental study of the system. Experimental conditions as the instant value of discharge current, gas pressure in the reactor, gas mixture ratio Ar/O2, etc. were varied in a broad range. The time evolutions of plasma parameters such as electron density, electron temperature, plasma potential and EEPF were determined during the modulation cycle of pulse discharge excitation.

Multi-objective optimisation of high-speed electrical discharge machining process using a Taguchi fuzzy-based approach

The paper describes the application of the fuzzy logic analysis coupled with Taguchi methods to optimise the precision and accuracy of the high-speed electrical discharge machining (EDM) process. A fuzzy logic system is used to investigate relationships between the machining precision and accuracy for determining the efficiency of each parameter design of the Taguchi dynamic experiments. From the fuzzy inference process, the optimal process conditions for the high-speed EDM process can be easily determined as A 1B 1C 3D 1E 3F 3G 1H 3. In addition, the analysis of variance (ANOVA) is also employed to identify factor B (pulse time), C (duty cycle), and D (peak value of discharge current) as the most important parameters, which account for about 81.5% of the variance. The factors E (powder concentration) and H (powder size) are found to have relatively weaker impacts on the process design of the high-speed EDM. Furthermore, a confirmation experiment of the optimal process shows that the targeted multiple performance characteristics are significantly improved to achieve more desirable levels.

Statistical analysis of lightning performance of distribution lines based on observation in fields

AbstractBecause of the lower insulation level than for transmission lines, in this study on lightning protection design of distribution lines, not only direct lightning strokes but also induced voltages caused by nearby strokes must be taken into account. Thus, it is necessary to grasp the frequency of occurrence of lightning phenomena around distribution lines. For this aim, lightning phenomena on TEPCO's distribution lines in use were continuously observed for 6 years (1996 to 2001). Through this observation, new interesting statistical data that can be a useful basis for rationalization of lightning protection design of distribution lines were obtained. Two hundred and four lightning strokes were observed through the six‐year period. Probability of occurrence of a direct stroke was 22% (45 direct strokes were obtained). The fact that in 47% of direct strokes the electric outage did not occur is very interesting. Moreover, the value of surge discharge current of the arrester in the case of nearby stroke is the basis for conventional theory of grounding system. Therefore, statistical analysis of ZnO discharging current in the case of nearby strokes was carried out. As a result, in the case of nearby strokes, 5% value of cumulative frequency of discharging current is 0.5 kA. This value is half the conventional data. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(2): 8–16, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20180

Statistical Analysis of Lightning Performance of Distribution Lines Based on Observation in Fields

Because of the lower insulation level than is for transmission line, in this study on lightning protection design of distribution line, not only direct lightning strokes but also induced voltages caused by nearby strokes must be taken into account. So it is necessary to grasp the frequency of occurrence on lightning phenomena around distribution lines. For this aim, lightning phenomena on TEPCO’s distribution lines in use had been continuously observed for 6 years (1996-2001). Through this observation, new interesting statistical data, that can be useful basis for rationalization of lightning protection design of distribution lines was obtained. 204 lightning was observed through six years observation in all. Probability of occurrence of direct stroke was 22% (45 data of direct stroke was obtained). The fact that in 47% case of direct stroke the electric outage didn’t occur is very interesting. Moreover, the value of surge discharge current of arrester in case of nearby stroke is basis for conventional theory of grounding system. Therefore statistical analysis of ZnO discharging current in case of nearby strokes was carried out. As a result, in case of nearby strokes, 5% value of cumulative frequency of discharging current is 0.5kA. This value is half of conventional data.

Wall material effects in stationary plasma thrusters. II. Near-wall and in-wall conductivity

Simulations and experimental characterizations of a stationary plasma thruster are compared for four different wall materials to investigate near-wall conductivity (dielectric materials) and in-wall conductivity (conducting materials) in such a discharge. Using a one-dimensional transient fluid model that takes into account a possible electron temperature anisotropy, it is shown that electron-wall backscattering plays a crucial role by maintaining a relatively high electron temperature along the magnetic field lines which in turn drives large electron currents toward the walls. The large differences in discharge current observed experimentally for the dielectric materials are qualitatively recovered, confirming that near-wall conductivity results from the combined effects of secondary electron emission and electron backscattering. A clear correlation is found between the appearance of space charge saturation at the walls and a jump of the discharge current observed in experiments when varying the discharge voltage or the magnetic field. The anomalously high values of discharge current observed experimentally with graphite are also correctly recovered in simulations, which highlight a plasma short-circuiting effect resulting from in-wall currents.

Impedance Control of Reactive Sputtering Process in Mid-Frequency Mode with Dual Cathodes to Deposit Al-Doped ZnO Films

Aluminum-doped zinc oxide (AZO) films were deposited on glass substrates at 300°C by reactive mid-frequency (mf, 50 kHz) magnetron sputtering using dual magnetron cathodes with aluminum–zinc alloy targets. In order to keep the very high deposition rate stable in the transition region of the reactive sputtering system, the reactive gas (O2) flow was controlled using the “discharge impedance feedback system”, where the discharge current value was used to control the O2 flow. The highest deposition rate for the transparent conductive AZO films achieved by this dual magnetron sputtering (DMS) system was 242 nm/min, which was higher by one order of magnitude than that achieved by the conventional reactive sputtering system. The lowest resistivity of the AZO film obtained by such a high deposition rate was 4.4×10-4 Ωcm. The structure and electrical properties of the films varied systematically by controlling the discharge current in the transition region using this system.

Second derivative Langmuir probe measurements of negative oxygen ionconcentration taking into account the plasma depletion caused by negative ionsink on the probe surface

Taking into account the effect of plasma depletion caused bynegative ion sink on the probe surface, a refinement of the second derivativeLangmuir probe method for the determination of negative ion concentration isproposed. The concentration of the negative ions is obtained by comparing theexperimental data with the calculated second derivative probe current signalsat a finite ratio of probe radius and negative ion free path.In a specially constructed dc discharge tube with coaxial electrodes, secondderivative Langmuir probe measurements are performed in pure oxygen (gaspressure 30-110 Pa, discharge current 40-80 mA). The negative ionconcentrations at different discharge current and gas pressure values areobtained. The factors affecting the uncertainties of the results arediscussed.The values of the negative oxygen ion concentration obtained by laserphotodetachment measurement are in good agreement with those obtained by thesecond derivative Langmuir probe measurements.The proposed processing of the experimental data extends the applicability ofthe second derivative Langmuir probe method for accurate measurements of thenegative ion concentration at higher gas pressures and finite probe radii.

単発放電による微細電極の瞬時成形 １ 先端微細化現象と成形電極の応用

Recently, electrical discharge machining (EDM) has been applied to micro processing. A thin electrode less than 0.1 mm in diameter has been used for the micro EDM. In conventional micro EDM, minute energy is supplied to the gap region for micro removal machining. In this study, we carried out some experiments on single discharge machining with thin electrode. The value of discharge current was selected up to 50A as the machining condition. The electrode wear length was measured for several pulse durations. As a result, we found out the electrode became thinner than original diameters at the edge portion under pulse duration of several hundred μs in a single discharge. A needle of 35μm in diameter and 300μm length can be made instantaneously from a tungsten wire of 0.125mm in diameter. Using a thin electrode, micro drilling could be performed on the machine. The rapid thin electrode production mechanisms are discussed taking into consideration of electromagnetic force, electrostatic force and plasma jets flow.

Analysis of electro-discharge machining process and its comparison with experiments

A theoretical model to estimate the material removal rate and surface quality of the workpiece has been developed. The model provides equations to calculate the workpiece material removal rate and maximum peak-to-valley height of the workpiece surface finish. Experiments with different values of discharge current, pulse duration time and interval time were conducted to investigate their effects on the surface finish of the workpiece and material removal rates. The theoretical prediction and experimental results are in agreement when compared.

111 単発放電による微細電極の瞬時成形とその応用

Recently, electrical discharge machining (EDM) has been applied to micro processing. A thin electrode less than 0.1mm in diameter has been used for the micro EDM. In conventional micro EDM, minute energy is supplied to the gap region for micro removal machining. In this study, we carried out some experiments on single discharge machining with thin electrode. The value of discharge current was selected up to 50A as the machining condition. The electrode wear length was measured for several pulse durations. As a result, we found out the electrode became thinner than original diameters at the edge portion under pulse duration of several hundred μs in a single discharge. A needle of 35μm in diameter and 300μm length can be made instantaneously from a tungsten wire of 0.125mm in diameter. Using a thin electrode, micro drilling could be performed on the machine.

Parametric study into erosion wear in a computer numerical controlled electro-discharge machining process

Experiments with different values of discharge current, pulse duration time and interval time in electro-discharge machining were conducted to investigate their effects on the material removal rate, surface quality and dimensional accuracy of the tool and product. Optimum pulse duration and pulse interval values in EDM that either produce the highest erosion rate or fine surface finish have been shown to have significant importance to the machining process.

Temperature measurements in oxygen negative glow using a synthetic low-resolution spectrum

The measurement of the neutral temperature axial profile of an oxygen negative glow is presented. It uses a comparison between synthesised and experimental low-resolution spectra of the first negative system of nitrogen, present as an impurity in the gas. The temperature is shown to reach 1100 K near the cathode for the highest values of discharge pressure and current.

放電加工における加工面変質層の観測

Heat generated by the repeating pulse discharge in EDM affects the surface of workpiece. This heat effect depends on the wave form of the pulse discharge in EDM, for example, peak value of pulse discharge current, pulse duration, duty factor, and so on.This paper describes the relation between the electrical condition of wave form and the depth of heat effected layer of workpiece. We present fundamental data for determination of the optimum electrical condition in EDM.We think of the radius of virtual thermal source on producing micro craters by pulse discharge. The radius is derived with due regard to the expansion of arc channel. The depth of transformed layer is calculated from the radius, and is about the same value obtained from the microvickers hardness of workpiece. And we show that the radius can be calculated from the peak value of pulse discharge current and pulse duration, so the depth of heat effected layer can be estimated.

Study of the decomposition of wet SF6, subjected to 50-Hz ac corona discharges

Mixtures of SF6 (100 kPa≤PSF6≤400 kPa) and water (concentrations ranging from 240 to 2000 vpm) have been submitted to point-plane 50-Hz ac corona discharges. The only stable gaseous by-products detected, either by gas-phase chromatography or gas chromatography–mass spectrometry techniques, were SOF2 and SO2F2. The variation of their concentrations as a function of the discharge current value (3–25 μA rms), the charge transported (0.15–1.5 C), the water content, the SF6 pressure, and the gap spacing (1.5–5 mm) have been studied. The results indicate that, at least in our experimental conditions, the 50-Hz ac corona discharges behave more like negative than like positive dc corona.

Polymer film formation in C2F6H2 discharges

Abstract Thin fluoropolymer films deposited in an r.f. discharge fed with C 2 F 6 H 2 mixtures were studied. The effect of the electrical characteristics, the substrate temperature and the feed composition on both the chemical structure of the film and on the growth mechanism were analysed. It was found, in particular, that the structure of the film is affected by the H 2 concentration in the feed and by the discharge voltage and current values and that the polymerization rate decreases with temperature after a threshold.

Population of excited He states (3≤n≤) by dielectronicHe+recombination in dc hollow-cathode discharge

The contribution of dielectronic recombination to the population of radiative He I states (3< or =n< or =8) in a He dc hollow-cathode discharge of 4-cm length and 2-cm diameter is determined in the discharge pressure range 0.6--4.0 Torr and at discharge current values of 10, 13, 16, 19, 22, and 25 mA by radial sampling of the emitted line radiation and the ion densities. In addition, the afterglow phase of the same discharge is explored as to the radial and time dependence of line radiation intensity and ion density. In the active phase at low density (2 Torr) and at higher pressure but at too low a discharge current (below 12 mA) all the radiation is due to electron impact excitation of the He states. Only at a pressure of about 4 Torr and a discharge current above 20 mA does recombination play a significant role in populating radiative He I states on the axis of the discharge. The radial dependence of the He II radiation shows the geometric density increase of the very fast unscattered electrons having the full sheath energy. Both results are relevant for hollow-cathode-laser development.

Theory of electrochemical hydrogen evolution reactions: Part I. The model and fundamental relationships

A model of electrochemical hydrogen ion discharge and hydrogen desorption processes (reactions I and II, respectively) is developed which combines the principal features of the Marcus-Levich-Dogonadze theory of electron transfer in a polar medium and the theory of electron transfer into reaction complex applied by Gurney, Butler and Bockris to reaction (I). The present model is based on the following underlying assumptions: (1) reactions (I) and (II) are reactions of electron tunnelling from metal to reaction complex, the tunnelling length exceeding the Helmholtz layer thickness; (2) the final transition state term is, due to instability of the H 3O radical, a decay term and at large H-OH 2 distances becomes a final product term (H ads and H 2 in reactions I and II, respectively), so that an electronic transition involves spontaneous hydrogen atom abstraction from H 3O. It is shown that within this model the effect of solvent reorganization on reaction rate is determined by the final state term slope F, since the vertical transition energy is divided between the reaction coordinate and degrees of freedom of the solvent in the ratio: ζ= F 2 δ 2/2 E p kT ( δ is the initial state zero-point energy; E p is the reorganization energy). Due to the different F in reactions (I) and (II) (20 eV nm −1 and 50 eV nm −1 respectively), the first one is dominated by the solvent reorganization and the second by transition along the reaction coordinate. In the region of normal H 3O + discharge according to reaction (I) transition probability w obeys the Tafel law and, since the transition along the reaction coordinate is considered, the transfer coefficient is constant (0.5±0.05) when w varies within 13–14 orders of magnitude at realistic E p values (1.5 to 2.0 eV) and discharge current values consistent with the experiment. In the same potential range, reaction (II) is activationless, but the exponential dependence of w upon φ is preserved because the barrier height changes with the potential φ. Coefficient b in the Tafel equation is a linear function of temperature, and Conway's treatment of the experimental results has shown it to equal: b= b 1 kT+b 2, with b 2/ b 1 kT=ζ

Berechnung und experimenteller Vergleich des Verst�rkungsfaktors f�r den Laser�bergang 6328 � in einer He-Ne-Gasentladung

Rate equations for the density of excited atoms in a He-Ne discharge are solved for the steady state. The atomistic parameters in the theoretical treatment are replaced by experimental values. Hence inversion density and single pass gain can be calculated as a function of gas mixture, pressure, discharge current and the geometry of the discharge tube. Conditions for maximum inversion density and single pass gain were calculated and compared with experimentally determined values. Good agreement was found for the maximum single pass gain and the related values of discharge current, gas mixture and pressure.