Continuity of steered vacuum arc with Al cathode and N₂ flow under pressure of 0.1-5Pa is investigated. Two constant-current power supplies (60V open-circuit voltage/30V load voltage and 310V /240V) and a constant-voltage power supply with open-circuit voltage of 550V are used. Arc current is 30 A, N₂ flow rate is 20ml/min, and transverse magnetic field density at the cathode edge is 1.2mT. The following results are obtained. (1) When the power supply with lower open-circuit and load voltages is used, decrease in pressure causes the arc to lose sustainability. (2) When the power supply with high open-circuit and load voltages is used, the arc can continue even at lower pressure. (3) When the power supply with higher load voltage is used, abnormal discharge behind the magnet field guide-disk may occur at lower pressure.
The above mentioned influence of power supply on arc continuity is interpreted in terms of column fall and generation of a new cathode spot.

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We measured an electric field in transformer oil/pressboard composite insulation system under dc voltage application using Kerr electro-optic measurement system. When a pressboard was inserted between two parallel-plane electrodes, the electric field between the pressboard and the cathode decreased monotonously with time. On the other hand, the electric field between the pressboard and the anode increased with time, reached a maximum value and then fell down. We discussed this phenomenon by charge accumulation model and potential distribution considering the difference in charge accumulation rate on the pressboard between positive and negative charges.
In this paper, discussion results were described based on experiment with pressboards changing its thickness, location and number.

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It is shown in this paper that the electric conduction in transformer oil is significantly affected by the presence of a solid/liquid interface. Using a blade-plane electrode geometry, we investigated the influence of an insulator inserted along the plane of symmetry of an electrode gap on conduction currents in transformer oil. Though the stationary relationship between current I and voltage V always showed the linear plots of V vs. I^1/3, conduction currents were prominently decreased by the presence of the insulator. This reduction of current is discussed on the bases of the electrohydrodynamic (EHD) motion and the electric field of the blade edge taking the insulator surface charging into account.

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The authors have studied on current variation with time for a point-to-plane negative corona discharge in N₂ and N₂/NO mixture. It has been deduced that the variation depends on change of NO concentration by corona discharge. In this study, emission spectra were measured to obtain NO concentration which is estimated by intensity of NO γ band (A² ∑⁺→X²Π). From the results, it is suggested that the NO concentration decreases with time by corona discharge and its change causes variation of current.

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The effect of Si content, grain size and thickness on iron losses in non-oriented electrical steels sheets were investigated. The non-oriented electrical sheets with larger grain sizes have higher permeabilities, lower hysteresis losses and higher eddy current losses. However, the effect of grain size is weaker at higher magnetic fluxes. The ratios of eddy current losses to values due to classical theory increase sharply in thinner non-oriented electrical sheets. The permeabilities and hysteresis losses are little affected by thickness except non-oriented electrical sheets less than 0.2mm thick. The frequency dependences of magnetic properties in non-oriented electrical sheets are estimated from skin effects

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Dc breakdown strength and pulsed breakdown time lag of saturated superfluid liquid helium (HeII) at 1.4K and 1.85K are measured over a wide range of electrode size and applied field strength. The results of the measurements are statistically analyzed by using Weibull distribution functions. It is found that area effect is dominant for do and pulsed breakdown rather than volume effect as in the case of liquid helium of 4.2K (HeI). A shape parameter in the Weibull distribution function for do breakdown strength of HeII is smaller than that of HeI. As a result, do breakdown in superfluid helium can take place in a wider electrode area than in normal liquid helium, while no remarkable difference in breakdown area are observed between 1.85K and 1.4K. On the other hand, the statistical time lag in HeII becomes shorter with temperature decrease. According to Fowler-Nordheim theory, it is suggested that a higher electron mobility in HeII may increase the field emitted electron kinetic energy to trigger the liquid breakdown with a higher probability.

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Behavior of spherical metal particle was observed with high speed camera at the instance of partial discharge inception in oil immersed insulating system. The polarity of metal particle's charge was evaluated by the behavior of the particle and the direction of electric field. The positively charged particle moves to the press-board on negative electrode to initiate partial discharge. The charge quantity of the particle can be calculated by the behavior of particles and electric fields. The movement of particle is so notable on AC peak voltage that partial discharge initiation can be observed on the peak voltage. The mechanisms of partial discharge is proposed.

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Fractals could provide a good description of natural scenes and objects based on their statistically self-similar property. They could also be used to discriminate natural or man-made objects, since natural objects have better fits to the fractional Brownian motion (fBm) model than artificial objects. Sea clutter as natural phenomena will well fit to the fBm to induce little error. On the other hand, targets as man-made objects will induce much more error because they frequently deviate from the fBm model. Therefore, the fractal error could be a good feature to detect targets embedded in clutter.
For an X-band radar image, the fractal error based on spectral density method can enhance the radar targets and suppress the clutter simultaneously. The signal-to-noise ratios of the X-band radar images increase over 10dB. The probability of detection is also increased very high for a desired false alarm rate.
For a millimeter wave (MMW) radar image, we also demonstrate that the fractal error is a better feature than the fractal dimension by observing the feature variation curves of the fractal dimension and fractal error features. The fractal error is used as a feature to classify targets and clutter associated with a wavelet feature extractor and an unsupervised neural classifier. A ship target has successfully been distinguished from sea clutter, and the pattern of the ship is clearly recognized.

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Space charge accumulation phenomena have been widely discussed recently. Many researchers have used the pulsed electroacoustic space charge measuring method to evaluate the dc characteristics of insulating materials, especially those used with high-voltage cables, and their results should be useful for the development of high-voltage dc power apparatus. We have measured the internal space charge behavior of new functional polymers, such as ion conductive antistatic polymers by the method. In this paper, we describe the internal space charge behavior of a charge transport layer (CTL) of an organic photoconductor (OPC) with changing the electrode materials. The experimental results indicate that the hole injection into a CTL from an anode is influenced by the types of electrode materials. The maximum charge quantity was obtained when the Felmi level of an electrode material and that of a CTL.

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A simple structured flow speed sensor in which a polarization maintaining optical fiber is used as a Karman's vortex generator and also a vortex frequency sensor had been proposed. For measuring ocean current velocity, a double fine type sensor mount was designed and investigated in detail experimentally.Even if the experimental results showed its essential effectiveness, several problems were also found out.
A conduit type sensor mount has newly been proposed for solving these problems. A sensor for this mount has been constructed by using a 16^φ circular pipe. Experimental results of the sensor shows a wide range agreement between detected frequencies vs, measured flow speeds and the expected frequencies with Roshko's equation. And the minimum detectable flow speed of 0.27m/s is obtained.

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In a multilayer insulator made of two or more materials with different dielectric constants and conductivities, internal space charge accumulates at their interfaces. If the local field is increased by the accumulated charge, the electric durability of the insulator should be decreased. In this paper, we describe the space charge accumulation measured when using oil-impregnated PPLP (polypropylene laminated paper)-which consists triple layers; kraft paper, polypropylene (PP), kraft paper-was subjected to a strong dc electric field. The experimental results suggest that internal space charge accumulates at both surfaces of a PP layer and that the electric field in the kraft paper layers disappears.

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The electron density-dependence of effective diffusion coefficient D_s for electrons in argon Maxwellianized plasmas has been verified experimentally by means of afterglow technique. A calibrated microwave resonant cavity was used for measuring the electron density. By appending a synchronous detector to a conventional circuit, the sensitivity for the electron density <n_e> averaged over the volume of the cavity increased by about three orders of magnitude. Temporal behavior of the electron density between 1016 and 2.5×10¹¹ m^-3 at pressures of 46.6 and 66.5Pa was measured. In order to compare the experimental with theoretical results, <n_e> was transformed into the axial dcnsity, by the decay rate of which D_s was determined. The values of D_s were compared with those obtained theoretically by several authors in the range of ratios between 4 and 500 of the characteristic diffusion length Λ of the discharge tube to the Debye length λ_D0 for electrons. It was found experimentally that diffusion mode changed from ambipolar diffusion to transition modes when Λ/λ_D0 became smaller than about 100.

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Process in polymer free volume is very important in initiation phase of electrical tree under ac stress. Electrons injected from electrode are accelerated in free volume (10-100nm) and bombard free volume wall to produce free radical and break polymer chain. Kind of gas in free volume has a large effect on ac tree initiation Under O₂ rich condition, free radicals react with O₂ and autoxidation process starts. Autoxidation, chain reaction with low activation energy, creates large cavity in short time, where discharge can occur.He or Ar atoms in free volume are excited to metastable level by electron impact Metastable atoms collide with free volume wall and break polymer bond with high efficiency, and creates cavity in short time.

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Analog Indicating Electrical Instruments were developed in the last half of the nineteenth century. Having searched for the source of precision readings in the measuring such as astrolabes, Tyco's quadrant or surveyng instruments which employed nonious scales, diagonal scales and micrometer driven scales in Europe, the US and Japan from the fourteenth century, the author found that Edward Weston in the US employed diagonal scales for the precision electrical meters.
Through the reproduction of old hand-drawing method of Electrical Instruments Scales which have diagonal graduations, he concluded that the diagonal scales were the most appropriate measure for precision analog electrical meters.

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A new evaluation technique for the centroid drift velocity W_r of isolated electron swarms in gases is proposed based on moment equations. In addition to the average velocity W_v of the individual electrons in an electron swam, W_r has another velocity componemt due to effects of ionization and eleotron attachment. Mechanisms that cause the difference between W_r and W_v are illustrated, and quantitatively demonstrated by simulations using a propagator method. The effects of ionization and electron attachment on W_r are analyzed in detail by introducing the moment generation rate as a key quantity to categorize the effects.

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Because of the excellent electrical insulation performance of low density polyethylene (LDPE), it can be expected that minute amount of ionic impurities in LDPE, which is difficult to detect by general analytlcal methods, has an influence on DC characteristlcs such as conductivity and space charge formation. As the above-mentioned, two kinds of LDPE samples (sample A, sample B), in which no difference was appreciated by a general analysis, were supplied, and were examined by the measurement of dielectric loss (tanδ), conductlvity and space charge formlation (by the pulsed electro acoustic method) over the temperature range of R-90°C and the electrical stress range of 10-30kV/mm.
A greater conductivity in sample B was thought to be attributable to the minute amount of ionlc impurities, which was confirmed by the tanδ results measured under higher temperature and electrical stress. However, the hetero space charge formation in sample B (with greater ionic impurities) was smaller than that in sample A. Accordingly, it is considered that sample B exhibits a larger cancellation in space charge formation, because the space charge is formed by the total of inner ionic carriers (hetero charge) and injected carders from the electrode (homo charge) and both carriers are affected by impurities.

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Eddy Current Testing (ECT) is one of the non-destructive testing methods using electromagnetic phenomena and an effective method for detecting cracks or flaws in conducting materials. ECT can detect internal small cracks in non-ferromagnetic heat exchanger tubes on petroleum plants. In this case differential type probe coils are usually used for inspection of the tubes and defects can be detected as a probe impedance trajectory by moving the coils inside the tube. And higher frequency in this method is needed for the purpose of detecting very small surface cracks in tubes. But it is difficult to test thick ferromagnetic steel tubes using the conventional ECT method. Because test signals of the steel tubes include magnetic noises caused by distribution of initial permeability. Therefore we studied to control the initial permeability and to reduce the magnetic noise using a permanent magnet which magnetize the steel tube on region of less than magnetic saturation point. This ECT probe is differential coils type wound around a columnar permanent magnet. We purposed to make its phenomenon clear by numerical analysis using axisymmetric FEM.

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This paper describes research on the formation and decay processes of interfacial interfacial charge in PE/EVA laminates. At the interface between PE and EVA, charge of the order of 10-100μC/m² accumulated when a D.C. voltage of up to 15kV (30kV/mm) was applied to PE/EVA laminates. The interfacial charge decreases exponentially with at least two time constants and depends on the polarity of the applied voltage. For the case of PE/EVA (VA=19wt%), one time constant is in the range of 1.2-1.7 [hrs] and the other is in the range of 3.9-9.5 [hrs]; these constants are of the same orderas those for single sheet EVA and LDPE, respectively. As the amount of VA in EVA increased, the first time constant was found to decrease more rapidly. Increasing the amount of VA in EVA increased the electric conductivity of the EVA and the charge in the EVA side but decreased the time coustant for decay in the EVA. The decay time constant was found to be proportional to abort 0.4 power of dielectric relaxation time.

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