In estimating the iron loss of motor cores, it is important to grasp the magnetic properties of electrical steel sheets under applied stress and arbitrary flux conditions. We developed the apparatus to measure 2-D magnetic properties (properties under the arbitrary alternating and rotating flux conditions) of an electrical steel sheet in applying compressive stress normal to the surface. This paper describes the measured iron loss results of the electrical steel sheets with different grades under compressive stress normal to the surface, by using our developed apparatus. According to the measured results, it can be confirmed that the electrical steel sheet with low grade, whose iron loss is bigger, has a possibility to improve its iron loss by applying compressive stress normal to the surface.

This paper describes the electric charge accumulation properties in package insulation layer of power electronic devices (IGBT module and diode bridge) under conditions of DC voltage application (100 V to 4000 V) and temperature conditions (room temperature to 80℃) by using a direct current integrated charge method (DCIC-Q(t)). The DCIC-Q(t) equipment is connected in series to the sample under DC voltage source. The DCIC-Q(t) is contained all information of charging currents to the test sample under applied rectangular wave voltage, such as the integrated charge of initial current, Q₀-=C_sV_dc, the integrated charge of absorption current, Q_abs, and the integrated charge of leakage current, Q_leak. We discuss the charge accumulation properties from Q(t) and the ratio of Q(t)/Q₀ in the electronic devices under various DC voltage and temperatures. The DCIC-Q(t) equipment is useful to evaluate the electric charge accumulation properties in completed power electronic devices.

This paper presents an experimental study on water treatment by electrospray and plasma discharge from a syringe needle. Our aim is to improve the activity of the plasma-chemical reactions in the fog produced by the electrospray. In this study, we propose a pulsed power technique to allow alternating expansions streamer corona discharges and fine water droplets with an alternating frequency of the order of 10² Hz. Under a dc voltage without any ripples, it is difficult to achieve the alternating expansions of the streamer corona and the water droplets. For the successful control of the alternating expansions, an impulse voltage consisting of δ-function-like front and long exponential tail are repeatedly superimposed onto the dc voltage. The discharge light signals detected by a photomultiplier indicate that the streamer propagation is caused by the δ-function component of the superimposed impulse. High-speed photographic observations of the water droplets show that the streamer discharge is followed by the water spray expansions produced by the long tail component of the superimposed impulse. The long tail component has a very important role to deform a large water droplet on the needle tip from the hemispherical shape into the Taylor-cone shape. We confirm that the alternating expansions of the discharge and the water droplets are not allowed when the superimposed impulse dose not contain the long tail. The frequency component of the long tail is roughly equal to the natural vibration frequency of the hemispherical droplet on the needle tip. We confirm that the stability of the water spray propagation strongly depends on the frequency components of the superimposed impulse.

This paper explains a new technique based on the eddy current testing to evaluate plating thickness in the continuous galvanizing line. Previous techniques cannot apply to the line due to need low and/or fix liftoff. Because test samples are vibrated in the line by gas wipers. The new technique which we propose can evaluate the thickness with high and variable liftoff. Thus, the sensors based on the technique can install to near gas wipers which control the thickness and vibrate the samples in the line. First, the detection principle of the technique and the method of applying are explained on simulations by using the finite element method. Application results on measurement experiments are secondly explained. These results demonstrate the possibility of making thickness measurements using an eddy current with high and variable liftoff.

The developments of SiC power devices has been proceeded remarkably since 1990. SiC power devices have been payed attentions as one of the candidate power devices for next HVDC transmissions and its R&Ds have been started in the KANSAI electric power company since 1995. In this paper, a series of R&Ds for the SiC devices and SiC inverters performed in the company are presented from the historical viewpoints.

Harmful water trees, such as penetrated water trees bridging insulation, have not been found in removed dry-cured and extruded three-layer (E-E type) 6.6 kV cross-linked polyethylene (XLPE) cables since they were introduced into electric power systems more than 30 years ago. However, water-tree degradation becomes a serious problem as the operating duration increases, making it essential to diagnose water-tree degradation. Therefore, to establish the degradation index of water-tree degradation for these cables, growth of water trees should be accelerated for removed XLPE cables. In this study, an accelerated water-treeing test was performed for dry-cured and E-E type 6.6 kV XLPE cables removed after approximately 20 years of operation. As a result, we successfully found a penetrated water tree in one of the XLPE cables. Additionally, for the cable with a penetrated water tree, the values for electrical insulation characteristics, such as a DC leakage current, an AC superposition current, and dielectric loss tangent, were investigated. As a result, its DC leakage and AC superposition currents were above the threshold values indicating the existence of at least one penetrated water tree for E-T type 6.6 kV XLPE cables, whose type is older than E-E type. This result suggests that DC leakage and AC superposition currents are useful in finding penetrated water trees in water-tree degradation diagnosis for dry-cured and E-E type 6.6 kV XLPE cables.

Quantum chemistry computing is applied to estimate the Terahertz spectra of Fatty Acid Ester, which has group vibrations caused by intermolecular interactions, three-dimensional structure of substances and so on. The conformation and distribution of the molecule are very important to predict terahertz absorption spectra. Since ester oil consists of various molecular structures, then Boltzmann statics is proposed to estimate the group vibration spectra in the paper. Measured spectrum approximately coincide with the simulation results. This method will be widely applicable to estimate the terahertz absorption properties.

Whistling competitions have been held regularly in Japan in recent years, and some prize-winning whistlers have established music classrooms to teach musical whistling. However, in our survey, one-third of people could not whistle. Our work studied the principles of sound production in human whistling, using physical models of the human vocal tract. The models were obtained from an X-ray computed tomography (CT) image of the vocal tract during whistling. However, it is hard to explain to the person who cannot whistle how to whistle. To overcome this problem, we showed the shape of the mouth when the whistling sound was the loudest. To this end, we used a physical model of the human vocal tract based on its X-ray image when the five Japanese vowels were being uttered. We demonstrated that a whistling sound was generated during the utterance of all five vowels, and that the best mouth shape was obtained in uttering /e/.

This paper describes an effect of transient electromagnetic fields on the germination of seed plants. In our experiment, two kinds of transient electromagnetic fields by spark discharges were applied to seeds of radish, turnip and potherb mustard. In this experiment, the pulse widths of discharge current (800 A) were set to 3 µs and 15 µs, respectively. As a result, we found that the germination rates for the pulse width of 3 µs became greater than others (control [no application] and the pulse width of 15 µs) by around 14-20% especially when the temperature was low.