There are many subjects that relate to electrical and electronics circuits. Recently, practical education for those subjects usually introduce hardware description languages such as VHDL and Verilog HDL, but it is not easy to understand the relation to the basic logic circuits drawn as circuit diagrams. In this paper, we introduce practical education in which basic digital circuits are drawn, simulated, and executed on an experiment board with a programmable logic device, and then newly designed 2-bit CPU which uses those basic digital circuits are drawn, simulated, and executed on the experiment board. Students can learn basic digital circuits themselves, and their operations which relate to each other in the newly designed 2-bit CPU. By the tests and the questionnaire survey, the effectiveness of the newly introduced practical education is confirmed.

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The electric double layer capacitor (EDLC) electrode is made of carbonized and activated materials. The material surface and electrical characteristics of carbon materials produced from low cost organic materials were examined. First, a cotton cloth was carbonized and activated, and its optimal time and temperature of carbonization and activation processing were examined. And, its surface area, pore volume and pore size distributions were analyzed. Second, activated carbons were applied to the electrodes of 1Wh class EDLC cell with water electrolyte solution. The capacitances and internal resistances of the assembled EDLC cell were measured by a charge and discharge circuit using constant voltage source. And, the charge and discharge cycle test was performed on these assembled EDLC cells under practical use condition. As a result, EDLC cells using the activated carbon with large surface area of 1300m²/g showed the high density of capacitance 0.5-1.1F/cm². The internal resistances of EDLC cells were less than 0.34W. It was also found that the EDLC cells had no deterioration in the charge and discharge cycle test under practical condition. It shows that the activated carbon made of cotton cloth contributes to the low cost and safety electrode of an EDLC.

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We have succeeded in developing new dynamic-micro-plasma-excited deep ultraviolet light emitting device using Aluminum Gallium Nitride (AlGaN) multi-quantum wells (MIPE), of which operating principle is completely different from current-injection type deep ultraviolet light emitting diode. We have realized a 12cm×5.5cm size device with a power of about 1W at the wavelength of 325nm. We can realize panel type laminar flow water purification and air cleaning systems which can be alternative system using DUV light source of mercury lamp, of which no usage is required by Minamata treaty. The wavelength region from 210nm to 250nm realized in this device opens new academic and application fields in which decomposition of hard materials and synthesis of new materials including a new H₂ battery cell as well as disinfection of water are expected.

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One- and zero-dimensional numerical models of plasma generated over a solution were established. Gas- and liquid-phase reactions and mass transfer through a gas-liquid interface for OH radical, hydrogen peroxide, and HO₂ radical were considered, and the decomposition of acetic acid in water was evaluated. In one-dimensional model with a small diffusion coefficient (10^-9m²/s) in liquid phase, the diffusion rate was the rate-limiting factor of the decomposition of acetic acid. With such a small diffusion coefficient, the concentrations of OH radical and acetic acid in the zero-dimensional model showed large differences from those in one-dimensional model. When the time scale of diffusion in liquid phase was shorter than that of decomposition reaction between OH radical and acetic acid, reasonable results were obtained in the zero-dimensional model.

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Advanced oxidation process (AOP) with hydroxyl radicals (OH) is considered to be useful for water purification through oxidation; therefore, we proposed an underwater plasma source with a porous glass membrane which functioned in bubble supply and the formation of micro-discharges. We observed bubble formation and light emission from discharge on the surface of the membrane using a high-speed camera and a spectroscope, respectively. Additionally, dependence of gas pressure on generation of OH radical and decomposition of recalcitrant organic matter were examined. The obtained results showed that AOP might be more effective when the operating gas pressure was set higher than a pressure which could form bubbles.

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In general, a polymer insulator applied high voltage reaches a breakdown through a development of electrical trees. Magnesium hydroxide, metal hydroxide, has the property of releasing crystallization water at a high temperature. If the energy of the partial discharge is used by the decomposition of the magnesium hydroxide, the growth of an electrical tree will be constrained and the lifetime of the polymer insulator could be expected to improve. Therefore we have studied the effects of the magnesium hydroxide on treeing. It was confirmed that the electrical breakdown lifetime of epoxy resin with 30 phr of magnesium hydroxide was 100 times longer than that of the epoxy resin without it. Magnesia was detected by the electron beam diffraction analysis of the fillers located near electrical tree, and it showed that a dehydration reaction of magnesium hydroxide was took place. In other words, as an explanation of the restraint effect of an electrical tree, the effect of the energy dispersion of partial discharge was suggested in addition to the barrier effect of the fillers.

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In order to study the acoustic noise generated by transformer cores, the impacts of types of core joint and the number of laminations per layer on noise levels were investigated. In addition, localized magnetostrictions on transformer cores were measured with strain gages, and the differences caused by types of core joint were investigated. The followings were obtained as the results. The step-lap configuration reduced noise levels in comparison with conventional lap. The increase of the number of laminations per layer raised the noise levels. The differences occurred on the higher harmonic components than the fundamental component. There was a certain connection between localized magnetostriction and noise with respect to types of core joint. The magnetostriction measured on a single sheet sample with sinusoidal excitation had less correlation with the localized magnetostriction measured on the core.

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In order to increase the sensitivity for detecting defects and reduce the voltage gain displacement by the lift-off variation, we demonstrated the improvement of voltage gain from the exciting coil to the detector coil using resonant circuits based on the equivalent circuit analysis. We used three (exciting coil, detector coil and metallic specimen) equivalent circuits that are coupled with each other through mutual induction. The two relationships (exciting coil and specimen, detector coil and specimen) were analyzed using a multi-layer model that consists of the coil, the air and the metal. The mutual inductance between the exciting and detector coils was taken from the result of preliminary experiment without resonance. According to the analysis, the voltage gain increased by up to 6.8 times and the voltage gain displacement reduced using resonance. In the experimental demonstration under the same conditions as the analysis, the increase of voltage gain was consistent with the analysis result within a prediction error of 4 % on average. From this demonstration, we confirmed that the resonant circuits were effective to increase the voltage gain and reduce the voltage gain displacement for improving the characteristics of eddy current testing.

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We have improved previously developed compact magnetometer using HTS-SQUID with rotating sample. In the previous system, the attenuation of rotating speed had resulted to the deformation of the averaged waveform signal, reducing the reproducibility in measurements. In this paper, we have used a more superior motor in order to decrease the attenuation of the rotational speed for the precise averaging of the output signal and improving the signal-to-noise ratio. Moreover, to improve sensitivity, we optimized the pickup coil and compared the signal-to-noise ratio of the circular and elliptical pickup coils which having the same number of turns, resistance and inductance. As a result, the signal-to-noise ratio was improved with high accuracy and the magnetometer showed susceptibility sensitivity of 3.8×10^-9 emu.

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Doppler spectroscopy diagnostics with a new reconstruction method has been developed to evaluate local ion velocity profile of magnetic reconnection outflow. The multi-chord ion Doppler diagnostic can simultaneously measure spectral profiles of line-integrated emission from 90 chords across the plasma using three monochromators and three intensified CCD cameras. Under an assumption of axisymmetry, 2-dimensional profiles of reconnection outflow ion velocity are achieved with satisfactory accuracy by a vector-based tomography technic for the first time.

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The principle of sound production in human whistling is not well-known. The purpose of this letter is consideration on the principle of sound production in human whistling using physical models of the human vocal tract based on the X-ray CT data. This letter shows that the pitch shift and overblowing phenomena in human whistling are explained by the vocal tract model.

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We know that the optimum color temperature for Japanese style garden in autumn is 2000K. But at that time, we supposed that the red color of plants maybe affect the results, so we did the experiment in other three seasons in this time. As a result, 2000K is also highly evaluated in other seasons, and the color of plants in garden which changes by season affects the Evaluation factor more than the Activity factor.

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Silicone gel is widely used to encapsulate power electronic circuits. It is known that the weakness of this insulation system is the triple point which is composed of metallization, gel and substrate. Partial discharges (PDs) occurs at this triple point and propagates between gel and the substrate. The propagation of PDs gives rise to electrical degradation, which may lead to eventual failure of the insulation. Despite the fact, surface discharges in gel has not yet been studied enough. Therefore we have obtained images synchronized with the applied voltage. It showed that the degradation occurs when the applied voltage is positive.

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The activated carbon sheets made of cotton cloth were applied to the EDLC electrodes. The capacitance and internal resistance of the assembled EDLC cell in a beaker were measured. The density of capacitance was approximately 1F/cm² in the EDLC electrode. The internal resistance was less than 1Ω in the EDLC cell. It was confirmed that the capacitance of active carbon sheet made of cotton cloth is in proportion to the area of active carbon sheet. From the obtained results, there is a possibility of the practical use of EDLC which is made of the carbonized and activated cotton cloth in low cost.

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[in Japanese]

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