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The Ar-SF6 inductively coupled thermal plasma (ICTP) at atmospheric pressure was successfully generated for different SF6 admixture ratios in order to investigate the quenching effect of SF6 injection on thermal plasma from the viewpoint of elucidating a remarkable interruption ability of SF6. Spectroscopic observation was carried out to measure the radial distributions of the radiation intensity of Ar lines and temperature for the Ar-SF6 ICTP. It was found that only 0.5% SF6 injection caused a 1/2 decrease in the radiation intensity and 1000 K decline in the temperature on the centre axis at 10 mm below the coil end. A two-dimensinal hydrodynamic model was developed for Ar-SF6 ICTP to simulate flow and temperature fields on the assumption of the local thermal equilibrium. The results obtained from the calculation indicated that a little SF6 addition to Ar ICTP decreased high temperature area above 9000 K drastically. This temperature decaying tendency agreed with the experimental results.

This paper deals with a novel method of calculating radiation dose rate within a building and around its surroundings. We employed the Monte Carlo method to calculate the direct gamma rays absorbed in an object. The buildup fluxes caused by the Compton scattering were simply treated with the buildup factor as a function of the mean free path of photons. The proposed method was benchmarked for a simplified geometry case and compared with the point-kernel integration code QAD-CGGP-A. The results of both methods were in good agreement. The proposed method could be used for predicting radiation dose rate in the fission products deposited areas.

This paper presents new developed noise reduction methods and results of partial discharge detection and measurements of electric power apparatus using digital signal processing techniques. We have examined noise diminution by the algorithm in laboratory based on measurements of PD signals in SF6 gas and real noise as well as interference in practical HV and EHV substations. Consequently, the techniques, enabled us to reduce sinusoidal continuous noise considerably, so that they are promising for future application in actual HV substations.

application/pdf Improvement of the generation power in micro-hydraulic turbines is shown in the range of low flow rate and low head using a new inverter generation system. The generation power can be obtained down to very low flow rate and head using the new inverter generation system with variable rotational speed control, where a water turbine connot produce the electric power in a normal constant-speed-control system. Experiments were carried out using a practical micro-hydraulic turbine with 2 kW output and variable rotational speed in a forest on the mountain, Mie University. The total efficiency is kept at a high value even in the very low partial load area. Compared with the constant speed control, the generation power is improved over 20 percent by varying the rotational speed.

Establishment of an early trouble diagnosis system is demanded to prevent damage of wind turbine generator. Therefore, AE signal occurring by the damage of a wind blade was detected with the AE sensor which installed to the body of wind turbine generator and a pole. In this study, length of a blade of a small wind turbine generator was changed as simulated trouble in the constant wind velocity. The AE signal which occurred at this time was measured with an AE sensor. The signal was processed by FFT analysis, and a change of spectrum strength was examined. Then, trouble diagnosis technology of 50W grade small wind turbine generator was developed. As the results, a method to count the number of times more than threshold of AE signals was suggested by a wave pattern of an AE signal. It was understood that the number of the count was decided as standard to judge normality or abnormality of 50W grade small wind turbine generator.