Carbon dioxide (CO₂) is considered as one of the sulfur hexa-fluoride (SF₆) alternatives for arc-quenching gas. In this paper, polytetrafluoroethylen (PTFE) was assumed as the nozzle material of the gas circuit breaker. The dielectric properties in the hot CO₂ gas contaminated by PTFE vapor were calculated in the temperature range of 300K to 4,000K at a pressure of 0.8MPa. In this calculation, not only 48 gaseous phase species but also the carbon in solid phase one (graphite) were adopted as component species. It is derived that at temperatures below 2,000K, the critical reduced electric field strength of the hot CO₂ gas contaminated with PTFE vapor becomes higher than that of pure CO₂ as the PTFE vapor concentration increases. By contrast, in the high temperature region exceeding 2,000K, the critical reduced electric field strength is less than that of pure CO₂ when PTFE contamination is 20% or 40%. The dominant reactions governing the critical reduced electric field strength are discussed and listed in the Tables. It is concluded that the dominant reactions are brought about by the dominant particles or particles having large electron collision cross sections.

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In this paper, I focused on a town, Shimokitazawa. By examining the activities of musicians there, I considered the relationship between the urban user and the place. A pop musician's occupation is singing her/his songs repeatedly. As the facilities where they play their music are scattered around the city, they move around as mobile laborers in a similar manner like nomads. Therefore, the audiences who appreciate the performance of the musicians are called mobile consumers. To understand some of these actual situations, I investigated the facilities that hold such music performances in Shimokitazawa and the behaviors of three musicians who give these performances around the town and an audience. I considered the relationship between the musicians and Shimokitazawa by focusing on the former's practices in their music performances, especially in 2005 and the musical landscape depicted in their songs. The upsurge of the redevelopment problem was observed in Shimokitazawa around 2005. As a result, it can be said that music played the significant role in the development of people's connections with the musicians, and of positive associations of the musicians with the town.

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