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This paper deals with the development of plastics recycling technology, which is one key to resolving environmental and natural resource problems and encouraging recycling activities. Bumpers are among the heaviest plastic auto parts, so the technology for recycling bumpers is strongly required. Paint remaining on bumpers causes the strength of the recycled material to decline and degrades its surface quality. Therefore, unless the paint is removed, it is impossible to use recycled material to manufacture new bumpers. This hampers recycling efforts and results in low-value recycled material. Consequently, it is essential to develop a simple paint removing without chemical substances for practical plastics recycling at low cost. Two topics are discussed in this paper. The first concerns the mechanism of paint removal and the development of a technique for utilizing that mechanism.

A large-size truck is equipped with a variety of audible warning devices. These warning devices are grouped into three categories by their usage, i.e., malfunction type, proximity type and attention type. The sound characteristics of warning sound that are investigated for each type are signal envelope, fundamental frequency and the number of harmonics. Many sounds are synthesized with nine fundamental frequencies, ten or fewer harmonics and two signal envelopes. With volume fixed, these sounds are evaluated using an unpleasantness rating scale, and the functional impression of these sound is also chosen. From the results, the range of fundamental frequencies, the number of harmonics and the shapes of signal envelopes for preferable sound quality are determined.

Owing to many excellent previous studies brake noises have been improved steadly, yet it is not easy to get effective remedies for improving the noises of dram brake. The authores took experimental analysis to find the cause of the noise of 650-670Hz on medium class trucks and buses. They found out that the main sourse of the noise is the backplate vibration caused by vibration coupling of 2 vibration systems, namely drum-shoe system and backplate system. This coupling was faded and dissolved by separating the resonance frequency of either system from another. This method was effective to prevent the brake noise. They conclude that the brake noise is caused mainly by vibration coupling.