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One of the elements of tire stiffness is sidewall stiffness. This stiffness, which influences tire vibration characteristics, is also an important design parameter for carrying the vehicle body. Tire is one of pressure vessels and inflation pressure is dominant in sidewall stiffness. Thus, tire sidewall stiffness is decided from the tension of inflation pressure and the structural dynamic, including the properties of the rubber material. To reveal the dynamic characteristics of tire sidewall stiffness, this study describes differences in stiffness due to inflation pressure. It can be expected that variation of inflation pressure is monitored from the axle vibration response during vehicle traveling in the future. That is because the relationship of the vibration characteristics and the inflation pressure of tire are derived by sidewall stiffness. First, we derive a formula for sidewall stiffness based on the structural dynamics of Akasaka's theory.

Sulfur storage/discharge behavior on a flow-through type oxidation catalyst (FTC) was investigated by engine dynamometer tests and laboratory tests, and the following results were obtained. In FTC wherein active Al2O3 was used as a substrate for supporting catalytic components, sulfur was stored in the form of aluminum sulfate in high temperature region while sulfate were adsorbed or adhered to the catalyst surface layer to be stored thereon in low temperature region. Although aluminum sulfate formed in high temperature region was relatively stable, sulfate stored in low temperature region were desorbed easily when the temperature rose. Therefore, it was attempted to optimize the substrate deposited catalytic components. And, FTC which would inhibit adsorption of sulfate was achieved successfully.

The reduction behavior of diesel particulate and SOF by flow-through type oxidation catalysts was investigated under steady and dynamic engine conditions using a current fuel (S content:0.38 wt%) and a low sulfur fuel (S content:0.04 wt%). Each catalyst gave 40 - 90% SOF reduction at exhaust gas temperatures between 100°C to 500°C. This SOF reduction behavior is explained as follows. SOF is adsorbed or adhered on the catalyst surface at the lower temperatures and is decomposed at the higher temperatures. Pt only load catalyst which has high SO2 oxidation ability resulted in a low total particulate reduction due to high sulfate formation at higher temperatures even when the low sulfur fuel was used. It has been shown that flow-through type oxidation catalyst with low SO2 oxidation ability will offer a practical exhaust gas treatment method for 1990's improved diesel engines. 50 - 60% SOF reduction and 40 - 50% total particulate reduction has been proved to be possible.