The vibration isolation effect of rockwool type floating floor set up in a training ship was measured for ten years to know the vibration durability of rockwool.
The floating floor could maintain the vibration isolation ability not less than the value at the construction time after ten years.
The life time of rockwool used in a floating floor in a ship might be estimated more than 100 years, considering the on board experiments and a fatigue acceleration test of rockwool by a vibration testing machine.

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Timing belts are usually used as standard apparatus for power transmission and the timing device in the diesel engines of ships, the OHC engines of cars and the machine tools. In such cases, it is well known that the timing belt is subjected to the fluctuation of tension which is caused by the eccentricity of the pulley shaft, engagement of the belt and the pulley, and the fluctuation of torque given to the pulley shaft. As a basic research on this problem, this paper describes the results of analytical and experimental investigations of the parametric resonance phenomena of the timing belt stretched vertically. As the first step, the author regarded the timing belt as a system with string and applied Mathieu's equation to the behavior of the timing belt which is subjected to periodic tension, and then compared the experimental results with approximate stability chart for Mathieu's equation. As a result, the experimental results agreed almost with approximate stability chart for Mathieu's equation. Namely, the vibration characteristics of timing belt showed remarkable features of the parametric excitations.

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Although most of welding works have been automated recently in a sophisticated manner especially for large structures, a manual welding is still conducted for welded joints with complex configuration and for welding works consisting of various welding conditions. Formerly, skilled workers, who had undergone a special training course for a long period, have been engaged in such manual welding works. It is considered, however, that welding works of less important structures with regard strength, though being with complex configuration, could be done by semiskilled workers.
The primary concern in this paper is to develop an expert system for training semiskilled workers in arc welding in a short period. In the first place, attempts are made to acquire the knowledge of skilled worker through arc welding experiments using video systems, and the knowledges so obtained are evaluated numerically. The objective knowledges here are welding speed and crater treatment procedures, which skilled workers seem to have in their minds unconsciously. The validity of the welding works conducted by an expert is substantiated by 3-dimensional finite difference analysis concerning crater treatment form a viewpoint of cooling cycle.

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Methanol-fueled diesel engines have some technical problems. Lubrication trouble is one of them.
Authors investigated effects of alcohol injection on lubrication condition between the piston rings and the cylinder liner on a large size test rig in order to clear problems before tests on a large size single cylinder test engine (bore : 250mm, stroke : 250mm), such as the adaptability of lubricating oil.
As a result of this test which simulates the mechanism of a piston ring and a cylinder liner on a engine, alcohol injection on the sliding surface causes the improvement of lubricating performance.
On the methanol engine, a result is shown that appropriate lubricating oil should be used in order to prevent the lubrication trouble. And (1) contamination and dilution of lubricating oil are not found, (2) abnomal wear of the piston rings and cylinder liner are not found, (3) the combustion chamber parts are clean and adhesion of carbon on them is less than oil burning engines, and (4) lower base number lubricating oil should be used on the methanol engine than oil burning engines.

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