An active vibration control system has been developed for JR maglev vehicles. The system consists of six hydraulic actuators, four for vertical and two for lateral control forces, six accelerometers as co-located sensors and an electric controller. The actuators are inserted between the bodies and bogies of articulated cars. Random shake tests were conducted with a half-scale model of one bogie-two body system. Comparison between active control with actuators operating and passive vibration isolation with oil dampers showed the superior effect of the active system. Through evaluation of the calculations and tests, it is expected that the active system will give a better ride quality for maglev vehicles than existing Shinkansen bullet trains.

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The chains for the 2nd order moment compensator in the marine diesel engines are designed usually to have extremly large safty margin. However, in a certain ship with the relatively large counter weight to reduce the hull vibration, it is possible to occur the non-linear vibration of the chain by the two node torsional vibration of the crank shaft.
For this problem, the non-linear vibration analysis of the chain was carried out with the measured spring characteristics by means of the chain tightener mechanism, which was represented by the form of T_q=k₁⋅θ+k₃⋅θ³.
In order to avoid such a non-linear vibration of the chain, it is important to increase the socalled ith order critical speed n_c= (60/2π) √k₁/I/i of the chain, which is related to the linear part of the chain spring characteristic k₁, comparing with the rated engine speed n_MCR. This can be obtained by increasing k₁ or decreasing the moment of inertia I of the counter weight. Also, the increase of k₁ is able to be realized by increase of the initial chain tension F₀ or by stepping up the size of the chain and etc.
From this point of view, in this paper, a security evaluation method for the chain was considered in relation to the value of n_c/n_MCR, on the basis of the reaults of the non-linear vibration analysis of the chain.

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In this report the longitudinal, torsional and two directions of lateral vibrations on the shaftings of large, low-speed, seven-cylinders, in-line marine diesel engines and a small, high-speed, ten-cylinders, V-type automobile diesel engine are calculated first by the 3 dimensional analysis of forced vibration using the transfer matrix method, which has been developed by the authors.
Next, the calculated results are compared with the corresponding experimental results for investigating the characteristics of the 3 dimensional vibrations and also the adequacy of the analytical method.
As a result of the comparisons of the calculated results with the measured results, the following conclusions are obtained;
[1] The calculated results are approximately similar to the measured ones. From this comparison, it can be assured that the use of this 3 dimensional calculation methods enables the estimation of the longitudinal, torsional and two directions of lateral vibrations, including the coupled vibrations, provided that the correct input data are specified.
[2] The characteristics of the forced vibrations of the large, low-speed, marine diesel engines and the small, high-speed, automobile diesel engine are partially made clear.

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Recently, vibration damping steel sheet (VDSSs) are broadly applied to many types of industrial products for reducing noise and vibration. To valuate the effect of VDSSs on noise reduction of ship's structure, two types of experimental studise, i.e., onboard one and laboratory one, were carried out. By the result, it is concluded that the application of VDSSs for ship's structure can be a effective measure for noise reduction.
Onboard experiment was carried out on the training ship “Gingamaru”. In the experiment, VDSSs were partly fitted on cabin walls which were made of steel plate by welding. The nice level measured during sea going condition and berthing condition. Reduction of noise level due to VDSSs were 6 dB (A) and 14 dB (A) under sea going condition and berth ingcondition, respectively.
In the laboratory experiment, open top box type model were used. One model was made of VDSSs and the other was made of ordinary steel Plateas the reference. The distributions of vibration of both models were measured and compared. By the result, it is pointed out that the VDSSs is effective for reducing vibration having the frequency higher than 500 Hz.

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Measurements of physiological and psychological changes of subjects have been carried out under whole-body exposure to low frequency oscillations by using ship-motion simulator. Electroencephalogram, Electrocardiogram, facial expression, face surface temperature, are measured as the physiological effects, and symptoms of motion sickness or ride-quality are measured as the psychological effects. Methods for analyzing the measured results have been also developed. In this short monogram, results as well as methods of measurements, analyses are described.

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