It is we11 known that, when a ship is under way in heavy seas , large amplitude of the ship motions occurs consecutively a few times as we 夏 l as large wave groups . In this paper , the number of consecutive Iarge roll and pitch amplitude was discussed , by using the motion records of the previous report . The following results were obtained . ( 1 ) The distribution of the number of consecutive large alnplitude can be calculate by the random theory. However , the observed values of the mean

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... th and standard deviation of runs were slightly larger than the calculateCt values . ( 2 ) Observed probability of the occurrence of length of runs was clarified . 1. は じ め に