Disasters have complicated causes and effects. Various parameters on disasters such as the ratio of the wounded to the dead (referred to as the W-to-D ratio), the mean time between accident (referred to as MTBA), the parametermof Weibull distribution give insight into the characteristics of various disasters.
Recent statistics on marine disasters near by Japan are analyzed to find such parameters mentioned above. The result is compared with the similar analysis on other disasters on the street, railroad, air traffic, and also with similar analysis on fire hazards, typhoon damages and earthquakes. The MTBA of marine disasters are around 20 years per one accident and 200 years per one death. Both numbers are of the same order-of-magnitude as other means of traffic. However, the W-to-D ratio is nearly unity and next to the worst, which is the air accident. The Weibull parametermis of the same order-of-magnitude as other means of traffic, which is worse than fire hazards but better than earthquakes.

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The shaft generator with thyristor inverter which is driven by main engine of a ship with fixed pitch propeller is highlighted as an energy saving and less maintainance generator.
We recently developed a large capacity shaft generator with thyristor inverter first in Japan, and installed on four (4) 130, 000 DWT bulk carriers we built.
This report describes an outline of the shaft generator and problems associated with its design and construction.

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In the former paper, based on the Weibull model, we investigated the relationship between the optimal replacement interval, its corresponding replacement cost per unit time and the cost ratio of replacement through the variation of the shape parameter.
The object of this note is to provide the procedure for calculating the minimum cost per unit time and the optimal interval of each replacement policy by using the results already obtained in the former paper.
The numerical examples are illustrated by utilizing the field data in order to show the usefulness of the calculation method given in this note.

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Consideration on hierarchical structure of energy system is very important for energy saving. But there are many problems remaining unsolved and available energy is not used generally yet. In this paper, considering a mathematical model of energy flow, a mechanism of available energy loss is analyzed on hierarchical structure. And an energy system in different condition for outer system of element is evaluated by available energy.

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In the previous study combustion characteristics were mainly investigated based on engine tests and, as a result, FCC oils were found to be the most problematical not only in wear but also in combustion.
In this study it was tried to establish some methods to identify FCC oils. The main results obtained are (1) the molecular weight charts of GPC can clearly identify FCC oils (2) evaporation diagrams of TGA are, however, unable to identify them and (3) “particle gauge” is recommendable as an instrument on board because the gauge enables it not only to detect FCC catalyst fines but also to make broad estimation of their content in a simple practice.

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Inert Gas System (IGS) which was developed to prevent the explosion of tanker, discharge acid water of large quantity to sea in harbour. MARPOL of 1973 for sea pollution regulated to equip IGS with COW, therefore the number of IGS tanker increases and the pollution by effluent water of IGS is concerned.
With regard to the prevention of pollution by IGS previously, the surveys of water discharge from IGS and surveys of surrounding sea water were made in 4 harbours, and the studies of mechanism of the scrubbers were carried out by a pilot test plant of IGS. The results of the surveys and the studies were showing as follows:
1) Pollution caused by the water discharge from IGS was not recognized. Although the value of PH in the effluent water were 2-3 and the value of the total sulphur increased, the water discharge from IGS were completely diluted and varied chemically.
2) By multistep scrubbers used in the tests, a few kinds of discharge water were gained. The effluent from the former step scrubber were acid water and contained many sulphur. The water of the after step scrubber were rather clean.
3) The extraction efficiency of SO₂gas varied by the steps of scrubber and by the quantity of water.
4) For the purpose that the extraction efficiency of SO₂gas was performed 100 per cent, it was necessary to supply the water which quantity was 0.6% of the volume of the gas for the scrubber at least. But for the high content SO₂gas, the studies must be continued still more.
5) The studies are carrying out using sea water for the scrubber.

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