The authors have newly developed an Electrostatic Cyclone DPF to reduce PM emission in diesel exhaust. The PM collection test with the DPF was investigated using two types of marine diesel engines, i.e., a low speed two-stroke engine (3UEC37LA, 1105 kW, 188 rpm) and a high speed four-stroke engine （3L13AHS, 74 kW, 1200 rpm）. Two types of fuels, MDO with a sulfur content of 0.07 % and HFO with a sulfur content of 2.2 %, were used for the tests.
 The results of the tests are as follows: (1) The Electrostatic Cyclone DPF can reduce PM emission by over 90 %. The DPF has high collection efficiency not only for soot but also for sulfate and soluble organic fraction (SOF) in PM. (2) The PM collection efficiency for HFO was higher than that for MDO; therefore it was confirmed that the DPF is applicable to marine diesel engines operated with HFO. (3) The majority of the PM particles have diameters less than 500nm, and the PM collection efficiency for particles smaller than 100nm is greater than 95 %. (4) An exhaust gas processing system which can reduce PM, SOx and NOx is realized by application of the DPF. The proposed exhaust gas processing system consists of the DPF, the scrubber and the EGR system.

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 Wear characteristics of stainless steels were investigated using an orthogonal two cylinder type experimental machine. Cold drawn bars of austenitic, ferritic and martensitic stainless steels were used as the specimens. Structure of the specimens was observed and the hardness distribution was measured. Investigation of the progression of wear revealed the existence of three modes of wear for all types of stainless steels. Mode 1 which causes the first wear is the category of mild wear. Mode 2 which causes the second wear is the category of severe wear. Mode 3 which causes the third wear is the combination of severe and mild wear.

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 It is essential to comprehensively analyze human errors occurring during marine engine plant operation, and to investigate more effective measures in order to prevent the occurrence of similar errors. In this paper, a classification model of human errors related to marine engine accidents is proposed. The judgment records of Marine Accidents Inquiry Association were examined for cases that involved human errors. In the present work, 298 marine accidents during engine operation between 1995 and 2011 were investigated to clarify the potential factors using the quantification theory III. It is expected that safety measures can be strengthened through proper understanding of the numerous factors that contributed to these errors.

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 Boats with low vibration and noise offer one of solutions to ease the fish avoidance behavior. The vibration and the noise generated by the water-jet electric boats are low compared with those of same sized internal combustion engine boats. However, an objective evaluation of the vibration and the noise of electric boats has not yet been conducted. In this research, an underwater noise of an electric boat and that of an internal combustion engine boat, which is particularly under the audible sound frequency range of fishes, was measured and analyzed. From results of experiments and frequency analysis, maximum noise level of the electric boat was found to be lower than that of internal combustion engine boat. It was also shown that the impeller revolution was the main source of underwater noise for the electric boat.

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