Since the first industrial revolution in the eighteenth century, technological progress has increased the size of human society and made people richer. Large, rich societies have made technology progress more and more.
Since the second industrial revolution in the middle of the twentieth century, which was brought about by the invention of microelectronics, computers and the advent of mechatronics, the interaction between technologies and societies has accelerated. As a result, technology and society have become a completely unified unit in a technology based modern society. These societies are also very large, complicated, and systemized.
Large technologies consume vast amounts of energy and resources.
Complicated, systemized and off iciencyoriented societies suppress individuals.
In the early 1970' s, energy first arised as a world-wide issue, and then, in the 1980' s environmental issues come to light.
In the 1980' s, the spiritual aspect of human beings began to attract more attention. Also in the 1980' s, safeness of large and complicated technology arised as a world-wide issue due to the accidents at Three Mile Island and Chermobyl.
In this world of large and complicated technology, studies on the above mentioned issues are required not only from specif f is points of view but also from the macroscopic point of view. Therefore, the authors have been conducting studies on specific technologies of safety and environment along with a study from the viewpoint of system science.
In this paper, we discuss the saf eness of atomic energy plants as well as of automobiles. The authorities of the atomic energy plants maintain that atomic energy plants in Japan are completely safe. They also argue, the plants are safer than automobiles because many people are killed and wounded in traffic accidents while casualties are very few in their plants. We show that their arguments are unreasonable from the viewpoint of system science.

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Digital governors have advantages of digital signal processing and dynamics mapping. Torsional vibrations of low speed engines can be reduced significantly.
All electric actuators will be used more but the work capacity is somehow different from hydraulic powered actuators.

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A new particulate trap system is developed. A failure caused by combustion heat has been one of the serious problems in the existing particulate trap. The new trap eliminates this problem by removing the trapped particulate from a filter elment with reverse air flushing. Removed particulate gathers in the bottom of the trap where the electric heater burns the particulate gently.
1000 hours durability test was carried out. No serious problems have occurred during the test, which certifies that the trap has enough durability. Exhaust smoke reduced from 2.5 to 0.1 in Bosch Smoke Number by the trap.
Particulate reduction was also tested using dilution tunnel. Dry soot reduces to the negligible order. SOP, on the other hand, remains when the engine load is hige. SOF, further more, has hysteresis against the engine load.

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High reliability of main engine remote control system is required, because system trouble affects people's lives. A micro computer is often used for system in recent year. So reliability of both hardware and software are requird.
We used“NAS LANGUAGE”for the programig of the software. This language is a new developed high grade compiler for micro computer which is designed by NIPPON AIR BRAKE CO., LTD. This language is designed for the program of micro computer based control systems. By using this language, conventional electric or mechnical engineers make the program easily instead of expert computer programers. So, it just fit for main engine remote control system, which is needed to manufacture for a short time and to be adapted to the various customer's request.
The programing is easy even for electric or mechanical engineers who have no special skill for computer programing, because the data input can be made by the conventional relay sequence diagram or logic sequence diagram. This language is not only very useful for understanding and confirming the specification of customer's engineers but also very easy to modify or to check the specification of the program.

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The evaluation indices of the reliability and safety are extremely important for user and producer of ship industry.
The reliability indices can give a range of some concrete desired values that satisfies with economic dfficiency and continuous running ability. Especially the safety index provides an economical running guidance.
If the above evaluation indices can set up, some important guidelines can give to both the users and producers.
On the other hand, a reliable improvement goes on a marine diesel engine and a mechatronics, and safety also is tending upward.
However, it is difficult to say that reliable improvements of total systems are going up.
According to a great number of the field data that collected from Mo Diesel Ship (131 rears-vessel), the reliability and safety in a ship evaluation during 1983-88 changed as follows.
1. The total manning index MI, which means a maintainability, of 1000 hours, and also failure rate per 1000 hrs times man hour per case, decreased to about 60% within 6 years with respect to a total engine system.
2. MI in a general failure and heavy ones decreased from 73 to 43 and from 19 to 11 individually for the total system.
3. MI in both failures of two subsystems of of main engine and auxiliary machine failures occupied a half of all and each MI decreased to 66% in 6 years.
The availability that is picked up as the index of safety, has been decreasing as the average number of operator decreases since the second surveyed period in 1984-85.
The unavailability is deteriorating with 0.13-0.18% conversely, although 0.09% are indicated in 1985.

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Recent years, Cogeneration system has been rapidly extending as a one of means of effective exploitation of energy in the industrial market.
Since wide range of customers perceived the advantage and merit of the products, it slso spreaded to the commercial market such as hotels, and hospitals, etc.
As a result, many unskilful people are bound to operate the machine.
On this point, the monitoring system for the machine has come to be necessary taking also into an account extremely hard use of the products.
This kind of monitoring system is also increasingly applied to the marine engiines due to decreasing number of the expert engineers.
The remote monitoring in the center has been demanded to be established so as to fulfill the efficient maintenance service because, manufacturers need it as a countermeasure to solve the problem of difficult prompt service to the broadly scattering customers of the cogeneration system in the market.
Concept of the monitoring system to use the personal computer that is almost parity to the mini computer of last couple years, which is achived by the recent remarkable technological development of micro processor, will deserve the credet for its finer function and less expences.

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In recent yesrs, diesel engine has become like a black box for the user due to introduction of mechatronic systems and/or automatic systems. Consequently, it will be difficult to correct troubles or to improve abnormal condition of diesel engine.
To overcome the above-mentioned problem, diagnosic systems of diesel engine based on the computer have been developed. However, these system normally require special sensors for the purpose of diagnosis. Thus, initial cost, reliability and maintenance of the sensors are becoming problems.
We have developed an expert diagnostic system of engine performance, without adding any special sensor. The system diagnoses diesel engine troubles by using both expert knowledge gathered from experienced and skilled engineers, and information obtained from ordinary sensors such, as pressure gages and thermometers. This pater describes new system which diagnoses air and gas flow performance of diesel engine with a turbo charger.

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