[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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This paper proposes to represent the configuration of protective devices for safety assurance by using as operators as possible and to clarify the safety configuration and characteristics of the protective device by using the logical representation. The configuration of a system is represented by the monotonous logical structure of signal transmission, and the signal transmission process of the system is represented by 13 operators. Application cases are presented to indicate that the safety configuration and characteristics of a protective device can be logically elucidated by use of the operators. When the protective device is constructed by containing negation, it has assumptions or limitations established for its safety assurance performance. Examples are given to describe such assumptions or limitations and how to cope with them.

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This paper proposes a decentralized autonomous interlock system. The decentralized autonomous interlock system consists of a safety-related part and a non-safety-related part. The safety-related part implements its required functions by assigning one unit to one track circuit and wiring the units according to the topology of the track. The units are available in two types : One type is the no branch path unit that is assigned to a track circuit without branch path. The other is the branch path unit that is assigned to a track circuit with a branch path. Each unit is implemented by dynamic fail-safe signal processing.

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This paper discusses about the applicable techniques of general-purpose LAN for the safety-related transmission in the ATC (Automatic Train Control) system and that evaluation. The authors adopted Ethernet as a general-purpose LAN. Subjects in application to the safety-related transmission of this were put in order from the requirement of the safety-related transmission in railway signalling applications, and three extreme important subjects are securing of periodic transmission, the transmission of the latest data and defense from the illegal data. These subjects could be solved by the adoption of switching HUB, the plan for new method of sequence number check, the establishment method of the securing safety when the non-safety-related general equipment connects it and so on. As that result, ATC system which used general-purpose LAN, and practical use could be started.

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The importance of immediate remedies for quality, reliability, and safety problems cannot be overstressed. Prevention of their recurrence is also very important. If their effects on a society or an entire organization are extremely vast, recurrence prevention is insufficient, and the key is preventing them in advance. In quality crises, human factors play important roles. For preventive measures, advance disclosure of potential human errors is very important. This paper presents two methods that reveal human errors : guide words analysis of human errors and similarity analysis of product use focused on the function of a product. The former focuses on deviations from the correct use, and the latter focuses on uses that manufacturers had not intended for their products. More than 95 percent of the errors that cause consumer product accidents were revealed in a list from a reporting information system by applying the proposed methods to find error modes for three kinds of consumer products.

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