Most verification algorithms for schedulability of real-time systems are based on an approximate computation which only considers worst cases. Although they always find correct schedulings, in which any task never violates its deadline, those schedulings are sometimes too strict. In this paper, in order to verify schedulability more precisely we propose a verification method based on the state space traversal of the time Petri net that models the given real-time system and the given scheduling. W e also extend time Petri nets in order to model round-robin scheduling easily. Some experimental results obtained by the proposed method are shown.[5] J-L. Roux and B. Berthomieu. Verification of a local area network protocol with tina, a software package for time petri nets. 7th European Workshop on Application and Theory of Petri Nets, pages 183-205, 1986.[6] T.

Model checking is a technique to decide whether a system modeled by a state graph satisfies a temporal logic formula. A serious problem in model checking of practical systems is that the size of the state graphs becomes huge. One solution of this problem is symbolic model checking, in which sets of states and transition relations over states are represented and handled symbolically. This research studies symbolic model checking in which realtime systems are modeled by time Petri nets and specifications are expressed by computation tree logic formulas. As realtime systems potentially have infinite state spaces, techniques to reduce infinite state spaces to finite ones are necessary. This paper discusses a technique based on equivalence classes, called regions, of states as well as a technique to restrict the behavior of time Petri nets so that transitions fire only at integer times. The algorithm in the former approach is presented in detail and then some experimental results are shown. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 3, 80(4): 11–20, 1997

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Pressure reducing valves are widely used to maintain the pressure of gas reservoirs to specific values. When highly pressurized air passes through the orifice structure, considerable noise occurs at the downstream side. To solve this problem, we have developed a radial slit structure. The radial slit structure reduces the noise by suppressing the generation of turbulence and shock wave at the downstream. In this paper, we newly develop a pressure reducing valve applied the concept of the slit structure. At the former slit structure, the height of the radial slit was fixed. In the new valve, we proposed an improved slit structure that the height of it is variable. Coned disk springs are installed between the disks and the height of it is controlled from 0 to 50m with a pneumatic cylinder. As a result, the new structure can successfully control the flow rate and control the pressure in a reservoir. The performance of the valve is investigated experimentally and confirmed that noise can be reduced with the radial slit structure.