Submitted to Computer Aided Verification 98 Category A (practical techniques) Verification of Asynchronous circuits based on

Asynchronous circuits, which have no global clocks and work based on the causality relation between signal transitions, potentially have the advantages of high performance and low power dissipation. However, the state spaces of asynchronous circuits are often huge, because unlike synchronous circuits every wire has states. Thus, the formal verification of asynchronous circuits is more difficult than that of synchronous ones. In this paper, in order to reduce the computational cost of the verification, we propose implementing the trace theoretic verification by using Zero-Suppressed BDDs. The paper also shows several techniques for the performance improvement such as modeling circuits by Petri nets with inhibitor arcs, composing circuit components that do not cause safety failure, and using special ZBDD operations for Petri nets. Finally, we show some experimental results.

Experimental evaluation of Marangoni stress and surfactant concentration at interface of contaminated single spherical drop using spatiotemporal filter velocimetry

Spatiotemporal filter velocimetry (SFV) was extended to Lagrangian measurements with boundary-fitted measurement areas, and was applied to flows about single spherical drops of glycerol-water solution falling in stagnant silicon oil under clean and contaminated conditions to examine its applicability to the estimation of the Marangoni stress and surfactant concentration at a moving interface. Effects of bulk concentration of surfactant on the velocity field, the Marangoni stress and the surface concentration of surfactant were discussed from the measured data. As a result, we confirmed that accurate velocity distribution in the vicinity of the interface measured by SFV enables us to evaluate interfacial velocity and interfacial shear stresses and to estimate the Marangoni stress, interfacial tension and surfactant concentration at the interface with the assumption of negligible surface viscosity. The flow inside the drop and the interfacial velocity become weak due to the Marangoni stress caused by the gradient of surfactant concentration at the interface as the bulk concentration of surfactant increases. These results demonstrate that SFV is of great use in experimental analysis of adsorption and desorption kinetics at a moving interface