This paper reports theoretical and experimental studies on spatio-temporal dynamics in the choruses of male Japanese tree frogs. First, we theoretically model their calling times and positions as a system of coupled mobile oscillators. Numerical simulation of the model as well as calculation of the order parameters show that the spatio-temporal dynamics exhibits bistability between two-cluster antisynchronization and wavy antisynchronization, by assuming that the frogs are attracted to the edge of a simple circular breeding site. Second, we change the shape of the breeding site from the circle to rectangles including a straight line, and evaluate the stability of two-cluster and wavy antisynchronization. Numerical simulation shows that two-cluster antisynchronization is more frequently observed than wavy antisynchronization. Finally, we recorded frog choruses at an actual paddy field using our sound-imaging method. Analysis of the video demonstrated a consistent result with the aforementioned simulation: namely, two-cluster antisynchronization was more frequently realized.

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Bias temperature instability (BTI) is the dominant source of aging in nanoscale transistors. Recent works show the role of charge trapping/de-trapping (T-D) in BTI through discrete V th shifts, with the degradation exhibiting an excessive amount of randomness. Furthermore, modern circuits employ dynamic voltage scaling (DVS) where V dd is tuned, complicating the aging effect. It becomes challenging to predict long-term aging in an actual circuit under statistical variation and DVS. To accurately predict the degradation in these circumstances, this work (1 ) examines the principles of T-D, thereby proposing static and cycle-to-cycle (dynamic) models under voltage tuning in DVS; (2) presents a long-term model, estimating a tight upper bound of dynamic aging;(3) comprehensively validates the new set of models with 65nm silicon data. The proposed aging models accurately capture the recovery behavior in dynamic operations, reducing the unnecessary margin and enhancing the simulation efficiency for aging estimation during the design stage. Keywords-Trapping/de-trapping, statistical variations, compact modeling, negative bias temperature instability, DVS.I.