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The impact of autonomous vehicles on the spatial size of cities remains ambiguous, as the future is highly uncertain. This paper uses counterfactual analysis techniques to examine the effects of autonomous vehicles on urban expansion for metropolitan areas in the United States if autonomous vehicles had been introduced before. We argue that distance cost and congestion cost, which are the two components of transportation cost with different effects on urban expansion, should be addressed in autonomous vehicle research. By coupling historical data with hypothetical scenarios of introducing autonomous vehicles to cities, we find that urban expansion, rather than urban densification, would have been the dominant effect if autonomous vehicles had been introduced into cities. The finding indicates that if autonomous vehicles are widely adopted in the future, they are likely to have similar, or even larger, effects on future urban expansion than in the counterfactual past. [ABSTRACT FROM AUTHOR]

A dynamic current model for the double gate negative capacitance field-effect transistor (NCFET) of the metal–ferroelectric–insulator–semiconductor (MFIS) structure is presented in this work. With a damping parameter ρ in the Landau–Khalatnikov (LK) theory for general ferroelectric (FE) materials, the gate control equation of NCFET is intrinsically dynamic which is solved directly as a basis of NCFET modeling. With the time-dependent charge densities at the source and drain sides, a dynamic current model is formulated analytically for the first time, considering the dynamic terms in a self-consistent way. The model has been verified with numerical TCAD simulations. It accurately reproduces the static negative capacitance (NC) effect in enhancing the driving current, as well as the dynamic NC effect, in the conduction delay and hysteresis for a wide range of NCFET parameters. The dynamic model after implementations is successfully applied to circuit simulations such as ring oscillators without convergence issues. [ABSTRACT FROM AUTHOR]