No abstract

We propose a one-dimensional model of a superconducting link which is "weak" only insofar as it has a lower critical current than the superconductors on either side. According to appropriate solutions of the Ginzburg-Landau equations, the supercurrent J is a single-valued, odd function of the phase change cp across the link, which goes to zero at

\d) only insofar as it has a shorter mean free path l B and hence a larger penetration depth ^B...

The inverted state of a simple pendulum is a configuration of unstable equilibrium. This instability may be removed if the pivot is harmonically displaced up and down with appropriate frequency and amplitude. Numerical simulations are employed to investigate the stable domains of the system. The associated basins of attraction, extracted by interpolated cell mapping, are seen to be fractal. Loss of stability at high excitation amplitudes is observed to follow a Hopf bifurcation.

No abstract

Stable inverted states of a simple pendulum are possible when the pivot is subjected to high-frequency vertical oscillations. Such a pendulum has been constructed, and the ranges of displacement frequency and amplitude for which the inverted state is stable have been experimentally determined and compared to theoretical calculations.