Several transitions in the friction coefficient with increasing load are found on Au(111) in sulfuric acid electrolyte containing Cu ions when a monolayer (or submonolayer) of Cu is adsorbed. At the corresponding normal loads, a transition to double or multiple slips in stick-slip friction is observed. The stick length in this case corresponds to multiples of the lattice distance of the adsorbe...

For individuals with upper-extremity motor disabilities , the head-stick is a simple and intuitive means of performing manipulations because it provides direct proprioceptive information to the user. Through practice and use of inherent proprioceptive cues, users may become quite adept at using the head-stick for a number of diierent tasks. The traditional head-stick is limited, however, to the...

The theory of stick-slip is developed, based on the concept of a static and dynamic coefficient of friction. The dynamic coefficient is assumed to be independent of displacement and to depend wholly on normal stress across the surface. It is also assumed to be velocity-independent. The theory predicts that the stress drop during stick-slip is independent of machine stiffness. The displacement d...

The fluctuations in the vertical displacement angle of a stick balanced at the fingertip exhibit on-off intermitency. However, even a skilled balancer cannot indefinitely maintain a stick balanced at their fingertip. The survival function for stick balancing, P (tesc > t), is shown to have the form of a Weibul function, exp(−λt)β , where λ is a constant and β > 1. The measured survival function...