Tune shift with amplitude of the system. When the tune reaches resonant values, it can be unstable, and thus a tune-shift with amplitude can limit the stability region, or dynamic aperture. In classical mechanics, a simple example of a system with tune shift with amplitude is a pendulum. In accelerator physics, both the transverse and the longitudinal dynamics show tune shift with amplitude. A simple model of the transverse dynamics is of an oscillator with a single sextupole, it is referred to as the Hénon map. Another model for this case is the Standard Map. An important example is the typical case of distributed
Interface metaphor to making it resemble something the users understand. Experts, on the other hand, understand what is going on with the technical aspects of an interface metaphor. They know what they want to do and they know how to do it—and so they design shortcuts to facilitate achieving their goals. While the concept behind interface metaphors appears simple (to promote more efficient facilitation of a computer), a lack of empirical evidence exists to support these claims. Little research has actually been completed that demonstrates the benefits of implementing metaphors in computer systems as well as what makes a metaphor most effective.