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
Conceptual metaphor Aristotle is often situated as the first commentator on the nature of metaphor, writing in the "Poetics", "A 'metaphorical term' involves the transferred use of a term that properly belongs to something else," and elsewhere in the "Rhetoric" he says that metaphors make learning pleasant; "To learn easily is naturally pleasant to all people, and words signify something, so whatever words create knowledge in us are the pleasantest." Aristotle's writings on metaphor constitute a "substitution view" of metaphor, wherein a metaphor is simply a decorative word or phrase substituted for a more ordinary one. This has been sometimes called the