Inverse magnetostrictive effectThe inverse magnetostrictive effect, magnetoelastic effect or Villari effect, after its discoverer Emilio Villari, is the change of the magnetic susceptibility of a material when subjected to a mechanical stress. The magnetostriction characterizes the shape change of a ferromagnetic material during magnetization, whereas the inverse magnetostrictive effect characterizes the change of sample magnetization (for given magnetizing field strength ) when mechanical stresses are applied to the sample.
RétrodiffusionLa rétrodiffusion est la partie de la diffusion d'ondes, de particules ou de signaux vers leur direction d'origine. Il s'agit généralement d'une réflexion diffuse, par opposition à une réflexion spéculaire provenant d'un miroir, bien qu'une rétrodiffusion spéculaire puisse se produire à incidence normale avec une surface. La rétrodiffusion a des applications importantes en astronomie, en photographie, en radar et en échographie médicale.
Particle in a ringIn quantum mechanics, the case of a particle in a one-dimensional ring is similar to the particle in a box. The Schrödinger equation for a free particle which is restricted to a ring (technically, whose configuration space is the circle ) is Using polar coordinates on the 1-dimensional ring of radius R, the wave function depends only on the angular coordinate, and so Requiring that the wave function be periodic in with a period (from the demand that the wave functions be single-valued functions on the circle), and that they be normalized leads to the conditions and Under these conditions, the solution to the Schrödinger equation is given by The energy eigenvalues are quantized because of the periodic boundary conditions, and they are required to satisfy or The eigenfunction and eigenenergies are where Therefore, there are two degenerate quantum states for every value of (corresponding to ).
