Champ électromagnétiqueUn champ électromagnétique ou Champ EM (en anglais, electromagnetic field ou EMF) est la représentation dans l'espace de la force électromagnétique qu'exercent des particules chargées. Concept important de l'électromagnétisme, ce champ représente l'ensemble des composantes de la force électromagnétique s'appliquant sur une particule chargée se déplaçant dans un référentiel galiléen. Une particule de charge q et de vecteur vitesse subit une force qui s'exprime par : où est le champ électrique et est le champ magnétique.
Ferrite coreIn electronics, a ferrite core is a type of magnetic core made of ferrite on which the windings of electric transformers and other wound components such as inductors are formed. It is used for its properties of high magnetic permeability coupled with low electrical conductivity (which helps prevent eddy currents). Moreover, because of their comparatively low losses at high frequencies, they are extensively used in the cores of RF transformers and inductors in applications such as switched-mode power supplies, and ferrite loopstick antennas for AM radio receivers.
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.
Diatonic and chromaticDiatonic and chromatic are terms in music theory that are most often used to characterize scales, and are also applied to musical instruments, intervals, chords, notes, musical styles, and kinds of harmony. They are very often used as a pair, especially when applied to contrasting features of the common practice music of the period 1600–1900. These terms may mean different things in different contexts. Very often, diatonic refers to musical elements derived from the modes and transpositions of the "white note scale" C–D–E–F–G–A–B.
ChromaticismChromaticism is a compositional technique interspersing the primary diatonic pitches and chords with other pitches of the chromatic scale. In simple terms, within each octave, diatonic music uses only seven different notes, rather than the twelve available on a standard piano keyboard. Music is chromatic when it uses more than just these seven notes. Chromaticism is in contrast or addition to tonality or diatonicism and modality (the major and minor, or "white key", scales).
Approximation de GaussL'approximation de Gauss nommée d'après le physicien allemand Carl Friedrich Gauss, est l'approximation linéaire de l'optique géométrique obtenue dans certaines conditions appelées conditions de Gauss. Cette approximation, souvent applicable en pratique, permet de simplifier les relations mathématiques de l'optique géométrique. On obtient dans ces conditions un stigmatisme approché. Les écarts à cette approximation rencontrés dans les instruments d'optique sont appelés aberrations géométriques.
Acyclic coloringIn graph theory, an acyclic coloring is a (proper) vertex coloring in which every 2-chromatic subgraph is acyclic. The acyclic chromatic number A(G) of a graph G is the fewest colors needed in any acyclic coloring of G. Acyclic coloring is often associated with graphs embedded on non-plane surfaces. A(G) ≤ 2 if and only if G is acyclic. Bounds on A(G) in terms of Δ(G), the maximum degree of G, include the following: A(G) ≤ 4 if Δ(G) = 3. A(G) ≤ 5 if Δ(G) = 4. A(G) ≤ 7 if Δ(G) = 5. A(G) ≤ 12 if Δ(G) = 6.
Nombre d'AbbeEn optique, et plus particulièrement en lunetterie, le nombre d'Abbe, constringence ou coefficient de dispersion d'un verre optique sert à en déterminer la dispersion, c'est-à-dire la variation de l'indice de réfraction avec la longueur d'onde. Il quantifie l'aberration chromatique transversale d'une optique. Le nom a été donné en l'honneur du physicien Ernst Abbe qui a défini la constringence.
