| 释义 |
Langevin, n. Math. and Physics.|ˈlɑ̃ʒəvæ̃|
[The name of Paul Langevin (1872–1946), French physicist.]
Used attrib. and in the possessive to designate concepts invented by Langevin or arising out of his work, as Langevin('s) equation, formula, (a) the general differential equation governing the Brownian motion of a free particle; (b) any of several expressions for magnetic susceptibility formulated by Langevin; Langevin function, the function coth x - 1/x , usu. denoted by {scrL}(x) .
[1937F. Bitter Introd. Ferromagnetism ii. 31 The function (coth a-1/a) is sometimes written L(a) , after Langevin, who first performed the derivation that led to it.] 1943Rev. Mod. Physics XV. 20 The modern theory of the Brownian motion of a free particle (i.e. in the absence of an external field of force) generally starts with Langevin's equation du/dt = - βu + A(t) , where u denotes the velocity of the particle. 1951R. M. Bozorth Ferromagnetism x. 458 The foregoing equation, known as Langevin's equation of diamagnetism, is applicable to all atoms. 1960Reitz & Milford Found. Electromagn. Theory v. 100 Equation (5–19) then yields: 〈p0 cos θ〉 = p0 [coth y - 1/y] , which is known as the Langevin formula. Ibid. xi. 222 For a material composed entirely of one molecular species, each molecule having magnetic moment m0, the fractional orientation is given approximately by the Langevin function. 1962Corson & Lorrain Introd. Electromagn. Fields iii. 109 The Langevin equation..was first derived by Langevin in 1905 for magnetic dipoles. 1974Jrnl. Chem. Physics LXI. 4242/2 To reduce the atom-chain scattering to a two-body collision process involving the incident atom and an effective single harmonic oscillator..we first develop a generalized Langevin equation governing the motion of the effective oscillator. 1985J. J. Becker in R. M. Besançon Encycl. Physics (ed. 3) 684/1 In the classical theory of paramagnetism, the orientations of the moments are considered to be initially thermally randomized in space. An applied field produces a net magnetic moment in its direction, as described by the classical Langevin function. 1988Nature 9 June 496/3 ‘Langevin’ equations..model the fluctuations of the polarization..and the laser electric field about their mean values. |