| 释义 |
self-reˈversal
[self- 3 b.]
1. Reversal (of motion) by agency of the mover itself.
1886R. Wormell Electr. in Service of Man 61 This [induction] machine is exceedingly powerful in favourable weather, but has an important defect, in a tendency to self-reversal, which is apt to occur at a stoppage.
2. Physics. The darkening of the middle of a bright spectral line as a result of radiation emitted by a hot gas being partly reabsorbed as it passes through parts of the gas that are cooler.
1905E. C. C. Baly Spectroscopy xii. 384 The lines generally were sharper than in the case of the arc in air,..and there were fewer self-reversals. 1934H. E. White Introd. Atomic Spectra xiv. 250 The centers of the potassium-doublet, the calcium-singlet, and the copper-doublet lines show self-reversal due to absorption. 1977A. Corney Atomic & Laser Spectrosc. x. 313 Systematic errors are difficult to avoid in these experiments since the profile..is usually considerably distorted by self absorption or even self reversal.
3. Geol. The postulated reversal of the magnetization of some rocks by intrinsic means, rather than by reversal of the Earth's magnetic field (see quot. 1971).
1952T. Nagata et al. in Jrnl. Geomagnetism & Geoelectr. IV. 22 An experimental proof of self-reversal of thermo-remanent magnetism of igneous rocks is obtained. 1971Nature 5 Feb. 378/1 At this point [sc. the early 1950s] an alternative to field reversal began to receive serious consideration. This was self-reversal, the possibility that some rocks possessed an intrinsic property whereby they could acquire a magnetization antiparallel to the ambient field, or whereby an originally parallel magnetization could reverse spontaneously. |