| 释义 |
attenuation|əˌtɛnjuːˈeɪʃən|
[ad. L. attenuātiōn-em, n. of action f. attenuāre to attenuate: see -ation. Cf. F. atténuation.]
The action of attenuating; attenuated condition.
1. The making thin or slender in transverse measure; diminution of thickness; emaciation.
a1631Donne Select. (1840) 265 Neither in a superfluous and cumbersome fatness, nor in an uncomely..attenuation. 1849Murchison Siluria iii. 60 The omissions of certain deposits in some parts, and their attenuation in others. 1870Disraeli Lothair vi. 20 His stature seemed magnified by the attenuation of his form.
2. The making less dense; diminution of density. spec. in brewing and distilling.
1594Plat Jewell-ho. i. 40 All those elements doo onely differ in attenuation and condensation. 1646Sir T. Browne Pseud. Ep. 159 Heat doth..rarifie that body [i.e. air], and by attenuation..disposeth it for expulsion. 1732Arbuthnot Rules of Diet 273 The Attenuation of the Aliment makes it perspirable. 1873Watts Fownes' Chem. 576 The diminished density, or attenuation of the wort. 1882W. T. Brannt tr. Thausing's Beer 707 The decrease in density [of the beer-worts] is called attenuation. 1956New Biol. XXI. 17 Beers..which are satisfactory in respect of attenuation.
3. The process of weakening, as if by dilution; diminution of characteristic force. spec. of a disease, or of the pathogenicity of a micro-organism. Also attrib.
1868M. Pattison Academ. Org. §5. 149 The process by which the results of philosophy are rendered popular is not one of attenuation but of translation. 1882Manch. Guard. 22 Sept. 5 The gradual ‘attenuation’ of disease germs. 1944C. D. Darlington in Nature 5 Aug. 167/1 In the attenuation process, the nucleus is mutafacient with respect to the virus. 1964M. Hynes Med. Bacteriol. (ed. 8) vi. 62 The virulence of a given organism can often be reduced by physical means such as drying or heat. The reduction of virulence is known as attenuation.
4. Electr. The decrease in amplitude of an electrical signal or current. Also attrib.
1887Heaviside in Electrician 24 June 143/2 The idea of attenuation, expressed in a more roundabout manner in terms such as diminution of amplitude, and so forth, is nothing new; the word ‘attenuation’ I found Lord Rayleigh use, and at once adopted it myself. 1931B.B.C. Year-Bk. 436/2 Attenuation Factor, a factor indicating the rate of reduction in amplitude of an ether wave as the distance from the point of origin increases. 1931Wireless World 2 Sept. 228/1 The attenuation of the higher modulation frequencies. 1935Discovery Sept. 278/2 The cut-off or attenuation of television signals, due to intervening obstructions. |