| 释义 |
▪ I. ˈcross-ˈsection, n.
Also cross section.
1. a. The cutting of anything across; a section made by a plane cutting anything transversely. spec. = section n. 4 a.
1835A. Gray Lett. (1893) I. 52 A cross-section shows the same structure as the rattan. 1870Spon's Dict. Engin. II. 389 A front elevation and cross-section of a boiler. 1874Ibid. VIII. 2924 The converting department, shown in ground plan by Fig. 6996, and in cross-section by Fig. 6998. 1878J. H. Beadle Western Wilds x. 143 Five men were twenty days felling it, the object being to have it sawed into cross-sections to be shipped eastward to Europe. 1884Bower & Scott De Bary's Phaner. 323 The characteristic habit of most Monocotyledonous bundles, which is especially evident in cross-section. 1884tr. Lotze's Logic 265 It is only necessary that the mass be the same at any cross-section of this material line. 1933Archit. Rev. LXXIV. 123 This pictorial cross-section.
b. fig. A typical or representative sample, group, etc., or an examination of this.
1903Independent 22 Jan. 210/2 A narrow, timorous artificial treatment of some such limited subject or ‘cross-section’ of a subject as may be represented ‘concretely’. 1904Kipling Traffics & Discov. 322 Cross-sections of remote and incomprehensible lives. 1909H. G. Wells Tono-Bungay i. i. 5 You will ask by what merit I achieved this remarkable social range, this extensive cross-section of the British social organism. 1938Ann. Reg. 1937 275 The New York Annalist's index of business activity, covering a wide cross-section of statistically measurable activity. 1952E. Grierson Reputation for Song xxvi. 222 The jury, a fair cross-section of the community.
2. Physics. Used of the apparent area (measured in barns or millibarns) of a nucleus, atom, elementary particle, etc., as representing the probability of a specified interaction with another particle, etc. Symbol σ.
1921Sci. Abstr. A. XXIV. 393 A method is described whereby the effective cross section of gas molecules is determined by means of slowly-moving electrons having a definite single velocity and definite path. 1938R. W. Lawson tr. Hevesy & Paneth's Man. Radioactivity (ed. 2) vii. 75 The effective cross-section is equal to the mass absorption coefficient divided by 6 × 1023, and multiplied by the atomic weight. 1955R. D. Evans Atomic Nucleus 826 In the wave or field model, the ‘cross section’ for a particular interaction is the ratio between the rate of energy removal (power) and the incident intensity (power per unit area) per target particle. The cross section can be visualized as an area in the incident wave front... In the corpuscular model, the ‘cross section’ is the fraction of the incident particles which suffer the specified interaction, divided by the number of target particles per unit area of a thin target. 1960Gloss. Atomic Terms (H.M.S.O.) 16 Cross section, the apparent size of a nucleus. This varies for many nuclei according to the reaction occurring (capture, fission or scattering) and the speed of the oncoming particle. 1962Gloss. Terms Nucl. Sci. (B.S.I.) 30 Cross section, of a given nucleus or atom for a given radiation, that area perpendicular to the direction of the radiation which one has to attribute to the nucleus or atom to account geometrically for its interaction with the radiation; or, in other words, the number of those interactions per unit time divided by the radiation flux and the number of nuclei or atoms present. 1967Condon & Odishaw Handbk. Physics (ed. 2) ix. viii. 214/2 The intrinsic probability that a reaction will occur is measured by its cross section... All conceivable events that occur when a projectile strikes a nucleus have their separate cross sections. One speaks of the cross section for elastic scattering,..for absorption,..etc. 1971Nature 23 Apr. 523/2 Other processes, such as the 16O(n,α)13C reaction, may contribute to the more point-like flashes, but their cross-sections are generally small.
▪ II. ˈcross-ˌsection, v.
[f. the n.]
trans. To make a cross-section of; to cut into cross-sections. Hence ˌcross-ˈsectioning vbl. n.
1876Van Nostrand's Eclectic Engin. Mag. XIV. 394/1 The engineer should have an intimate knowledge of the ground on the line of the work. This is obtained by means of cross-levels taken at right angles to the reference line of the work... This work in engineering parlance is cross-sectioning. Ibid. 399/2 The finished work can be cross-sectioned and plotted in the same manner as the original ground. 1890L. D'Oyle Notches 52 They were going down to ‘cross-section’ the old railway survey which ran through our valley. 1897Outing (U.S.) XXX. 126/2 Much of the ground is..conveniently bounded and cross-sectioned by roads. 1908Westm. Gaz. 22 Aug. 14/1 The eye would then cross-section its words, reading the lateral parts in indirect vision. |