| 释义 |
▪ I. truncate, a.|ˈtrʌŋkeɪt|
[ad. L. truncāt-us, pa. pple. of truncāre: see truncate v.]
†1. Cut short, mutilated. Obs. (exc. as in 2).
1579–83[implied in truncately].
2. In scientific and technical use: = truncated 2.
1716E. Halley in Phil. Trans. XXIX. 408 Like truncate Cones or Cylinders. 1785Martyn Rousseau's Bot. xxi. 305 The Tulip Tree..is remarkable for the shape of its leaves, having the middle lobe of the three truncate, or cut transversely at the end. 1826Kirby & Sp. Entomol. IV. xlvi. 333 Elytra..Truncate... When they are shorter than the abdomen and transverse at the end. 1839Darwin Voy. Nat. i. (1879) 2 Successive steps of tableland, interspersed with some truncate conical hills [i.e. kopjes]. 1872Coues N. Amer. Birds 38 A rectrix broad to the very tip, and there cut squarely off, is truncate.
b. In combination with another adj. of form, as truncate-turbinate; = truncato-.
1887W. Phillips Brit. Discomycetes 354 Cups substipitate, truncate-turbinate.
▪ II. truncate, v.|ˈtrʌŋkeɪt, trʌŋˈkeɪt|
[f. L. truncāt-, ppl. stem of truncāre, f. truncus trunk.]
a. trans. To shorten or diminish by cutting off a part; to cut short; to maim, mutilate. Also fig.
1486,1572[implied in truncated 1]. 1727Bailey vol. II, Truncate, to cut shorter, to maim. 1755Johnson Dict. Pref. ⁋70 The examples are too often injudiciously truncated. 1852W. R. Williams Relig. Progr. iii. (1854) 53 It wrongs man by truncating his nature of conscience and immortality. 1911Athenæum 16 Sept. 318/2 He..never wrote short stories, only truncated long ones.
b. In scientific and technical use: spec. in Cryst. to ‘cut off’ or replace (an edge or solid angle) by a plane face, esp. so as to make equal angles with the adjacent faces. Chiefly in pa. pple.: see truncated 2.
1758Reid tr. Macquer's Chem. I. 97 Pyramids..some of which..are obtuse as if truncated. 1830Lyell Princ. Geol. I. 393 If this gulf were..choked up,..so that new explosions..should truncate the cone once more. 1883Encycl. Brit. XVI. 348/1 The faces of one hexagonal prism would truncate the lateral edges of the rhombohedron, while the faces of the other..would truncate its lateral solid angles.
c. Math. To cut short or approximate (a series, etc.) by ignoring all the terms beyond a chosen term. Also absol.
1955M. Loève Probability Theory xvi. 233 We truncate X [sc. a random variable] at c > 0..when we replace X by Xc = X or 0 according as {vb}X{vb} ‹ c or {vb}X{vb} ≥ c. 1966J. H. Cadwell Topics Recr. Math. xiv. 157 Because of the steadily decreasing terms, when the series is truncated the error incurred is of smaller magnitude than the first term omitted. 1968P. A. P. Moran Introd. Probability Theory ii. 78 It is also sometimes useful to exclude more than one of the possible values of i, and in this case it is more often necessary to truncate at the other end. 1981Nature 5 Nov. 14/3 The series in equation (1) should extend to m = n = ∞, but in practice the series is truncated at a maximum value..of m and n, usually in the range 8 to 15.
Hence truncating ppl. a., that truncates; spec. said of a plane that replaces an edge or solid angle.
1805–17R. Jameson Char. Min. (ed. 3) 118 These new planes are named Truncating Planes, and the edges which they form with the other planes Truncating Edges. 1882Ruskin Bible of Amiens iii. 95 These two truncating and guarding rivers. |