| 释义 |
dihedral, a. and n. Cryst.|daɪˈhiːdrəl|
Also diedral.
[f. next + -al1: cf. F. dièdre in same sense.]
A. adj.
1. Having or contained by two planes or plane faces. dihedral angle, the inclination of two planes which meet at an edge. dihedral summit, a summit (of a crystal) terminating in a dihedral angle. spec. Aeronaut., designating the inclination, esp. upwards, of a wing or other surface to the horizontal, or the angle to the horizontal so formed; dihedral board, a device used in measuring the dihedral angle of the wings of an aeroplane.
1799G. Smith Laboratory I. 2 Terminating in dihedral pyramids. 1808Thomson in Phil. Trans. XCVIII. 69 Oxalate of potash..crystallizes in flat rhomboids..terminated by dihedral summits. 1826Henry Elem. Chem. I. 38 Variations of temperature produce a..difference in..a crystal of carbonate of lime..As the temperature increases, the obtuse dihedral angles diminish..so that its form approaches that of a cube. 1863–72Watts Dict. Chem. II. 124 [In the rhombic dodecahedron] The dihedral angles formed by the meeting of the faces are all equal to 120°. 1909Westm. Gaz. 11 Mar. 4/1 The problem of automatic transverse stability is solved by giving the aeroplanes a dihedral angle or keels. 1916H. Barber Aeroplane Speaks iii. 108 Another method of securing the dihedral angle..is by means of the dihedral board. 1917C. C. Turner Aircraft of To-Day viii. 140 Inherent stability is secured..by a dihedral setting of the wings, i.e. sloping up to right and left from the body. 1960C. H. Gibbs-Smith Aeroplane i. ix. 38 They had at first rigged it with a dihedral angle, and found it flew badly in gusty winds.
2. Math. Of the nature of a dihedron.
1893Harkness & Morley Theory of Functions 29 A simple dihedral configuration. 1893Forsyth Functions of a Complex Variable 625 Functions which are unaltered for the dihedral group of substitutions.
B. n. Aeronaut. A dihedral angle or inclination. Also transf.
1913A. E. Berriman Aviation iii. 37 The tail plane is invariably set at a lesser effective angle of incidence than the main wings. This arrangement is commonly described as the fore-and-aft dihedral. 1929W. Faulkner Sartoris v. 364 While in level flight, dihedral would be eliminated for speed. 1935C. G. Burge Complete Bk. Aviation 581/2 If the planes are inclined upwards towards the wing tips, the dihedral is positive; if downwards, it is negative. 1962Times 25 May 18/5 Michelotti has..lifted the dihedral of the wings [of a car], setting twin headlamps beneath. 1969J. M. Bruce War Planes of First World War III. 134 This aircraft differed from the first in having no dihedral on the lower wings. |