“principal axis”的概念、定义、翻译、参考文献-科学参考

单词	principal axis
释义	principal axis [`prin·sǝ·pǝl `ak·sǝs] ^{CRYSTALLOGRAPHY} The longest axis in a crystal. ^{ENGINEERING ACOUSTICS} A reference direction for angular coordinates used in describing the directional characteristics of a transducer; it is usually an axis of structural symmetry or the direction of maximum response. ^MATHEMATICS 1. One of a set of perpendicular axes such that a quadratic function can be written as a sum of squares of coordinates referred to these axes. 2. For a conic, a straight line that passes through the midpoints of all the chords perpendicular to it. 3. For a quadric surface, the intersection of two principal planes. ^MECHANICS One of three perpendicular axes in a rigid body such that the products of inertia about any two of them vanish. ^OPTICS See <<optic axis>>
随便看	ringlock nail ring micrometer ring modulator Ring Nebula ring network ring of operators ring-oil ring plain ring power transmission line ring road ring-roller mill ring-rolling ring rot rings and brushes ring shift ring sight ring silicate rings of Saturn ring spinner ring spot ring stress ring structure ring syncline ring system ringtail

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