| 释义 |
trochoid, n. and a.|ˈtrɒkɔɪd, ˈtrəʊkɔɪd|
[ad. Gr. τροχοειδής round like a wheel, f. τροχός wheel + εἶδος form: see -oid; cf. F. trochoïde (1658 in Hatz.-Darm.).]
A. n.
1. Geom. A curve traced by a point on or connected with a rolling circle; orig. = cycloid 1: now usually restricted to the curtate and prolate cycloids, traced respectively by points within and without the circle; also extended to curves similarly generated by a circle rolling upon another circle, either inside it (hypotrochoid) or outside it (epitrochoid).
1704J. Harris Lex. Techn. I. s.v., A Curve Line..called a Cycloid or Trochoid. 1711W. Sutherland Shipbuild. Assist. 59 The Cycloids or Trochoids. 1867Denison Astron. without Math. 86 note, That curve is called a trochoid, but when the tracing point is on the circumference it becomes a cycloid. 1881C. W. Bourne in Eng. Mech. No. 874. 377/1 The bar AB is jointed to a bar BC, so that while AB revolves round A as centre, BC can also revolve round B as centre, then a curve will be described by the point C... Every such curve is comprised under the name ‘trochoid’.
2. Zool. A gastropod of the family Trochidæ; a top-shell.
1839Penny Cycl. XIV. 317/2 Mollusca... Class III. Gastropoda... Order 6. Pectinibranchiata. Family of Trochöids.
3. Anat. A trochoid articulation, a pivot-joint.
1860in Worcester; hence in later Dicts. [Cf. quot. 1857 in B. 3.]
B. adj.
1. Geom. = trochoidal 1. rare—0.
1882Ogilvie (Annandale), Trochoid, a. i. Trochoidal.
2. Conch. Top-shaped, conical with flat base, as the shells of the genus Trochus or family Trochidæ; Zool., belonging to the family Trochidæ.
1859J. R. Greene Man. Anim. Kingd., Protozoa 16 If..the spiral passes obliquely round an axis, the shell assumes a more or less pyramidal form, and is termed ‘trochoid’. 1861P. P. Carpenter in Rep. Smithsonian Instit. 1860, 213 The..African group Collonia have small Trochoid shells.
3. Anat. Applied to a pivot-joint, in which one bone turns upon another with a rotary motion.
1857Dunglison Med. Lex., Trochoid.., an articulation, in which one bone turns upon another, like a wheel upon its axle. 1860Mayne Expos. Lex., Trochoides,..resembling a wheel: trochoid. Anat. Applied to a movable connexion of bones in which one bone rotates upon another, as the first cervical vertebra upon the odontoid process of the second. |