| 单词 |
polytropic |
| 释义 |
polytropic, a.|pɒlɪˈtrɒpɪk|
[f. Gr. πολύτροπος turning many ways, versatile, etc., also much-travelled (epithet of Ulysses in the Odyssey), f. πολυ-, poly- + τρόπος turn.]
1. Capable of turning to various courses or expedients; versatile.
1838Fraser's Mag. XVII. 506 In the Odyssey..his polytrophic powers are brought into full play. 1862Temple Bar Mag. VI. 243 We may encounter men in that city who are as polytropic as Ulysses.
2. Math. Turning several times round a pole; also applied to a function which has several different values for one of the variable (opp. to monotropic).
3. [ad. G. polytrope (E. Loew 1884, in Jahrbuch K. Bot. Gartens Berlin).] Of a bee: collecting nectar from many kinds of flower.
1899C. Robertson in Bot. Gaz. XXVIII. 29 If a bee has a long flight it must be regarded as polytropic. 1919J. H. Lovell Flower & Bee 120 There are also on the wing at the same time 6 species which are polytropic.
4. Physics and Astr. [ad. G. polytropisch (G. Zeuner Technische Thermodynamik (ed. 3, 1887) I. xxix. 143).] Pertaining to or designating a body of gas or a process in which pressure and volume change in such a way that a specific heat remains constant. Also as n., a graph showing such a variation of pressure and volume.
1907J. F. Klein tr. Zeuner's Technical Thermodynamics I. xxix. 152 If the initial condition is given by p1 and v1, we accordingly have pvn= p1v1n..as the equation of the sought pressure curve, which we will hereafter call the polytropic curve. 1926A. S. Eddington Internal Constitution of Stars iv. 94 A class of problems arises in which the polytropic condition..applies only to part of the star. 1933Monthly Notices R. Astron. Soc. XCIII. 390 Emden's well-known researches on the equilibrium of polytropic gas spheres has been of fundamental importance in its repercussions on the modern theories of stellar structure. 1939S. Chandrasekhar Introd. Study Stellar Struct. ii. 40 An adiabatic..is a polytropic of zero specific heat, and an isothermal a polytropic of infinite heat capacity. 1952W. M. Deans tr. Prandtl's Essent. Fluid Dynamics v. 391 If we assume a polytropic law for the variation of density with height, P/Pg = (ρ/ρg)n, where the suffix g refers to the ground. 1968Cox & Giuli Princ. Stellar Struct. II. xxiii. 703 A polytropic star is one which obeys an equation of the form P = Kρ(n + 1)/n, where n, the polytropic index..and κ are constants throughout the star. 1976Nature 17 June 561/1 The moment of inertia of a spherical star can be written I = kmpNR2 where for stable polytropic stars 0·04{slle}k{slle}0·132. |
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