| 释义 |
decrement|ˈdɛkrɪmənt|
[ad. L. dēcrēment-um, f. dēcrē- stem of inceptive dēcrē-sc-ĕre to decrease: see -ment.]
1. a. The process or fact of decreasing or growing gradually less, or (with pl.) an instance of this; decrease, diminution, lessening, waste, loss. (Opposed to increment.)
1621Mountagu Diatribæ 310 The decrements of the First-fruits. 1631R. Brathwait Whimzies 93 Hee would finde his decrements great, his increments small: his receits come farre short of his disbursements. 1660Boyle New Exp. Phys. Mech. xxi. 151 The greater decrement of the pressure of the Air. 1695Woodward Nat. Hist. Earth v. (1723) 253 Rocks..suffer a continual Decrement, and grow lower and lower. 1774J. Bryant Mythology I. 339 A society..where there is a continual decrement. 1840J. H. Green Vital Dynamics 81 Signs of the decrement of vital energy.
†b. spec. Bodily decay, wasting away. Obs.
1646Sir T. Browne Pseud. Ep. vi. iv. 289 Our decrement accelerates, we set apace, and in our last dayes precipitate into our graves. 1692Ray Dissol. World iii. v. (1732) 340 There is a Decrement or Decay both of Things and Men.
c. The wane (of the moon): spec. in Heraldry.
1610J. Guillim Heraldry iii. iii. (1611) 91 Her divers denominations in Heraldrie, as her increment in her increase..her decrement in her waning and her detriment in her change and eclipse. 1822T. Taylor Apuleius 292 The Moon..defining the month through her increments, and afterwards by her equal decrements.
d. decrement of life: in the doctrine of annuities and tables of mortality: The (annual) decrease of a given number of persons by death.
1752Phil. Trans. XLVII. liii. 335 The decrements of life may be esteemed nearly equal, after a certain age. 1755Brakenridge ibid. XLIX. 180 It will be easy to form a table of the decrements of life. 1851Herschel Stud. Nat. Phil. ii. vi. 178 The decrement of life, or the law of mortality.
e. Cryst. ‘A successive diminution of the layers of molecules, applied to the faces of the primitive form, by which the secondary forms are supposed to be produced’ (Webster).
1805–17R. Jameson Char. Min. (ed. 3) 146 The decrements on the edges concur with those in the angles to produce the same crystalline form. 1823H. J. Brooke Introd. Crystallogr. 18 When the additions do not cover the whole surface of a primary form, but there are rows of molecules omitted on the edges, or angles or the superimposed plates, such omission is called a decrement. 1858Buckle Civiliz. II. vii. 402 The secondary forms of all crystals are derived from their primary forms by a regular process of decrement.
2. a. The amount lost by diminution or waste; spec. in Math. a small quantity by which a variable diminishes (e.g. in a given small time).
1666Boyle Orig. Formes & Qual., [What] the obtained powder amounts to over and above the decrement of weight. 1758I. Lyons Fluxions 90 Let υ be the decrement of y. 1812–6Playfair Nat. Phil. (1819) I. 227 The decrements of heat in each second. 1846H. Rogers Ess. (1860) I. 202 Admitting increase or diminution by infinitely small increments or decrements. 1883Economist 15 Sept., If the unearned increment is to be appropriated by the State..The undeserved decrement, as perhaps it may be called, would surely claim compensation.
b. The ratio of the amplitudes of two successive cycles of a damped oscillation; also (more fully logarithmic decrement), the natural logarithm of this.
1879Encycl. Brit. X. 50/1 Such needles have great advantages—where, for instance, the time of oscillation, the logarithmic decrement, or the extent of swing of the needle has to be observed. 1908E. H. Barton Text-bk. Sound x. 577 Hartmann-Kempf found that the relation between logarithmic decrement and amplitude for three makes of tuning-fork is almost linear. 1913[see decremeter]. 1927E. G. Richardson Sound iv. 121 To estimate the rate of decay, the ratio of the amplitudes in two successive periods is obtained, a quantity which is known as the decrement. It is the logarithm of this quantity..which usually figures in calculations. 1929J. A. Ratcliffe Physical Principles of Wireless i. 14 The reciprocal of this quantity, R√ c / l , is of great importance in the theory of oscillatory circuits; it is known as the decrement of the circuit, and corresponds to the logarithmic decrement of a mechanical oscillatory system. 1936L. S. Palmer Wireless Engin. iii. 47 Circuits with small decrements have good selectivity. 1966W. T. Thomson Vibration Theory ii. 48 A body vibrating in a viscous medium has a period of 0·20 sec. and an initial amplitude of 1·0 in. Determine the logarithmic decrement if the amplitude after 10 cycles is 0·02 in.
†3. Applied to certain college expenses at Oxford: see quot. 1726. Obs.
[1483in Arnolde Chron. (1811) 271 Item in decrementis, iij. li, vij. s'. i. d'.] 1726R. Newton in Reminiscences (Oxf. Hist. Soc.) 64 Decrements, each Scholar's proportion for Fuel, Candles, Salt, and other common necessaries: originally so call'd as so much did, on these accounts, decrescere, or was discounted from a Scholar's Endowment. |