| 释义 |
▪ I. damping, vbl. n.|ˈdæmpɪŋ|
[-ing1.]
1. a. The action of the verb damp, q.v. Also attrib., as in damping-machine, damping-plate (= damper 3).
1756W. Toldervy Two Orphans III. 172 The flames, by slight damping, soon became the more violent. 1816J. Smith Panorama Sc. & Art II. 312 The bottom of the furnace..the holes of the damping plate. 1874Knight Dict. Mech., Damping-machine. 1. (Printing.) A machine for damping sheets of paper previous to printing..2. A machine in which starched goods are moistened previous to running them through the calendering-machine.
b. The action of damping an oscillation or an oscillating body (also damping out: see damp v. 1 c, d); the resistance to an oscillation; also, the amount of this, as measured by the rate at which the oscillation diminishes in amplitude.
1870Phil. Mag. XXXIX. 435 An oscillatory current..sustains itself twice as long against the damping action of resistance as a comparatively steady current of the same maximum value. 1874Ibid. XLVII. 296 The damping effect which the multiplier exerts on the swing of the needle. 1877Rayleigh Theory of Sound I. iii. 57 The vibrations of a tuning fork properly constructed and mounted are subject to very little damping. 1879Encycl. Brit. X. 51/1 By damping is meant the decrease of the extent of the oscillations of the galvanometer needle arising from the dissipation of energy through the resistance of the air, the action of currents induced in neighbouring metallic circuits, the viscosity of the suspension fibre, and so on. 1881[see damper 4]. 1883Atkinson tr. Ganot's Physics (ed. 11) 832 The greater the masses of metal, and the more closely they surround the magnet, the stronger is the damping. 1907J. Erskine-Murray Handbk. Wireless Telegr. i. 28 Damping or decrease of amplitude is due to two causes—firstly, to dissipation of energy, as heat, in the local circuits; secondly, to radiation. 1912Q. Rev. July 242 The damping-out of oscillations cannot be expected to be as rapid. 1945Electronic Engin. XVII. 455 Resulting in better damping of the receiver diaphragm and consequently suppression of the effects of resonance. 1958Van Nostrand's Scientific Encycl. (ed. 3) 476/2 The metal specimen is vibrated and the rate of damping-out of the vibrations observed. 1967Condon & Odishaw Handbk. Physics (ed. 2) ii. iii. 22/1 As the magnitude of the damping is increased, the rate of decay of the oscillations becomes greater..until..the motion becomes aperiodic and is said to be critically damped.
2. damping off, the collapse of seedlings or cuttings caused by any of several parasitic fungi and encouraged by excessive moisture in the plant's environment. (Cf. damp v. 6.)
1899G. Massee Text-bk. Plant Dis. 54 The term ‘damping off’ is applied to a disease of seedlings, characterised by the falling over and dying of the plantlets. 1928F. T. Brooks Plant Dis. i. 4 Parasitic attack of seedling plants at soil level often causes ‘damping off’. 1970Liebscher & Koehler tr. Fröhlich & Rodewald's Pests & Dis. Tropical Crops 293 Symptoms of damping-off appear in seedbeds. 1971Daily Colonist (Victoria, B.C.) 13 Mar. 38/4 The dreaded ‘damping-off’ disease, a soil-borne infection that attacks and rots the stems of small seedling plants just at soil level.
3. attrib., as (sense 1 b) damping capacity [tr. G. dämpfungsfähigkeit (O. Foeppl 1923)], the ability of a metal or other solid to absorb vibrational energy and dissipate it as heat; damping coefficient, constant, or factor, any number representing the degree to which an oscillation is damped, usu. defined as the reciprocal of the time in which the amplitude decreases by a factor e; damping winding = damper 4 b.
1931Proc. Amer. Soc. Testing Materials XXXI. ii. 157 Engineering materials..are able to dissipate energy without failure when subjected to cyclic stresses below the fatigue limit... This property is known as ‘mechanical hysteresis effect’, ‘internal friction’ (of solids), or ‘*damping capacity’. The latter nomenclature was proposed by O. Foeppl in 1923, who offered the following definition: ‘Damping Capacity’ is the amount of work dissipated into heat by a unit volume of the material during a completely reversed cycle of unit stress. This damping capacity is measured in inch-pounds per cubic inch per cycle. 1953S. P. Timoshenko Hist. Strength of Materials xii. 378 The damping capacity of metals and its relation to fatigue strength. 1959Chambers's Encycl. X. 326/2 Damping Capacity..is low in a sonorous metal such as bell-metal, and high in a ‘dead’ metal like lead.
1906J. A. Fleming Princ. Electr. Wave Telegr. i. 21 The Napierian logarithm of the ratio of any maximum current or ordinate to the next maximum in the opposite direction multiplied by twice the frequency, gives us the value of the *damping coefficient. 1929W. E. Dalby Balancing of Engines (ed. 4) viii. 259 The damping coefficients derived from the dynamic magnifier are more likely to approximate to the damping of the loaded bridge than damping coefficients determined from the residual oscillations.
1922F. F. Fowle Stand. Handbk. Electr. Engineers (ed. 5) xxiv. 1963 The *damping constant of a circuit is a measure of the ratio of the dissipative to the reactive component of its admittance or impedance.
1906J. A. Fleming Princ. Electr. Wave Telegr. iii. 162 The *damping factor a is a quantity the dimensions of which are those of the reciprocal of a time, whilst the logarithmic decrement is a mere numeric.
1920Whittaker's Electr. Engineer's Pocket-Bk. (ed. 4) 224 *Damping windings are also fitted on synchronous generators..to damp out pulsations due to variations in the armature ampere-turns.
▪ II. damping, ppl. a.|ˈdæmpɪŋ|
[-ing2.]
That damps, in various senses: see damp v.
1607T. Walkington Opt. Glass 28 The damping fumes that the Sun elevates from bogges. 1691–8Norris Pract. Disc. 151 What a damping Thought must it be for such a Man to consider [etc.]. 1844Dickens Mart. Chuz. xiii, It was somewhat of a damping circumstance to find the room full of smoke. 1878M. C. Jackson Chaperon's Cares I. xi. 153 Clarissa's presence generally has a slightly damping effect upon Forster. 1928S. P. Timoshenko Vibration Probl. Engin. i. 22 These damping forces may arise from several different sources, such as air or fluid friction, internal friction of the material of the vibrating body, or friction between sliding surfaces. 1936W. Heitler Quantum Theory of Radiation i. 34 But because of the damping force the amplitude of the oscillator will decrease. 1958C. G. Wilson Electr. & Magn. v. 137 These oscillations cease when all the energy of the coil is dissipated in overcoming the damping forces present. |