| 释义 |
▪ I. impact, n.|ˈɪmpækt|
[ad. L. type *impact-us n., f. ppl. stem of impingĕre to impinge. Cf. mod.F. impact.]
1. a. The act of impinging; the striking of one body against another; collision. Chiefly in Dynamics, in reference to momentum.
1781Bp. Watson Chem. Ess. (1784) I. 165 note, The same rule, by which common velocity of hard or non-elastic bodies after their impact..is calculated. 1795Southey Joan of Arc viii. 228 The English chief, Pointing again his arbalist, let loose The string; the quarrel, by that impact driven, True to its aim, fled fatal. 1862Times 7 Mar., No such satisfactory results in the way of resisting the tremendous impact of the shot have been obtained from any other target. 1863Tyndall Heat ii. §56 The impact of atoms of oxygen against atoms of sulphur. 1866Huxley Phys. ix. (1872) 221 The impact of the vibrations of the luminous ether on the retina.
attrib.1878Stewart & Tait Unseen Univ. iv. 146 We are..driven to the impact theory as the only tenable one.
b. fig. Now commonly the effective action of one thing or person upon another; the effect of such action; influence; impression. Esp. in phr. to make an impact (on).
1817Coleridge Biog. Lit. 63 In any given perception there is a something which has been communicated to it [the mind] by an impact, or an impression ab extra. 1874Stubbs Const. Hist. I. i. 7 The impact of barbarian conquest split up the unity of the Latin tongue. 1946Sat. Rev. Lit. (U.S.) 28 Dec. 15/1 The impact of the images, their skilful juxtaposition, and the bold page lay⁓outs make words superfluous. 1952B. Russell (title) The impact of science upon society. 1958Church Times 8 Aug. 7/1 The story..is presented by means of narrative and dramatic episodes in a manner familiar to all radio-listeners, but it is the lighting which makes the great impact. 1965Listener 26 Aug. 297/1 However much you give them, you are not going to make a significant impact on growth, though you may make an impact in the charitable sense. 1966Economist 10 Dec. 1144/3 What has had an impact on food distributors, apparently, is the opening of an investigation by the Federal Trade Commission into supermarket games and stamps. 1967E. Short Embroidery & Fabric Collage i. 18 The most dynamic colour combination if used too often loses its impact. 1969Ld. Mountbatten in Times (India Suppl.) 13 Oct. p. i/1 He [sc. Gandhi] made such an impact on me that his memory will forever remain fresh in my mind. 1973Daily Tel. 5 Mar. 6/2 The main impact of the campaign will be made by full-page newspaper advertisements.
2. Special Comb.: impact crater, a crater or a hollow in the ground believed to have been produced by the impact of a meteorite; impact extrusion, a process for producing tubular objects in which metal in a die is struck by a punch that fits into it and forces the metal between their two surfaces and out of the die; impact head = impact pressure; impact load, a load imposed suddenly and for a short time, as when one body strikes another; impact loading, (the application of) an impact load; impact pressure, the total pressure in a moving fluid in the direction of flow, being equal (in the case of a fluid of negligible viscosity) to the sum of the dynamic pressure and the static pressure; impact printer, a printer that depends on mechanical pressure to transfer ink from a ribbon to the paper; so impact printing; impact resistance = impact strength; impact strength, the ability of a solid to withstand an impact or shock; strength as measured by an impact test; impact test, any of various tests for measuring the resistance of a body to suddenly applied stress in which it is broken, usually by a blow, under standard conditions; impact tube, a thin tube (usu. rigid with a right-angled bend) which may be placed in a flow of fluid with an open end facing upstream, so that the impact pressure in the fluid may be found by measuring the pressure in the tube; cf. Pitot tube.
1895G. K. Gilbert in Bull. Philos. Soc. Washington XII. 265 The inquiry has followed three lines. First, an investigation of the ellipticity of lunar craters; second, an experimental investigation of the relation between incidence angle and ellipticity of impact craters; third, a more refined investigation of the orbital relations affecting the incidence angles of moonlets. Ibid. 291 Does the earth exhibit impact craters? If not, then erosion and sedimentation have destroyed them. 1965R. B. Baldwin Fund. Survey Moon vii. 66 If it can be shown that the impact craters on earth are..similar to lunar craters..we will be on firm ground in considering that the lunar craters..were formed by the impacts..of meteorites. 1967Listener 20 Apr. 521/2 Another impact crater is that at Wolf Creek in Australia, where the diameter is half a mile.
1935Metal Industry 11 Oct. 373/1 A new..heavy duty press..for the cold impact extrusion of aluminium tubes and shells in one operation. 1963H. R. Clauser Encycl. Engin. Materials 340/1 Parts produced by impact extrusion are essentially longitudinally oriented, e.g., collapsible tubes, cans, etc.
1928G. Martin Treat. Chem. Engin. xvi. 3 A connection between the density of a fluid W and the power required to move it through a pipe of area A when the impact head is l1 in. of water and the dynamic head is l in. of water.
1924E. E. Mann Introd. Pract. Civil Engin. x. 166 Wind pressure on roofs is of the nature of an impact load. 1928C. F. S. Gamble Story N. Sea Air Station 10 Her two stream-lined gondolas..were designed to be capable of sustaining severe impact loads when alighting on water. 1963D. A. Firmage Fund. Theory of Struct. iii. 56 Impact load is only a minor portion of the total load on any bridge.
1948Courant & Friedrichs Supersonic Flow & Shock Waves iii. 240 The basic problem of wave propagation in a bar of elastic-plastic material is concerned with the motion resulting from impact-loading, i.e., from a velocity being suddenly imparted to one end of the bar and then maintained there. 1973Sci. Amer. Feb. 85/1 It has been equipped with a grille structure that distributes the impact loading more uniformly.
1919A. B. Eason Flow & Measurem. Air & Gases xiv. 237 The increase in the value of the impact pressure in the case of wind blowing directly on an opening will be due to the fact that more of the momentum of the air is destroyed than when air blows on the small area of the Pitot tube mouthpiece. 1966Daily & Harleman Fluid Dynamics vi. 128 For liquids of small viscosity, Eq. (6–71) can be used to compute the velocity from the stagnation or impact pressure measured on the blunt nose of a probe in a steady flow.
1966IEEE Trans. Electronic Computers XV. 794/1 The output includes an electromechanical actuator which propels a small hammer against a single or multipart paper pack and ribbon which together strike a moving font of type at the precise moment the type character desired to be printed is in collision position. Thus, this type of printing uses an ‘on-the-fly’ principle; it is called impact printing. 1970Computer & Humanities V. 21 The board of directors..has approved a character set to be used on computer-driven impact printers handling machine-readable bibliographic information. 1985Personal Computer World Feb. 111/1 (Advt.), Being an impact printer, the M-loog will print on virtually any paper.
1934B. Stoughton Metall. Iron & Steel (ed. 4) xiii. 404 Impact Resistance of Steel.—The resistance of steel to shock decreases very much with lowered temperature. 1958C. L. Mantell Engin. Materials Handbk. iii. 12 The impact resistance of standard malleable iron, measured by the Charpy test using a notch, 0·394-in. square bar, and 0·079-in. depth of notch is about 16·5 ft-lb.
1904Proc. Inst. Mech. Engin. iv. 1227 The more or less consistent relation that appeared to exist in Messrs. Sankey and Kent-Smith's tests between impact strength and reduction of area. 1939Proc. Amer. Soc. Testing Materials XXXVIII. ii. 39 There are..8,000,000 molded phenol plastic telephones in use... The extent to which..breakage occurs..is determined largely by the impact strength of the molding material. 1952Wood & Von Ludwig Investment Castings for Engineers x. 209 Both beryllium copper and aluminum bronze will develop higher tensile strength and hardness when heat treated, but they will not have good impact strength, whereas manganese bronze is one of the toughest cast metals available. 1967M. Chandler Ceramics in Mod. World iv. 118 The impact strength of all ceramic materials..is rather low.
1899W. C. Unwin Testing Materials of Construction (ed. 2) 239 (heading) Example of an impact test. 1915[see Charpy]. 1918Machinery 31 Jan. 477/1 Tensile impact tests, in which a sudden tensile stress is applied to a specimen by means of a falling weight, have also been practised..in recent years. 1943F. D. Jones Engin. Encycl. (ed. 2) II. 680 The torsion impact test breaks the specimen by twisting. 1971B. Scharf Engin. & its Lang. iv. 24 The most common impact test in this country [sc. Great Britain] is the Izod test, in which a notched test piece fixed at one end is broken by a blow from a pendulum hammer, the energy absorbed in fracturing the specimen being recorded... Another method widely used in other countries and increasingly also in this country is the Charpy impact test, in which a notched test piece supported at both ends is broken by a blow from a striker, on the face opposite to and immediately behind the notch, the energy absorbed in fracturing the specimen being recorded.
1916Trans. Amer. Soc. Mech. Engin. XXXVII. 1410 For high pressures, the manometer attached to the impact tube can be replaced by a mercury column or steam gage attached to a receiver in the main where velocity is largely reduced. 1934J. H. Perry Chem. Engineers' Handbk. 689 The length and shape of the tip, so long as the opening faces upstream, usually have little effect upon the head indicated by an impact tube. 1966Daily & Harleman Fluid Dynamics ix. 178 The actual readings from impact tubes will depend both on the viscous effect and on the size of the pressure-sensing hole in the probe tip.
▪ II. † imˈpact, ppl. a. Obs.
[ad. L. impact-us, pa. pple. of impingĕre to impinge.]
= impacted (of which, in later use, it was prob. taken as a shortened form). Const. as pple. or adj.
1563T. Gale Antidot. i. iv. 3 When..there are humours impacte in anye part. 1587M. Grove Pelops & Hippod. (1878) 81 From hir whose picture still I fynde within my brest impact. 1647H. More Song of Soul iii. 1. ix, All these forms..That sense or phansie ever had impact. 1652French Yorksh. Spa iv. 43 A cold, crass slimy morbifick, or a hot impact matter.
▪ III. impact, v.|ɪmˈpækt|
[orig., and usually, in pa. pple. impacted, which was prob. directly f. L. impact-us + -ed1 (see impact ppl. a. and impacted); the verb proper being a later back-formation from this. See -ed1 2, and cf. compact v.1]
1. trans. To press closely into or in something; to fix firmly in; to pack in.
1601Holland Pliny xx. xxi. II. 73 The seed of this hearbe remooveth the tough humours bedded in the stomacke, how hard impacted soever they be. 1709Blair in Phil. Trans. XXVII. 75 These Pyramids, which receive the Hairs, are impacted in the Cutis. a1791Wesley Serm. lxxxii. i. 5 Wks. 1811 IX. 417 Impact fire into iron, by hammering it when red hot. 1897Allbutt Syst. Med. III. 835 A stone-like mass..which had become impacted in the lower ilium.
2. To stamp or impress (on something). rare.
1677Gale Crt. Gentiles iv. Proem 4 Ideas or notions impacted on the mind. Ibid. 442 Every..Creature has a law impacted or impressed on its Being.
3. intr.
a. To come forcibly into contact with a (larger) body or surface. Const. various preps.
1916[see impacting ppl. a. below]. 1929‘Seamark’ Down River vi. 172 Something impacted with a soft thud against Lingard's temple. 1945Jrnl. Sci. Instrum. XXII. 191 A jet of air issuing from a slot and impacting on a plane surface. 1962F. I. Ordway et al. Basic Astronautics v. 201 The Soviet Lunnaya Raketa was launched early in the afternoon of September 12, 1959 and impacted onto the Moon's surface just after midnight on September 14, Moscow time.
b. fig. To have a (pronounced) effect on.
1935W. G. Hardy Father Abraham 370 For there was about them an air of eagerness and of shuddering expectation which impacted on his consciousness and fascinated even while it repelled him. 1956Oxf. Mag. 8 Nov. 81/1 The Magazine.. is not the place for consideration of national and international events except in so far as they impact on Oxford.
4. trans. To cause to impinge or impact on, against, etc.
1945Jrnl. Sci. Instrum. XXII. 187 Experimental results for the efficiency of jets in impacting particles are correlated. 1964K. Stewart in White & Smith High-Efficiency Air Filtration ii. 57 All impactors make use of the inertia effect which particles exhibit when the gas stream in which they are suspended is constrained to turn abruptly. The particle under suitable conditions cannot follow the stream lines and is impacted against a collecting plate. 1972J. O. Ledbetter Air Pollution A. v. 187 An aerosol moving toward an obstacle may impact particles on the obstacle.
Hence impacting ppl. a., impinging, colliding.
1916‘Boyd Cable’ Action Front 95 No ping and smack of impacting lead hailed about them. 1961Sci. Amer. Nov. 58/2 The impacting bodies may have been asteroids or comets. 1972Daily Tel. 17 Apr. 6/8 These particles..cannot be measured or analysed from the Earth's surface. On the Moon, however, the impacting particles leave trails in the detector. 1973Nature 13 July 68/2 Craters of the size of St Magnus Bay and The Firth would be formed by impacting meteorites of masses about 1 million tons. |