| 释义 |
▪ I. impulse, n.|ˈɪmpʌls|
[ad. L. impuls-us a push against, f. ppl. stem of impellĕre to impel.]
1. a. An act of impelling; an application of sudden force causing motion; a thrust, a push.
1650Ashmole Chym. Collect. (ed. 3) 227 The Second lurketh in the bowels of the Earth, by the Impulse and action, whereof the Subterraneous vapours are driven upwards through Pores and Pipes. 1690Locke Hum. Und. iv. x. §19 We cannot conceive how any thing but impulse of body can move body. 1752Hume Ess. & Treat. (1777) II. 68 The impulse of one billiard-ball is attended with motion in the second. 1758Johnson Idler No. 2 ⁋1 He will wish to advance rather by the impulse of the wind, than the strokes of the oar. 1860Tyndall Glac. ii. i. 228 To produce the impression of violet light a still greater number of impulses is necessary. 1872Huxley Physiol. viii. 210 The chief agents in transmitting the impulses of the aërial waves. 1875Darwin Insectiv. Pl. x. 240 When a gland is first excited the motor impulse is discharged within a few seconds.
fig.1692Bentley Boyle Lect. i. 12 Driven on by the blind impulses of Fatality and Fortune. 1818Jas. Mill Brit. India II. v. ix. 698 The total exemption of the deliberations in parliament from the impulse of the royal will. 1877Mrs. Oliphant Makers Flor. vi. 160 The early impulse of the Renaissance [was] just then beginning to influence the world.
b. Path. ‘The shock felt on the chest-wall when the heart beats, or over an aneurysm during the cardiac systole..Cardiac impulse, the apex beat of the heart’ (Syd. Soc. Lex. 1886).
1879St. George's Hosp. Rep. IX. 182 Of the Heart: No sensible impulse; sounds hardly audible. Ibid., Area ill-defined; impulse diffused; sounds muffled.
2. Dynamics.
a. An indefinitely large force enduring for an inappreciably short time but producing a finite momentum; such as the blow of a hammer, the drive of a bat, the impact of colliding balls, etc.
b. The product of the average value of any force multiplied by the time during which it acts. (This extended use was introduced by Clerk Maxwell Matter & Motion 43.)
1796Hutton Math. Dict., Impulse, the single or momentary action or force by which a body is impelled. 1806― Course Math. II. 132 The Momentum, or Quantity of Motion, generated by a Single Impulse, or any Momentary Force, is as the Generating Force. 1859Lunn Of Motion 87. 1868 E. J. Routh Rigid Dynamics (ed. 2) 262 We may regard an impulse as the limit of a large finite force acting for a very short time. 1875Maxwell Theory of Heat (ed. 4) 88 The impulse of a force is equal to the momentum produced by it. 1868W. K. Clifford Lect. (1879) I. 76 A shuttlecock, which has its entire state of motion suddenly changed by the impulse of the battledore.
c. Aeronaut. specific impulse: the ratio of the thrust produced in a rocket engine to the rate of consumption of propellant (expressed as mass, or weight, per second).
Equivalent to the impulse (sense 2 b) obtained per unit mass, or weight, of propellant.
1947Jrnl. Brit. Interplanetary Soc. Mar. 101 The most important requirement is a low consumption, or to use a term more commonly employed in rocketry, a high ‘specific impulse’; the specific impulse being the thrust obtained from the consumption of one unit of propellant mixture per second. 1950Sci. News XV. 76 The most useful measure of the efficiency of a rocket is called ‘specific impulse’. 1962F. I. Ordway et al. Basic Astronautics x. 422 In the liquid fuel reactor hydrogen is bubbled through liquid uranium compounds. With this method specific impulses on the order of 1500 lb-sec/lb may be attained. 1971P. J. McMahon Aircraft Propulsion iii. 116 In the foot-pound-second system, specific impulse has the units lbf-sec/lb. For many years it was the practice to define the specific impulse as the thrust divided by the weight flow rate of propellants. Using this definition the units of specific impulse became ‘seconds’. Ibid. x. 298 The specific impulse of a cordite type propellant will be of the order of 2 000 N-s/kg when operating with a chamber pressure of 6 000 kN/m2 and exhausting to 100 kN/m2.
3. a. Force or influence exerted upon the mind by some external stimulus; suggestion, incitement, instigation. † Formerly, esp., A strong suggestion supposed to come from a good or evil spirit.
1660R. Coke Power & Subj. 177 If he by chance offend by the impulse of the Devil, let him make amends therefore. 1674Owen Holy Spirit (1693) 184 An immediate Revelation or Divine Impulse and Impression. 1701G. Hammond (title) Discourse of Angels..also something touching Devils, Apparitions, and Impulses. 1798Wordsw. Tables turned vi, One impulse from a vernal wood May teach you more..Than all the sages can. 1833Cruse Eusebius ii. i. 49 Thomas, under divine impulse, sent Thaddeus as herald and evangelist. 1847Prescott Peru (1850) II. 138 He was not a man..to yield timidly to the impulses of others.
b. Incitement or stimulus to action arising from some state of mind or feeling.
1647Clarendon Hist. Reb. i. §60 His purpose..proceeded only from himself and the impulse of his own Conscience. 1769Robertson Chas. V (1813) III. xi. 281 No motive to direct him but the impulse of ungovernable passions. 1833H. Martineau Charmed Sea i. 2 Some ran on, under an impulse of curiosity. 1853J. H. Newman Hist. Sk. (1876) II. i. iii. 107 The inward impulse of gigantic energy and brutal cupidity urged them forward.
c. Sudden or involuntary inclination or tendency to act, without premeditation or reflection.
1763Burke Corr. (1844) I. 50, I act almost always from my present impulse, and with little scheme or design. 1861Geo. Eliot Silas M. ii. 12 He seemed to weave, like the spider, from pure impulse, without reflection. 1869Freeman Norm. Conq. III. xiii. 281 Men..are apt to be guided by impulse rather than by judgement. 1876T. Hardy Ethelberta (1890) 271 It was mere impulse.
4. a. The effect produced by impulsion; motion caused by the sudden application of force; momentum, impetus.
1715Desaguliers Fires Impr. 8 A Ray..goes on by a compound Motion made up of its Impulse..and its constant tendency upwards. a1721J. Keill Maupertuis' Diss. (1734) 25 The motion of such a Vortex..ought to give them some horizontal Impulse, and hurry them along in its own direction. 1856Kane Arct. Expl. I. xii. 133 My team..leaping them..and the impulse of our sledge carrying it across. 1878Huxley Physiogr. 188 The impulse may be transmitted through the earth to an enormous distance.
fig.1872Yeats Growth Comm. 97 Orseolo gave a new impulse to navigation. 1874Green Short Hist. vii. §7. 418 Circumstances..were giving a poetic impulse to the newly-aroused intelligence of men.
b. Path. ‘The wave of change which travels through nerve and muscle in passing from rest into action’ (Syd. Soc. Lex. 1886).
c. Dancing. (See quot. 1949.)
1949Shurr & Yocom Mod. Dance 190 Impulse, the impetus or impelling force used to initiate a movement sequence, such as a hip contraction or a hip release. 1968J. Winearls Mod. Dance (ed. 2) ii. 64 Thus with continued forward impulses the pelvis moves in a backwards—downwards—forwards—upwards—circle with an accent at the bottom of the circle.
5. Electr. A sudden, momentary change in voltage or current from an otherwise steady (or slowly varying) value. (More commonly pulse.)
1883E. Atkinson tr. Ganot's Elem. Treat. Physics (ed. 11) x. vi. 850 As they are all connected together we get, not so much a series of separate impulses, as a continuous series of currents. 1904Daily Chron. 10 Dec. 7/2 It [sc. a tape] is inserted in the aperture of the transmitting instrument, and by the perforations the electrical impulses are created and recorded at the receiving station. 1943A. L. Albert Fund. Telephony ix. 206 The vertical movement of the selector switch is controlled by the electric impulses received from the subscriber's dial. 1971H. E. Ennes Television Broadcasting vii. 347 The circuit works by virtue of the fact that spurious noise impulses normally are much narrower than the desired sync pulses.
6. attrib. and Comb., esp. in various technical terms relating to the driving mechanism of a clock, as impulse-teeth, etc.
1825J. Nicholson Operat. Mechanic 520 The impulse-teeth consist of very small tempered steel pins, inserted on the surface of the rim of the wheel on one side only. 1879Cassell's Techn. Educ. IV. 369/2 The impulse-arc of the balance..is determined by the radii of lever and roller. 1884F. J. Britten Watch & Clockm. 55 The escape wheel..overtakes the impulse pallet and drives it on. Ibid., The impulse roller. Ibid. 97 The impulse teeth..the impulse finger. 1901Daily Chron. 3 Sept. 3/7 A genuine chivalrous impulse-desire—that natural desire for companionship. 1929D. H. Lawrence Let. 1 Oct. (1962) II. 1204 You are working all the time from wrong impulse-sources. 1949M. Mead Male & Female xvii. 355 Modern psychology and modern literature emphasize the importance of impulse gratification.
b. Special Comb.: impulse clock, dial, a secondary clock operated by electrical impulses transmitted at regular intervals by a master clock; impulse coupling = impulse starter; impulse-reaction turbine, a turbine comprising two (or more) stages, one working on the principle of the impulse turbine and the other on that of the reaction turbine; impulse starter, a mechanical device which may be fitted to the magneto of an ignition system to cause its rotor to turn in a series of jerks instead of continuously, resulting in an increased voltage that facilitates the production of a spark at low speeds or when starting; impulse tube, a tube serving to expel a torpedo; impulse turbine, a turbine in which the working fluid undergoes no drop in pressure in the rotor, this being driven solely by the change it causes in the direction of flow; impulse-wheel, a form of turbine water-wheel driven by the impact of a jet upon it (Cent. Dict.).
1923Langman & Ball Electr. Horology v. 82 Clocks coming under this section are generally..designated as dials, impulse clocks, secondary clocks, journeyman clocks, sympathetic clocks, or step by step movements. 1951S. J. Wise Electr. Clocks (ed. 2) iv. 67 An impulse or repeater clock is a device which receives the timed electrical impulses transmitted by a master clock, and translates them, through its wheelwork, into seconds, minutes and hours.
1916Impulse coupling [see impulse starter below]. 1943A. P. Fraas Aircraft Power Plants viii. 147 To ensure a good spark at cranking speeds the magnetos for many of the smaller engines are fitted with an impulse coupling.
1931F. Hope-Jones Electr. Clocks ii. 6 Circuits of electrical impulse dials, in which a master clock transmits impulses every minute or half-minute to propel the hands. 1940― Electr. Timekeeping i. 6 After many years of futile attempts to apply electricity to horology, inventors turned their attention to systems of electrical impulse dials, an obviously sane and effective method of indicating uniform time throughout a large building.
1929T. M. Naylor Steam Turbines i. 4 Combination turbines or disc and drum turbines, as they are often called, are a combination of impulse and reaction types of turbine. The first part of the turbine is impulse, and the remainder of the turbine is reaction, so that this type of turbine might be called impulse-reaction. 1951Engineering 5 Oct. 438/3 The high-pressure turbine is of the impulse-reaction type.
1916V. W. Pagé Automobile Starting iii. 224 The device..is known as the Eisemann impulse starter coupling. This may be attached to any model of Eisemann magneto and is said to have no effect upon its regular operation except at slow speeds, when it causes the armature to rotate in a series of jumps instead of at a uniform speed. 1940W. E. Crook Electr. in Aircraft vii. 93 The impulse starter..enables the engine to start on its own magnetos. It is a purely mechanical piece of apparatus, consisting essentially of a spring-loaded pawl and ratchet gear.
1877Illustr. London News 14 Apr. 339/3 It is fired by what is called an ‘impulse-tube’, which..discharges the torpedo into the water. 1878Cassell's Family Mag. 312/2 Direction is given to the torpedo by means of an iron impulse-tube built into the vessel. 1885Marine Engineer 1 Sept. 144/2 The fish torpedoes lie side by side. Immediately behind them..are a couple of ‘impulse tubes’.
1881Encycl. Brit. XII. 524/1 In some turbines the whole available energy of the water is converted into kinetic energy before the water acts on the moving part of the turbine. Such turbines are termed Impulse Turbines, and they are distinguished by this that the wheel passages are never entirely filled by the water. 1906W. H. S. Garnett Turbines iv. 42 Impulse turbines..are unsuited for the development of high speed motion from low falls... For running, on the other hand, at low speeds under a high fall, the impulse turbine cannot be surpassed. 1971P. J. McMahon Aircraft Propulsion v. 163 The extreme case of a zero reaction stage wherein all the pressure drop occurs in the nozzle blades is known as an ‘impulse turbine’ in accordance with steam turbine practice. A pure impulse turbine would rarely be used for an aero⁓turbine engine.
c. Of or pertaining to a purchase or purchases made on impulse, usu. at the point of sale of displayed goods, as impulse buyer, impulse buying, etc.
1959Times Lit. Suppl. 29 May (Children's Books) 5 [Children's books] snarl ‘impulse buyers’ in the supermarket. 1959Sunday Express 26 July 10/4 The Opposition Leader's Lady and Judy O'Grady are ‘impulse buyers’ under the skin. 1959News Chron. 18 Nov. 4/2 What the traders call ‘impulse buying’ is increasingly popular. 1962Sunday Express 8 July 15/2 Top dressers..plunge with the odd ‘impulse buy’. 1963Punch 27 Nov. 772 New Prime Minister..impulse-buys sixty Phantom 11s. 1964Punch 6 May 655/3 Trolleys full of impulse-bought bargains. 1965Mod. Law Rev. XXVIII. v. 557 None of the reasons given for minimising the importance of ‘impulse sales’ apply with special force to the book trade. 1967L. J. Braun Cat who ate Danish Modern x. 88 These are little boutique items for the impulse buyer. 1968‘S. Jay’ Sleepers can Kill vi. 66 He goes into a shop..and buys a boat... An impulse buy, if ever there was one. 1972New Statesman 26 May 709/3, I impulse-bought some crumpets the other day, because they were on the counter at the dairy.
▪ II. imˈpulse, v.
[f. the n. or f. L. impuls-, ppl. stem of impellĕre to impel; cf. obs. F. impulser.]
trans. To give an impulse to; to impel; to instigate. Also intr.
1611Florio, Impulsare, to impulse, to perswade often. 1614Raleigh Hist. World i. (1634) 34 With that force so impulsed and prest they are carried under the deepe Ocean. 1658Bromhall Treat. Specters i. 102 The Man being impulsed by some invisible spirit. 1689T. Plunket Char. Gd. Commander 45 The Earth's fill'd with fraud and violence, Impulsed by the Jesuits influence. a1711Ken Hymns Festiv. Poet. Wks. 1721 I. 307 Love to the Cross his Soul impuls'd. a1718Penn Tracts Wks. 1726 I. 548 His Good Angel or Spirit..very often impuls'd or moved him to preach to the People. 1757E. Griffith Lett. Henry & Frances (1767) II. 55 The Centrifugal [power]..is a force impulsed upon all the planets, at their creation, that directs them forward, in a right line. 1931Times 27 June 11/5 The interference is due..to..sparks in stays of masts, and to loose metallic contacts, which impulse the receiver in the same way as heavy atmospherics would do. 1936Nature 12 Sept. 445/2 The law and governmental forms..clearly lag behind even economic developments as impulsed by scientific discovery. 1943Gloss. Terms Telecomm. (B.S.I.) 62 Impulsing signal, a signal carrying the selective information to steer the call in the desired direction. 1949E. C. Berkeley Giant Brains iii. 41 This type of relay has the property of staying..in either position until the opposite coil is impulsed. 1960Lang. & Speech III. 140 (title) Recurrently impulsed resonators in speech and psycho⁓physical studies. 1972J. Quartermain Rock of Diamond xiii. 72 Her small voice..impulsed through the network of cables.
Hence imˈpulsing vbl. n.
1885L. Oliphant Sympneumata xiii. 207 They may trace..the radiant current through the human story of the Divine impulsings. |