| 释义 |
▪ I. ‖ lumen|ˈl(j)uːmɛn|
Pl. lumina |ˈl(j)uːmɪnə|.
[L. = light; an opening.]
1. An opening, passage, or canal.
a. Anat. and Zool.
b. Bot.
c. Surg. The passage of any tube in an instrument.
a.1873T. H. Green Introd. Pathol. (ed. 2) 81 The vessel thus calcified, loses its..contractility; its lumen is diminished. 1888Beddard in Encycl. Brit. XXIV. 680/2 A longitudinal fold on the dorsal side which projects into the lumen of the intestine. 1893Shipley Zool. Invertebr. 214 In the lumen of the siphon is a small valve.
b.1887Garnsey & Balfour tr. De Bary's Fungi 321 The hyphæ..usually have their walls thickened till the lumina disappear. 1900Jackson Gloss. Bot. Terms, Lumen, the space which is bounded by the walls of an organ, as the central cavity of a cell.
c.1889Lancet 9 Nov. 949/1 Tracheotomy was resorted to, the larger lumen of the tube affording a freer vent. 1894Ibid. 3 Nov. 1033 The lumen of the catheter.
2. [First adopted, in Fr., by A. Blondel 1894, in La Lumière électrique 7 July 10.] A unit of luminous flux (now incorporated into the International System of Units), equal to the flux emitted by a point source of intensity one candela (formerly, one candle) into a solid angle of one steradian.
The total flux emitted by a source of one candela is 4π (= about 12·57) lumens.
1898Astrophysical Jrnl. VII. 300 Luminous current is defined as the rate at which luminous energy is emitted by a point-source through a solid angle of one steradian. Unit: The luminous current of one candle, i.e., of one Hefner lamp. Name: ‘Lumen’. Proposed by L. Weber. 1937Times 13 Apr. p. iv/2 Electric discharge lighting..has been recently installed to give an even and intense illumination of 1,120,000 lumens so that any flaw or defect in the panels being produced may be detected at once. 1953Amos & Birkinshaw Television Engin. I. vii. 125 The efficiency of electric lamps is usually expressed in lumens per watt... For gas-filled lamps the efficiency increases steadily with the rating and is approximately 10 lumens per watt for 25 W lamps, 13 lumens per watt for 100 W lamps and 17·5 lumens per watt for 1 kW lamps. Thus a 100 W lamp radiates a total of 1,300 lumens and is equivalent to a source of 1,300/4π, i.e., approximately 100 candle-power. 1974Which? Mar. 88/3 The long-life bulbs gave a light output of about 600 lumens after one hour of life.
3. Special Comb.: lumen-hour, the quantity of light corresponding to a flux of one lumen radiated for one hour; similarly lumen-second.
1925Trans. Illuminating Engin. Soc. (U.S.) XX. 630 The Lumen-hour is the unit of quantity of light. It is equal to a flux of one lumen continued for one hour. 1975Times 21 Mar. 20/3 The public wanted a certain package of candlepower (expressed in lumens); the industry assured certain fixed wattages, and then aimed at the minimum cost per lumen-hour for those wattages.
1930tr. L. P. Clerc's Photogr. ii. 7/2 The unit of exposure is the lumen-second or candle-metre-second. 1958Newnes Compl. Amat. Photogr. x. 110 The light output of a flash⁓bulb is measured in lumen seconds.
▪ II. lumen
obs. pl. of limb n.1 |