单词 | x-cut |
释义 | > as lemmasX-cut a. In Algebra and Higher Mathematics used as the symbol for an unknown or variable quantity (or for the first of such quantities, the others being denoted by y, z, etc.); spec. in Geometry, the sign for an abscissa, or quantity measured along the principal axis of co-ordinates (hence called the †axis of x; now always x-axis; also transferred). X-cut adj. (Electronics), of, pertaining to, or designating a quartz crystal cut in a plane normal to its X-axis; X-plate (Electronics), each of a pair of electrodes in an oscilloscope that control the horizontal movement of the spot across the screen. Hence allusively for something unknown or undetermined (also attributive and in combinations). See also X-ray n. and adj.The introduction of x, y, z as symbols of unknown quantities is due to Descartes ( Géométrie, 1637), who, in order to provide symbols of unknowns corresponding to the symbols a, b, c of knowns, took the last letter of the alphabet, z, for the first unknown and proceeded backwards to y and x for the second and third respectively. There is no evidence in support of the hypothesis that x is derived ultimately from the medieval transliteration xei of šay' ‘thing’, used by the Arabs to denote the unknown quantity, or from the compendium for Latin res ‘thing’ or radix ‘root’ (resembling a loosely-written x), used by medieval mathematicians. ΘΚΠ the world > relative properties > number > mathematical notation or symbol > [noun] > figure > for unknown or variable quantity X1660 N1690 the world > relative properties > number > geometry > geometric space > [noun] > division or marking of > axis > of coordinates > co-ordinate > in specific direction X1660 Z1660 Y1728 abscissa1756 ordinate1855 the world > relative properties > number > geometry > geometric space > [noun] > division or marking of > axis > of coordinates Y axis1875 axis of x1885 y-axis1885 x-axis1886 z-axis1929 the world > matter > physics > solid state physics > semiconductivity > [adjective] > designating type of crystal X-cut1930 the world > matter > physics > electromagnetic radiation > electronics > electronic devices or components > cathode-ray tube > [noun] > oscilloscope > electrode in X-plate1934 Y-plate1946 1660 J. Moore Arithm. ii. i. §19. 16 (Algebra) Note alwayes the given quantities or numbers with Consonants, and those which are sought with Vowels, or else the given quantities with the former letters in the Alphabet, and the sought with the last sort of letters, as z y x, &c. lest you make a confusion in your work. 1709 J. Ward Young Mathematician's Guide (1713) iv. iii. 380 Let y = As the Abscissa, and z = SP, put x = Aa the Distance between the two Semi-ordinates; which we suppose to be infinitely near each other. 1726 E. Stone New Math. Dict. at Conoid If a be equal to the Transverse Axis of the Hyperbola, generating a Conoid, and x be the Heighth of the Conoid, or the Absciss of the Hyperbola. 1771 Encycl. Brit. II. 269 The equation of any curve, is an algebraic expression, which denotes the relation betwixt the ordinate and abscissa; the abscissa being equal to x, and the ordinate equal to y. 1839 Penny Cycl. XIII. 175/2 [article Kant] What is that unknown principle (= X) on which the understanding relies, when of the subject A it finds a foreign predicate B, and believes itself justified in asserting their necessary connexion? 1885 J. Casey Treat. Analyt. Geom. ii. 22 If the equation of the line contains no x, it is parallel to the axis of x; and if it contains no y, it is parallel to the axis of y. 1886 W. B. Smith Elem. Co-ordinate Geom. i. i. 10 OX, OY, are called Co-ordinate Axes, or axes of X and Y, or X- and Y-axes. 1893 F. W. L. Adams New Egypt 29 The x of the Egyptian equation being pretty obviously the Egyptian people. 1898 W. T. Stead in Daily News 8 Nov. 5/4 What manner of man is its author? He is the X in the equation. 1898 A. Lang Making Relig. ii. 15 Research in the X-region is not a new thing under the sun. 1903 J. B. Greenough & G. L. Kittredge Words v. 53 To make fun of the x's and y's of the algebraist. 1906 Daily Chron. 12 May 4/3 There is ‘a wholesome distrust,’ says Professor Ewing, ‘of what may be called x-chasing.’ 1929 Internat. Crit. Tables (National Res. Council U.S.) VI. 211/1 The z-axis coincides with the crystallographic c-axis of 3-fold symmetry, the y-axis is ⊥ to a face of the hexagonal first order prism, and, in dextro crystals, the + direction of the x-axis is outward through one of the faces..of the trigonal pyramid. 1930 W. G. Cady in Proc. IRE 18 2139 We consider first the manner of indicating the orientation of the more common ‘cuts’ [in quartz crystals]... In the first case, we have the cut variously referred to in the literature as ‘Curie cut’..or ‘normal cut’... However, a still more concise term would be the ‘X-cut’, denoting a plate the normal to whose face, and hence for which the applied electric field, is parallel to an X-axis. Similarly, the term ‘Y-cut’ would apply to the second type of quartz plate, which has hitherto been referred to as the ‘30-deg. cut’ or ‘parallel cut’. 1933 J. H. Morecroft Electron Tubes xii. 337 The velocity of [compression] wave travel is different in the Y axis direction from that along the X axis. 1933 J. H. Morecroft Electron Tubes xii. 338 An X-cut plate has a negative temperature coefficient, i.e. the frequency of oscillation decreases as the temperature rises... The Y-cut plates have a positive coefficient. 1934 J. H. Reyner Television vii. 71 We then apply a suitable periodic voltage across the X plates which spreads the trace-out at right angles and produces a pattern on the screen. 1945 Electronic Engin. 17 723 These two equations define the components of the velocity of the spot along the X and Y axes. 1946 Electronic Engin. 18 23/1 A D.C. connexion must be made between the output of the time base and the X plates of the tube. 1969 Funk & Wagnalls Dict. Electronics 170/1 X-axis, in a quartz crystal, a reference axis chosen so as to connect two opposite vertices of its hexagonal cross section; one of the axes showing the greatest electrical activity. 1973 S. K. Stein Calculus & Analyt. Geom. ii. 26 Far to the right and to the left the graph gets closer and closer to the x axis without ever touching it. 1978 D. T. Rees Cathode Ray Oscilloscope 9 A voltage applied to the X-plates will deflect the beam sideways. 1982 IEEE Trans. Industr. Electronics 29 158/1 The rotated X-cut orientation has been found to be optimum from the viewpoint of its frequency versus temperature and pressure characteristics. 1983 V. M. Ristic Princ. Acoustic Devices vi. 180 The relationship between the natural axes a, b, c and the crystallographic axes X, Y, Z must be known in order to use the proper constants. These relationships, for each crystal system, have been adopted by convention. Various piezoelectric, elastic, and other constants of a particular crystal specimen are evaluated in terms of X, Y, Z axes. < as lemmas |
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