| 释义 |
mesa|ˈmeɪsə|
[Sp. mesa, lit. ‘table’:—L. mēnsa.]
1. A high table-land. Also attrib.
1775Romans Florida App. 57 This Table Land is called Mesa Maria. 1859Marcy Prairie Trav. 314 The road..ascends to a low mésa. 18..Reports on Pacific Railroad I. 84 (Bartlett) The mesa, or table-land character, is exhibited only along the line of river-valleys. 1882Rep. to Ho. Repr. Prec. Met. U.S. 636 The top sometimes several miles wide, mesa-like and comparatively level. 1948C. A. Cotton Landscape (ed. 2) x. 139 (caption) The Schlern mesa, of dolomite, South Tyrol. 1951Wodehouse Old Reliable v. 68 There he was..under the dressing-table, with his fanny sticking up like a mesa in the Mojave desert. 1963A. Lubbock Austral. Roundabout 73 The descent on the northern side of the plateau winds down, between table-top mesas and rugged bluffs. 1970R. J. Small Study of Landforms iii. 72 To the east of Lyme Regis..very broad valleys are separated in interfluves occasionally surmounted by butte-like hills..and mesa-like plateaus developed in the near horizontal Upper Liassic sandstones. 1974H. MacInnes Climb to Lost World x. 163 Only the proud tops of the neighbouring mesas stood out above the swirling clouds. Ibid. xii. 217 We saw a magnificent panorama of mesas: a weird contorted skyline of grotesque sandstone figures towards the Venezuelan part of the summit.
fig.1963V. Nabokov Gift iii. 150 Out of the total of five hundred copies printed, four hundred and twenty-nine still lay, dusty and uncut, forming a neat mesa in the distributor's warehouse.
2. Electronics. In some transistors and semiconductor diodes, a raised, flat-topped portion of n- or p-type semiconductor surrounded by an area from which the upper layer has been etched away to expose the underlying p- or n-type material (respectively). Usu. attrib., as mesa diode, mesa transistor.
1958C. H. Knowles in Electronic Industries (Philadelphia) Aug. 55 Recent developments at several locations have resulted in a new line of VHF-UHF Transistors... We will refer to this new line of transistors as Mesa Transistors. Ibid., The Mesa Transistor gets its name from its physical configuration... A basic part of its structure is the ‘Mesa’, (Spanish name for ‘table’), which is the active region of the transistor. 1962Simpson & Richards Physical Princ. Junction Transistors viii. 169 Following construction of the device the germanium surrounding the electrodes was etched away to form the table-like area or ‘mesa’. 1966McGraw-Hill Encycl. Sci. & Technol. VII. 316/1 Silicon mesa diodes are also used for high-speed, low-power applications. 1972Boylestad & Nashelsky Electronic Devices & Circuit Theory iii. 137 The diffusion technique is employed in the production of mesa and planar transistors, each of which can be of the diffused or epitaxial type. 1973Nature 12 Jan. 92/3 Improved cut-off frequency..and noise performance result in useful performance up to 4 GHz with promise of extending this to at least 8 GHz by reverting to an improved version of the old ‘mesa’ design. |