時間：2011-03-11 23:13來源：藍天飛行翻譯 作者：admin 點擊：次
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dovetailing (woodworking). A method of joining pieces of wood to form the sides of a box or drawer. The ends of one piece of wood are cut with triangular-shaped cutouts that look like the spread-out tail of a dove. These cutouts are called the mortises. The other piece of wood is cut with tenons that are shaped so they exactly fit into the mortises. When the tenons are fitted into the mortises, they form a solid joint. dowel. A round wooden peg used to fasten pieces of wood together without the use of metal fasteners. Holes are drilled into each of the pieces to be joined, and a short dowel is pressed into the holes to hold the pieces together. dowel rod. A round piece of wood used to make dowels for holding pieces of wood together. Dow metal. The registered trade name for a series of magnesium alloys produced by the Dow Chemical Corporation. downburst (meteorology). A strong downdraft which induces an outburst of damaging winds on or near the ground. The sizes of downbursts vary from one-half mile or less to more than 10 miles. An intense downburst often causes widespread damage. Damaging winds, lasting from five to 30 minutes, could reach speeds as high as 120 knots. downdraft (meteorology). A relatively small-scale downward current of air. Downdrafts are often observed on the lee side of large objects that restrict the smooth flow of the air or in precipitation areas in or near cumuliform clouds. downdraft carburetor. A carburetor that mounts on the top of a reciprocating engine. Air entering the engine flows downward through the carburetor. downlocks (aircraft landing gear component). Mechanical locks used to hold a retractable landing gear in its down position. Downlocks prevent the landing gear from accidentally retracting when there is no hydraulic pressure on the actuating cylinder. downtime (aircraft operation). Any time during which an aircraft is out of commission and not able to be operated. downwash (aerodynamics). Air forced down by aerodynamic action below and behind the wing of an airplane or rotor of a helicopter. Aerodynamic lift is produced when air is deflected downward. The upward force on the aircraft is the same as the downward force on the air. When the mass of air in the downwash is equal to the weight of the aircraft forcing it down, the aircraft rises. downwash angle (aerodynamics). The angle formed between the direction of air movement as it approaches an airfoil and its direction as it leaves. An airfoil produces lift by deflecting air downward. The upward component of lift is equal to the downward component created by the mass of the down-washed air. downwind. The direction measured relative to the way the wind is blowing. Downwind means the direction in which the wind is moving. |
