Упр. 12. Переведите цепочки однокоренных слов

1. associate – association – associated – associative

2. vary - variable – variety – variant – various

3. compete –competition – competitor – competitive – compatibility

4. simulate – simulated – simulator – simulation

5. convert – converter – conversion – convertible – convertibility

6. emit – emitted – emission –emissive

7. sense – senseless – sensibility – sensible – sensitive – sensor

Упр. 13. Прочитайте и переведите текст. Обратите внимание на перевод атрибутивных сочетаний (N+N), в которых главным является последнее слово.

Poppet valves are used almost exclusively in internal combustion reciprocation engines because of the demands for tightness with high operating temperatures and pressures. The valves are generally 2 inches in diameter or smaller on high-speed automotive-type engines. They are cam-operated and spring-loaded. They are cooled by transferring heat to the engine jacket, mostly through the valve stem. Exhaust valves are subject to the effects of extreme temperature and must accordingly be most carefully designed and constructed of alloy metals.

By valve train, we mean the valves and valve-operating mechanism by which an internal combustion engine takes air or a fuel-air mixture into the cylinders and discharges the combustion products to the exhaust. Mechanically, an internal combustion engine is a reciprocating pump, able to draw in a certain amount of air per minute. Since the fuel takes up little space but needs air with which to combine, the power output of an engine is limited by its air-pumping capacity.

It is essential that the flow through the engine can be restricted as little as possible. This is the first requirement for valves. The second is that they close off the cylinder during the compression and power strokes.

In most 4-stroke engines, the valves are of the inward-opening poppet type, with the valve head ground to fit a conical seat in the cylinder block or cylinder head.

The valve head is held concentric with its seat by a cylindrical stem running in the valve guide. The valve is held closed by a compressed helical spring. The valve is opened wide by lifting it from its seat a distance equal to approximately 25% of the valve diameter. Valves are usually made of a stainless, non-scaling alloy which will keep its strengthened shape at high temperature. Exhaust valves sometimes are made hollow and partially covered with metallic sodium to permit more effective cooling.

Engine valves are usually opened by means of cams.

A follower or valve-lifter is riding on each cam. It may be a flat or slightly convex surface, or a roller. The valve is opened by forces applied to the end of the valve stem through a mechanical linkage activated by the cam follower. The camshaft placed in the crankcase is usual in standard automobiles. The operating linkage consists of cam follower, push rod and rocker arm. The push rod is a light rod or tube with ball ends which carries the motion of the cam follower to the rocker arm. The rocker arm is a lever, pivoted near its centre so that as the push rod raises one end, the other end depresses the valve stem, opening the valve.