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IV. Translate the sentences paying attention to the polysemy of the words in bold type.

1. We don't know the number (……………………..) of computer users in this country.

2. What is your telephone number (……………………..)?

3. As a rule programmers know a number of (……………………..)languages of programming.

4. A new processor was the “Number (……………………..)One” of presentation.

5. The latest achievements in cybernetics were published in October number (……………………..)of a scientific journal.

6. To satisfy the increasing demands of users a new high-speed computer was designed (…………………………………..……..) not long ago.

7. A new school was designed (…………………………………..……..)by a famous architect.

8. The icebreaker was designed (……………………….……………..……..)for operation in Arctic waters.

9. It was designed (……………………..…….……..……..)to fulfill the task till the end of month.

10. This result was not designed (……………………………………………..…..……..).

Text 7 metal joints

These joints are permanent. In soldering and welding heat used to achieve the joints. Rivets can also be used with sheet metal to effect a permanent joint. The decision on which method to use for metal jointing depends on the metal, the stress to which the joint will be subjected and the structure of work.

S oft solder. This is an alloy of tin and lead. It melts at +I85°C. As a jointing method it is easy and quick, particularly for brass, copper and metal sheet. The proportions of tin and lead in the solder should be varied with the task and metals involved. For example, if jointing sheet metal more lead needs to be used. This is because it melts at a higher temperature and so sets much harder. Conversely, if using solder for electronics more tin is required in the mix.

There are several ways to solder. For example, for difficult joints 'sweat' soldering is the best method. You need to coat both sides of the joint with a layer of solder then bring them together, heating carefully with a low flame whilst the joint is held firmly in place.

Hard solder. This is similar to soft solder but involves much higher temperatures, typically +650°C. The result is a stronger joint. There are two types of hard solder:

Brazing - hardest solder with very high melting point (about 815°C), using alloy of copper and zinc.

Silver - hard solder with high temperatures (650-800°C), using an alloy of s copper and zinc.

In both cases joints need to be held securely, often with wire. An oxy-acetylene welding torch will be used to provide the heat. The flame needs to be bushy rather than narrow so that the flux is not blown away from the joint.

W elding. Welding is the act of fusing together two pieces of into one piece. It is done under very high temperatures using oxy-acetylene gas equipment or electric arc welding one.

When welding, a pool of molten metal is created by the flame and a filler rod is continually dipped into it. The filler rod is the same metal as those being joined and it melts into the joint, thereby filling it and fusing the metal together. In electric arc welding the filler rod is flux coated.

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