II. Перепишите вопросы к тексту и письменно ответьте на них. Переведите вопросы и ответы на русский язык.

1. When was the technology of powder metallurgy created?

2. What important feature has powder metallurgy?

3. Where does powder metallurgy find application?

4. What is the source material for this technology?

5. What properties have parts made of metal powder?

Вариант II

I. Перепишите и письменно переведите текст. Crystals

Speaking about crystals one often imagines something beauti­ful, perfect and rare. In reality, however, practically all solid bodies around us are crystals. The exceptions are plants, animals, water and the atmosphere".

Till recently, crystallography was regarded as "the most dreary, the most difficult, and the most useless of sciences”. Today crystallog­raphy is one of the most important branches of natural science, rich in practical achievements, having deep philosophical content. It is closely related to mathematics.

By now several thousand inorganic and over five thousand or­ganic crystal structures have been studied.

Not long ago only X-rays* were used for structural analysis. And now the method of neutron diffraction has come into wide use in the field of crystal analysis.

Crystals offer a simple way for transforming one kind of energy into another, for instance, by using the action of light to obtain an electric effect, or to achieve optical effects by mechanical action. It is possible to illuminate a crystal with red light and make it emit green rays, In fact, in modern technology all the instruments that can emit energy are built around crystals.

Of special interest is research into the strength of crystals. All metals and alloys constitute a collection of variously placed tiny crys­tals. The more perfect the crystals, the higher the strength of the metal. This means that by special methods it is possible to obtain crystals of required strength.

II. Перепишите вопросы к тексту и письменно ответьте на них. Переведите вопросы и ответы на русский язык.

1. What kinds of matter are not crystals?

2. What branch of science does crystallography belong to?

3. What science is crystallography closely related to?

4. What methods are used for crystal analisis?

5. What crystals do all metals all alloys cousist of?

Вариант III

I. Перепишите и письменно переведите текст. The Promising Field of High-Pressure Research

Subjecting materials to high pressure greatly changes their properties. When compressed under more that 500.000 pounds per square inch ordinary liquids become solids. Gases become liquids. Some rocks stretch like rubber. Insulating materials begin to conduct electricity. Water freezes at room temperature into dense heavy cubes which explode violently when the pressure is suddenly released.

The most interesting discovery in connection with high-pressure research is the artificial conversion of graphite to diamonds.

The interior of the earth itself is a high-pressure laboratory. The pressure at the centre of the earth is estimated to be 3.000 kilobars.¹ Graphite subjected to the tremendous heat and pressure generated deep below the earth's surface turns to diamond in the course of thou­sands or, perhaps, millions of years. Today total output of synthetic diamonds in the world amounts to several tons annually.

Metals become increasingly conductive under high pressures. This has led some scientists to suggest that increasingly high pressures might cause some metals to become superconductive at room tempera­ture. Superconductivity, the complete absence of electrical resistance, has numerous potential scientific applications, but can now be ob­tained only at extremely low temperatures close to absolute zero.