Страдательный залог. Модальные глаголы

Упражнения.

I. Переведите на русский язык предложения:

1.The term supersonic is no longer used as a synonym for ultrasonic. 2.The piezoelectric effect was first discovered by the Curie brothers in 1880. 3.The first important use of ultrasonics was made during 1914-18 war for underwater soundings. 4.After 1939-1945 war more important advances were made in ultrasonics. 5.At the same time considerable advances were made in the application of high-energy ultrasonics to industrial and medical progress. 6.The deflection of beams is influenced by field intensity and by other factors. 7.Experimental application of radioisotopes was followed by their industrial use. 8.The advantages of synchrotrons were much spoken about at the research institute. 9.The quality of colour television was much spoken about at that conference. 10.Receiving station operation is greatly influenced by various factors.

II. Переведите на русский язык предложения, содержащие модальные глаголы и их эквиваленты:

1.There is a lower and an upper limit to the frequencies the ear can detect. 2.The subject may be divided into two sections, one dealing with low-amplitude vibrations and the other with high energies. 3.Two types of crystals may be used for generating ultrasonic waves. 4.It should be mentioned that the discovery of radar led to the development of thepulse technique. 5.If necessary, the transducer can work at far higher-frequencies. 6.The designers can always improve the operation of these receivers. 7.He could use any transmitter for this system. 8.We have to increase the current strength by decreasing the resistance of the circuit. 9.The designer was able to construct a new device by using semiconductors. 10.The engineers were to investigate new means of radio communication. 11.They didn't have to analyze these data. 12.The students might use all the laboratory equipment.

ULTRASONICS

Ultrasonics is the name given to the study and application of sound waves having frequencies higher than those to which the human ear can respond. The term supersonic is no longer used as a synonym for ultrasonic because of its other meaning in hydrodynamics. Thus, ultrasonics is the science of inaudible sound. There is alower and an upper limit to the frequencies the ear can detect. The piano string called middle С vibrates 256 times a second - 256 cycles. A typical human ear has a range from 50 to 20,000 cycles per second.

The subject may be divided into two sections, one dealing with low-amplitude vibrations and the other with high energies. For low amplitude propagation one is concerned with the effect of the medium on the waves; it is known that permanent changes do not take place in the medium. For high-energy application, however, one is concerned with changes brought about by waves in the medium.

One of the first applications of ultrasonics was in 1883 when Dalton worked out a high-frequency whistle to measure the upper frequency limit of response of the human ear. Even at this time both the piezoelectric and magnetostrictive effects were known, but it was not until a sufficient degree ofprogress was made in the study of electrons that they could be used for generating ultrasonics.

Now it is well known that two types of crystals maybe used for generating ultrasonic waves, one of which displays the piezoelectric effect and the other the electrostrictive effect which is analogous to magnetostrictive.

The piezoelectric effect was first discovered by the Curie brothers in 1880. It occurs in crystals having axes on non-symmetry. The electrostrictive effect occurs in all dielectrics.

It is interesting to note that the first important use of ultrasonics was made by Langevin during the 1914-18 war for underwater soundings. Then slow but steady progress was made in the measurements of propagation constants of materials.

It was not until after the 1939-45 war that any more important advances were made in ultrasonics. It should be mentioned that the discovery of radar led to the development of the pulse technique and its application to the non-destructive testing of materials and the medical diagnosis. At the same time considerable advances were made in the application of high-energy ultrasonics to industrial and medical processes.

Nowdays one calls any device which changes sound into an audio signal or vice versa as a transducer.

The sensitivity of the linear transducer is the ratio of output electric signal to input audio-signal. For many ultrasonic applications quartz possesses most or all of desirable properties of a transducer. If necessary, the transducer can work at far higher frequencies where sound begins to show unaccustomed vigour.

These vibrations have many uses, but two examples must do. The ultrasonic washing machine is simply alow-power transducer which one can dip into any kitchen sink. The wave shakes the water gently but quickly to take away the dirt from clothes or the dishes. An ultrasonic drill can penetrate through brittle materials to give a hole of any desired shape.

Лексико-грамматический комментарий

ultrasonics – ультразвуковая техника; ультраакустика

respond – отвечать, реагировать

response – ответ, реакция, отклик, отзвук

no longer – больше не

because of – из-за, благодаря

range – диапазон, предел

deal(with) – иметь дело, рассматривать, касаться(вопроса)

propagation – распространение

to be concerned with – заниматься чем-либо, интересоваться

to bring about – вызывать

to work out – разрабатывать

magnetostrictive effect – магнитострикционный эффект

electrostrictive effect – электрострикционный эффект

underwater sounding – подводное измерение, зондирование

It should be mentioned – следует упомянуть

non-destructive testing – неразрушающее испытание

unaccustomed vigour – необычная сила, непривычнаяэнергия

Вопросы и задания.

I. Дайте ответы на следующие вопросы:

1. What is ultrasonics?

2. What is a lower and an upper limit to the frequencies the ear can detect?

3. What has Dalton worked out?

4. What types of crystals may be used forgenerating ultrasonic waves?

5. When was the piezoelectric effect first discovered and bywhom?

6. When was the first important use of ultrasonics made?

7. What has the discovery of radar led to?

8. Is ultrasonics applied to industrial and medical processes?

9. What is a transducer?

II. Верны ли следующие утверждения?

1. Ultrasonics is the name given to the study and application of sound waves.

2. The term supersonic is used as a synonym for ultrasonic.

3. Ultrasonics is the science of inaudible sounds.

4. For low-amplitude propagation one is concerned with the effect of the medium on the waves.

5. Dalton's whistle didn't measure the upper frequency limit of response of the human ear.

6. The first important use of ultrasonics was made for underwater soundings.

7. The discovery of radar led to the development of the pulse technique and its application to the non-destructive testing of materials and the medical diagnosis.

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