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Transistors
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Transistors made it possible to design compact, small-dimensioned electronic devices which consume very little power. The transistors are used for direct transformation of heat energy into electrical energy by means of thermal elements. They are also used to transform radiant energy into electricity with the help of photocells or so called solar batteries. In later years light sources and lasers were built on the basis of transistors.
Transistors revolutionized radio engineering and electronics. Having small size and other properties, transistors make it possible to produce devices which cannot be made with vacuum tubes. Transistors are extremely sensitive to external influences, thousandths of one per cent of admixtures changing their electrical conductive properties by hundreds of thousands times. They are very sensitive to the action of light, nuclear particles, pressure, etc.
Transistors being sensitive to light, engineers have to take this property into consideration. Some transistors act as insulators in the darkness, cadmium sulphide presenting one of them. But already under ordinary room temperature their resistances decrease millions of times. This property was used as the basis for making so called photoresistances. Some of them react not only to visible light but also to ultraviolet, infrared and X-rays, and radioactive radiation. At present such photoresistances, being very small in size, are successfully used as the main elements for various measuring instruments and automatic devices. The supply of transistors is inexhaustible. But up to now only a limited number of them is being used for engineering purposes. Semiconductors are — germanium, silicon, selenium and some of the simple compounds, like lead sulphide and arsenic and phosphoruses with indium and gallium. The electrical properties of germanium may be changed, provided the latter is exposed to light.
A very fine technology has been developed for obtaining transistors with preset physical properties by introducing into them admixtures of gold, copper, nickel, zinc, etc. Scientists have had considerable success in developing special films which protect the transistor crystals from outer influences and change their properties, these films making it possible to create a new family of miniaturized instruments.
III. Translate the text in written form.
WHAT IS CYBERNETICS?
Cybernetics is hard to define. The word "Cybernetics" is known to have originated from the Greek — meaning control. Cybernetics was defined by Wiener as "the science of control and communication, in the animal and the machine, coordination, regulation and control being its themes".
Scientists know cybernetics to be a theory of "machines", but it treats not things but ways of behaving. It does not ask: "What is this thing?" but "What does it do?"
Cybernetics started by being closely associated in many ways with physics. It deals with all forms of "behaviour" in so far as they are regular or determinated, or reproducible. It takes as its subject- matter the domain of "all possible machines". What cybernetic! is the framework1 on which all individual machines may be ordered, related and understood. It is known to have found many applications in different fields of science, technique and economics. It should be kept in mind2 that it offers a single vocabulary and single concepts suitable for representing the most diverse types of systems.
Cybernetics offers one set of correspondences with each branch, science can thereby bring them into exact relation with one another. It has been found repeatedly in science that the discovery that branches are related leads to each branch helping in the development of the other, the result being often a markedly accelerated growth of both. The infinitesimal calculus3 and astronomy, the virus a protein molecules are examples that come to mind. Cybernetics is likely to reveal a great number of interesting and suggestive parallelisms between machine and brain and society. It can provide the common language by which discoveries in the branch can readily be made use of in the others.
Thus, cybernetics provides effective methods for the study, and control of systems that are intrinsically extremely complex. One function of cybernetics is to study the new techniques that are needed in order to enable the scientists to cope with the increasingly complex problems. It deals with ways of making machines; computers and systems operate similarly to the human brain or other biological systems in spite of the brain's being far more efficient than computers in solving certain problems.
Vocabulary notes
1 .framework n — структура
2. it should be kept in mind — следует помнить
3. infinitesimal calculus — бесконечно малое исчисление
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Дата публикования: 2014-11-02; Прочитано: 989 | Нарушение авторского права страницы | Мы поможем в написании вашей работы!
