EMULSIONS
An emulsion represents a disperse system in which the phases are immiscible or partly immiscible liquids.
In nearly all emulsions, one of the phases is aqueous and the other is an oil. If the oil is the disperse phase, the emulsion is termed an oil in water (o/w) one, if the aqueous medium is the disperse phase, the emulsion is termed a water in oil (w/o) one.
If one shakes vigorously a vessel containing two immiscible liquids, both liquids are broken up into droplets whose size depends upon the viscosity of the liquid, surface, interfacial tensions and the vigor of the shaking. As soon as the mechanical dispersive action ceases, the droplets begin to coalesce in order that the total surface free energy may be reduced. Most often, particularly in the case of two pure liquids, the coalescence process is rapid, and within a very few minutes the system consists only of two liquid layers. In the presence of small amounts of additional components, termed emulsifiers, the rate of coalescence of the droplets may be greatly reduced. Emulsions are intrinsically unstable, thus resembling lyophobic colloids. Three distinct kinds of instability are found to exist, each may be of great, importance in industrial products.
Emulsions may "cream", i.e. separate into layers of aqueous phase with a concentrated layer of oil droplets floating on top, the rate depending primarily on the viscosity of the aqueous phase, the size of droplets, and the density difference between the aqueous phase and the droplets. They may also flocculate as do other lyophobic colloids. The floes, being larger than the individual drops, have a higher creaming rate.
NATURE OF ELECTRIC CURRENT
In the modern conception of the constitution of matter it is composed of atoms. The atom is made up of a positive nucleus surrounded by negative charges of electricity, called electrons, which revolve about the nucleus at tremendous speeds. The nucleus consists of a number of protons, each with a single positive charge, and, except for hydrogen, one or more neutrons, which have no charge. The atom is neutral when it contains equal numbers of electrons and protons. A negatively charged body contains more electrons than protons. A positively charged body is one which contains fewer electrons than its normal number.
When the two ends of a conductor are connected to two points at different potentials, such as the terminals of a battery, we say that there is an electric current in the conductor. What actually happens?
The conductor has equal numbers of positive and negative charges in its atoms, and we want to know how the charges can be made to produce a current. The atoms in metals are packed so closely that they overlap to some extent, so that it is comparatively easy for the outer electrons to pass from one atom to another if a small force is applied to them. The battery causes a potential difference between the ends of the wire, and thus provides forces that make the negative electrons in the wire move toward the point of higher potential. This electron flow toward the positive electrode is the electric current. Naturally, materials differ considerably in the ease with which electrons can be made to migrate from atom to atom.
The current will not flow unless there is an electric circuit. The magnitude of the current depends simply on the rate of flow of electrons along the conductor.
RELAY COMPUTERS
Even in the 40s the primary speed limit on these rudimentary computers was mechanical, so developers looked to other technologies to build their computers. Bell Telephone Laboratories began work on relay-based computers in 1938. A relay is an electrically controlled switch-one source of electricity activates an electromagnet which operates a switch which, in turn, alters the electrical flow in another circuit. Relays are a hybrid technology, electro-mechanical. Their mechanical side performs physical work while their electrical nature makes them very flexible. One relay can control other$ almost unlimited in number and distance. The gears and levers of purely mechanical calculators are limited in reach in both regards.
The choice of relay technology was a natural one for the telephone company. After all, the telephone switching systems of the time made extensive use of relays-rooms and rooms filled with them.
Information science with the ideas and message of processing and storing information is of great importance today. That's why computer technology must be told in secondary school. The new subject 'basic information science', and 'computing machine' was introduced for the senior forms at schools. The pupils teach computers to investigate school problems. Contact with the machine increases the interest in learning, makes them more serious about studying new subject. School computers are used not only for studying information science, but also examinations purposes. Young people who finish the school must be trained to operate computers.
Automatic control
History provides very early examples of automatic control, but they were little used in industry. Progress was slow until last century, but it received an important stimulus from the military needs of the last war and the pace has accelerated. Automatic control is most advanced in industries like chemicals, oil-refining and food-processing, where materials are easy to handle. Because of it these industries have become highly automatic without any of the well-known inventions, such as transfer-machines and electronic computers. Control is also largely automatic in the manufacture of goods so different as iron and steel, cement and paper.
A system of control usually consists of three basic units – one that measures, one that controls, and one that corrects. If, for example, the condition to be controlled is the temperature of the boiler, the measuring unit records what is happening to the temperature and tells the controlling unit, which compares the actual temperature with what it should be and then tells the correcting unit to adjust a steam valve and so correct the temperature.
Controlling instruments are pneumatic, mechanical or hydraulic, and electric. Electric or electronic units are fast and able to send signals over long distances so giving "remote" control.
Automatic control is perhaps best known in plants where production is continuous, such as oil-refineries, but it is also found in factories that produce in batches.
Engines
Do you know what the first engine was like? It was called the "water wheel". This was an ordinary wheel with blades fixed to it, and the current of a river turned it. These first engines were used for irrigating fields.
Then a wind-powered engine was invented. This was a wheel, but a very small one. Long wide wooden blades were attached to it. The new engine was driven by the wind. Some of these one can still see in the country.
Both of these, the water- and wind-operated engines are very economical. They do not need fuel in order to function. But they are dependent on the weather.
Many years passed and people invented a new engine, one operated by steam. In a steam engine, there is a furnace and a boiler. The furnace is filled with wood or coal and then lit. The fire heats the water in the boiler and when it boils, it turns into steam which does some useful work.
The more coal is put in the furnace, the stronger the fire is burning. The more steam there is the faster a train or a boat is moving.
The steam engine drove all sorts of machines, for example, steam ships and steam locomotives. Indeed, the very first aeroplane built by A.F. Mozhaisky also had a steam engine. However, the steam engine had its disadvantages. It was too large and heavy, and needed too much fuel.
The imperfections of the steam engine led to the design of a new type. It was called the internal combustion engine, because its fuel ignites and burns inside the engine itself and not in a furnace. It is smaller and lighter than a steam engine because it does not have a boiler. It is also more powerful, as it uses better-quality fuel: petrol or kerosene.
The internal combustion engine is now used in cars, diesel locomotives and motor ships. But to enable aeroplanes to fly faster than the speed of sound another, more powerful engine was needed. Eventually, one was invented and it was given the name "jet engine". The gases in it reach the temperature of over a thousand degrees. It is made of a very resistant metal so that it will no melt.
Getting into Deep Water
The dark depths of the Gulf of Mexico, once frequented by only the sea creatures, are now alive with human activity. Miniature submarines and robot-like vehicles move around the ocean bottom while divers make their way around incredible underwater structures -taller than New York City skyscrapers but almost totally beneath the surface of the waves. Modern-day explorers are using technology worth of Jules Verne and Jakques Cousteau to find fresh supplies of oil and natural gas.
Until recently, drilling in the Gulf was concentrated close to shore in water as deep as 9 m. But now the scientists are looking to hundreds of meters deep and 160 km and more from land.
The deep water research began in 1984. Since many American companies have built the world's deepest production platforms of more than 100 stories high. Finding gas and oil deposites at large depth is not an easy technological task.
Laser Technology
In the last decade there was outstanding progress in the development of laser technology and its application in science, industry and commerce. Laser cutting, welding and machining are beginning to be big business. The market for laser systems represents around 2,5 % of the world machine tool market.
Which country is the biggest producer and consumer of lasers? Why, Japan, naturally: Japan produced 46% of world's lasers in 1989, while figures for Europe and the USA are 32% and 22%. Japan is building 1 200 to 2 000 CO2 lasers per year of which some 95% are over 500 W power and 80% of them are used for cutting operations.
Europe is the second largest user and the third largest producer. In 1990 Europe's market for lasers was $ 128 million, of which Germany consumed about $ 51 million, and Italy – $12 million. The Germany met 90% of its demands through domestic producers. Growth rate of the European market is estimated at 10 to 15% per year.
In future the main trend influencing the industry will be laser source prices. The prices are dropping. There appear lasers of modular construction. The complexity of laser machines is rising. Multi-axes systems are in more use now. Recently 7-axis CNC laser machining center has been introduced. In addition to X, Y and Z axes, there are two rotary axes, A and C, and two more linear axes, U and V, to give a trepanning motion to the laser.
Space Cooling
A new method of cooling that can generate cryogenic temperatures of 200° С below zero without the use of electricity and with almost no moving parts has been tested at the jet propulsion Laboratory in Pacadena, California. The refrigerator used for the purpose was recently tested to –253° C, only 20 degrees above absolute zero, the lowest possible temperature.
In space such cooling system could increase the life of future space station refueling ports by cooling the large liquid-hydrogen fuel tanks which are likely to be in service.
In future earth applications it could be used for cooling hydrogen-powered cars and planes, as well as for cooling superconducting motors and computers.
According to JPL (Jet Propulsion Laboratory) experts the key lies in the use of hydrides, materials that interact with hydrogen. These materials absorb tremendous amounts of hydrogen gas at room temperature. The engineers of JPL have taken advantage of this property to build a series of devices that act as compressors and provide a continuous cooling stream of liquid hydrogen.
The system saves weight in space since it can use direct solar heat instead of electricity from heavier, inefficient electric systems. Because it has so few moving parts and uses the same supply of gas in a closed cycle, it could operate for many decades. Because of its long potential lifetime, the system could be used to cool infrared sensors' during missions to the other planets, which may take 10 years or more to complete.
