Вариант № 3

(Автоматизация)

Application of automated guided vehicle (AGV)

The maintenance requirements include the recharging of batteries and the usual checks of the motor, the safety devices (such as horns, bumpers, sensors), the on-board controller, communication links and so on. Most systems are equipped with automatic battery-condition report facility connected to a central computer, which directs vehicles to a battery charging station before power fails. Typically, AGV can work up to eight hours without battery recharge.

Environment requirements should also be taken into account, namely: the guide path is reliable if properly sealed and laid in the floor although expansion joints can cause some problems. The shop floor should be dry during operation because the carts may slip and slide. Lift tracks, if used within the same area, can damage floor control elements of AGVs so extra attention is required.

The load to be considered includes size, weight and stability. If pallets are transported, the maximum part weight is reduced by the weight of the pallet itself which is usually relatively high. The clearance provided for vehicle and its load should be at least 100 mm on each side.

(Промышленная электроника)

Storage hardware

The purpose of storage hardware is to store computer instructions and data in a form that is relatively permanent and. Storage hardware serves the same basic functions as do office filing systems except that it stores data as electromagnetic signals. The most common ways of storing data are Hard disk (HDD), floppy disk and CD-ROM.

Hard disk is a rigid disk coated with magnetic material, for storing programs and relatively large amounts of data.

Floppy disk (diskette) - thin, usually flexible plastic disk coated with magnetic material, for storing computer data and programs. There are two formats for floppy disks: 5.25" and 3.5". 5.25" is not used in modern computer systems because of it relatively large size, flexibility and small capacity. 3.5" disks are formatted 1.44 megabytes and are widely used.

CD-ROM (compact disc read only memory) is a compact disc on which a large amount of digitized read-only data can be stored. CD-ROMs are very popular now because of the growing speed which CD-ROM drives can provide nowadays.

(Электроснабжение)

Capacity

A capacity is one of the main elements of a circuit. It is used to store electric energy. A capacitor stores electric energy provided that a voltage source is applied to it.

The main parts of a capacitor are metal plates and in this way to prevent a short.

In the diagram one can see two common types of capacitors in use nowadays: a fixed capacitor and a variable one. The plates of a fixed capacitor cannot be moved; for this reason its capacity does not change. The plates of a variable capacitor move; its capacitor changes. The greater the distance between the plates the less is the capacity of a capacitor. Variable capacitors are commonly used by radiomen; their function is to vary the frequency in the circuit. Fixed capacitors are used in telephone and radio work.

Fixed capacitors have insulators produced of paper, ceramics and other materials; variable capacitors have air insulators. Paper capacitors are commonly used in radio and electronics; their advantage is their high capacity: it may be higher than 1,000 picofarad.

Besides, electrolyte capacitors are highly in use. They also have a very high capacity: it varies from 0,5 to 2,000 microfarad. Their disadvantage is that they change their capacity when the temperature changes.

(Химия)

Mechanism of corrosion

The element iron when placed in contact with water or a solution has an inherent tendency to go into the solution in the form of ions, but since the solution must remain electrically neutral, these positive ions can enter the solution only if an equivalent number of positive ions of some other element are somehow displaced. In the case of iron immersed in water, the element displaced is hydrogen which forms a thin invisible film thereby protecting the further action to some extent.

If corrosion is to proceed, the hydrogen film must be removed which can happen in two ways: (a) the hydrogen combining with oxygen present in the solution to form water, or (b) it may escape as bubbles of hydrogen gas. In general, the rate of destruction of this film is determined by the effective concentration of dissolved oxygen in the water next to the metal and this in turn depends upon factors such as the degree of aeration of the water (whether at rest or in motion), temperature, and salts present, etc.

In acid solution the reaction is identical, but the film is removed mainly as bubbles of gas. This happens because the tendency of the hydrogen to plate out from a solution increases with the degree of acidity of the solution to such an extent that the pressure in the gas film suffices to form bubbles. This accounts directly for the fact that corrosion is more rapid in more acid solutions and less rapid in more alkaline solutions.

(Машиностроение)

Technological processes

Sheet metal forming is widely used when parts of certain shape and size are needed. It includes forging, bending and shearing. One characteristic of sheet metal forming is that the thickness of the sheet changes little in processing. The metal is stretched just beyond its yield point in order to retain the new shape. Bending can be done by pressing between two dies. Shearing is a cutting operation similar to that used for cloth.

Forging is the shaping of a piece of metal by pushing with open or closed dies. It is usually done hot in order to reduce the required force and increase the metal's plasticity.

Open-die forging is usually done by hammering a part between two flat faces. It is used to make parts that are too big to be formed in a closed die or in cases where only a few parts are to be made. The earliest forging machines lifted a large hammer that was then dropped on the work-piece, but now air or steam hammers are used, since they allow greater control over the force and the rate of forming. The part is shaped by moving or turning it between blows.

Closed-died forging is the shaping of hot metal within the walls of two dies that come together to enclose the work-piece on all sides. The process starts with a rod or bar cut to the length needed to fill the die. Since large, complex shapes and large strains are involved, several dies may be used to go from the initial bar to the final shape. With closed-dies, parts can be made to close tolerances so that little finish machining is required.

(Гражданское строительство)

Fire Walls

The function of a fire wall is to form a required separation in order to restrict the spread of fire through a building.

Every fire wall should extend from the foundation of a building to its roof. Every fire wall is supplied with an opening. It is of great importance to note that openings should be strictly restricted in size. Besides they must be closed with fire doors or wired glass.

A fire separation wall, like a fire wall, forms a required separation to restrict the spread of fire through a building. But, unlike a fire wall, a fire separation wall does not extend from foundation to roof. Openings in fire separation walls are also restricted in size and must be closed with fire doors or wired glass.

Fire separation walls are used to divide a building between mixed occupancies and for enclosure of stairways and exit way corridors.

Shaft walls are used to enclose a multistory open space in a building. To shaft walls belong elevator shafts, conduits, or pipes.

Walls for elevator shafts must be strong enough to bear air pressure and loads placed on them by the movements of the elevator cars within the shaft. Also, it is of importance to note that the noise of elevator machinery must be prevented from reaching other areas of the building.

(Экология)

Ecosystems: What keeps them the same?

The most important point to recognize is that no forces or rigid structures exist that prevent ecosystems from changing. In fact, ecosystems can and do change, even drastically as conditions are altered. The one thing that enables ecosystems to sustain a given composition of species over long periods of time is that all the relationships in the system are in a dynamic balance.

Each species in an ecosystem exists as a population – that is to say, an interbreeding, reproducing group. An ecosystem's remaining stable (sustaining itself) over a long period of time implies that the population of each species in the ecosystem remains more or less constant in size and geographic distribution. Any continuing increase or decrease in population would be observed as a change in the ecosystem. In turn, a population's remaining constant over a long time means that reproductive rate is equaled by death rate. Thus, the problem of ecosystem balance boils down to a problem of how birth rate and death rate are balanced for each species in the ecosystem.

Maintaining or increasing a population depends on more than reproductive rate (number of live births, eggs laid, or seeds or spores set in plants) by itself. Recruitment, which is defined as making it through the early growth stages to become part of breeding, reproducing population, is equally important. Conversely, even a relatively low reproductive rate may result in a substantial population increase when recruitment is high.

(Автомобилестроение)

The Wankel engine

The Wankel engine is form of heat engine which has a rotary piston. In other words, instead of going up and down the Wankel piston rotates in the cylinder. Both cylinder and piston are quite different in shape from those of conventional engines. The Wankel piston is triangular with curved sides and the cylinder is roughly oval in shape. The piston has an inner bore which is linked through an eccentric gear to the output shaft. The other end of the bore is toothed and engaged with a stationary gear fixed to the cylinder end. This arrangement ensures that the piston follows an elliptical path round the cylinder so that the apexes of the piston which carry gas-tight seals are always in contact with the inside surface of the cylinder.

The piston thus forms three crescent-shaped spaces between itself and the cylinder wall, which vary in size as the piston rotates. Fuel enters the cylinder through the inlet port when one of these spaces is increasing in size. The fuel trapped in this section is then compressed by the turning piston and ignited by the sparking plug. The expanding gases subject the piston to a twisting moment which makes the piston revolve further until the exhaust gases escape through the exhaust port. A fresh charge is then induced into the cylinder. Meanwhile the same process is being repeated in the other two spaces between the piston and the cylinder.

(Экономика)

The budget

The budget is an estimate of national revenue and expenditure for the ensuing fiscal year. When expenditure exceeds the revenue the budget has a deficit.

Revenue and expenditure forecasting is the most fundamental step in the process of budget preparation. Adequate planning of recurrent and capital expenditure depends critically on an accurate forecast of revenue availability. The determination of the expected overall deficit in the public sector and therefore the macroeconomic impact of fiscal policy requires accurate forecast of tax collection and expenditures.

In Russia, public finance is a sum of budgets of all levels of subjects of the Federation, extrabudgetary and reserve funds.

An accurate revenue forecast is most critical at the federal level of government but it is also important for all subnational governments because over the last several years they have worked with increasingly autonomous budgets.

Budget preparation at the federal level involves a number of institutions. The Ministry of Finance (MoF) is the central coordinating institution in charge of compiling and presenting the budget. It has major inputs from ministries in various sectors of the economy and the state tax bodies.

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