12. Make up a dialogue on the following topics using the Infinitive as well as the intriductory and connective words.

1. Variety of cranes. Their principal parts. 3. Their distinctive features.

13. Consider the notion and it’s definition and tell what you know on the topic.

The Integral

The first basic concept of the calculus is that of integral. In this

a rticle we shall understand the integral as an expression of the area under a curve by means of a limit. If a positive continuous function y = ƒ(x) is given, e. g. y = x² or y = x ²+ cosx, then we consider the domain bounded below by the segment on the x-axis

from a coordinate a to a greater coordinate b,

on the sides by perpendiculars to the x-

axis at these points, and above by the

curve (see Fig. 27). Fig. 27

y=ƒ(x). The integral as an area.

Our aim is calculating the area A of this domain. Since such domain cannot, in general, be decomposed into rectangles or

triangles, no immediate expression of this area A is available for explicit calculation. But finding an approximate value for A is possible,

and thus we can represent A as a limit in the fol­lowing way: by subdividing the interval from x = a to x ─ b into a number of small

subintervals.

It can be done by erecting perpendi­culars at each point of subdivision, and by replacing each strip of the domain under the curve by a rec­tangle. The height of those rectangles is chosen somewhere between the greatest and the least height of the curve in that strip.

The sum S of the areas of these rectangles gives an aproximate value for the actual area A under the curve.

Text 2

1. Read the text and classify conveyers. Translate the text.

Conveyer

Conveyer (Amer. conveyor) is a device for moving loads from one point to another over fixed paths. Conveyors are used throughout industry in nearly every phase of production and distribu­tion, since they promote economy by providing a controlled continuous flow of materials. The conveyor has become a

symbol of mass production. There are about 130 different types of conveyors.

Nonpowered Conveyors. The simplest types of conveyors are those that use gravity or manual power to propel the objects. The most common nonpowered conveyors are chutes, roller convey­ors, and wheel conveyors.

Chutes. Certain bulk materials, such as coal and gravel, and some

solid objects that are not free flowing can be directed and lowered by

gravity in troughs called chutes. Chutes are usually used for short moves,

such as from one machine to another or from one floor to another.

Objects are advanced by gravity or manually on roller conveyors,

which consist of a series of rollers supported in a frame. Inclined roller

convey­ors depend on rolling friction to control the speed of descent of the

materials. Roller convey­ors are extremely common in package-handling

operations. Wheel Conveyors are similar to roller conveyors but have skate-type wheels mounted on parallel bars.

Powered Conveyors. Most conveyors use power to move materials, and employ a belt, chain, or cable to provide the material movement.

Belt Conveyors consist essen­tially of an endless belt of fabric, rubber, plas­tic, leather or metal. The belt is supported on rollers, troughing idlers, or a flat slider bed and passes over a drive and end pulley. Loads such as cartons, bags, and boxes are carried on the belt. In Live-Roller Conveyors rollers are power driven. Apron Conveyors consist ot a number of overlapping steel plates, aprons, or pans, attached at their ends to two strands of chain that ran in steel guides, and consists of wood or metal slats attached at their ends to two sliding chains. The slat conveyor is a variation of the apron conveyor. Bucket Conveyors carry materials in buckets mounted on an endless belt or on one or two chains. Flight Conveyors. In flight conveyors, flight or scrapers are attached at spaced intervals to one or more endless chains or cables. Flight con­veyors are generally used to push bulk materials

along a trough.

Trolley Conveyors. Trolley conveyors consist or a series of trolleys that are supported by a single overhead track. They are connected to and pro­pelled by a chain, cable, or other linkage. The loads are usually placed in carriers that are sus­pended from the trolleys

Power-and-Free Conveyors. The power-and-free conveyor is a system in which the load is moved in carriers that are supported by a single rail (monorail). The carriers are connected to and propelled by a trolley conveyor

that is directly above the "free" rail.

Floor conveyor is commonly used in auto­mobile industry.Tow Conveyors pull floor-supported trucks or carts. A chain conveyor

pushes logs under jets of water for cleaning before processing at a newsprint mill. The screw conveyor can have its flights so shaped that it

mixes ma­terials while conveying them.

screw conveyer chain conveyer belt conveyer

Fig. 28