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Dear Sirs
We recently attended the Software Trade Exhibition in Bath, and were impressed by the range of software available through your company.
We are a large chain of business software retailers and are looking for a software house which could supply us with a range applications programs. As we usually place large orders, we would expect a quantity discount in addition to a 20 p.c. trade discount off net list prices. Our terms of payment are normally 30 days after receipt of invoice.
If these conditions are of interest to you, we would be much obliged if you could send us your current catalogue and price list. We look forward to hearing from you soon.
Yours faithfully
P. Barker
Purchasing Manager
Рекомендованная литература: 1. ОЛ (с.26-27).
Тексты для самостоятельной работы
Вариант 1
Text 1
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In addition to the lumber cutting in the mill, presawing preparation of logs and post sawing control of lumber seasoning and other general services are part of sawmill activity.
Sometimes the outside-mill activity requires more than half of the total labour force. Therefore it is important to have this outside-mill operation well-organized and mechanized.
Usually the logs are cross-cut before entering the mill. For this operation the portable electric chain saws are most convenient. It is preferable to debark some species with heavy bark usually containing sandy particles. For such cases a mechanical debarker should be used.
If a sawmill cuts a major portion of species susceptible to fungus or insect attack, a mechanized tank for dipping treatment should be installed at the remote end of the "green" chain.
Transport and stacking of lumber for air seasoning usually requires a sizeable labour force. The most economical method is to stack the lumber for air seasoning immediately after removing it from the "green" chain. The piles should be of a convenient size for transport by fork-lift. Correct seasoning is a very important sawmill's activity. Whether kiln or semi-artificial seasoning should be a part of the post-sawing treatment, or natural air seasoning is enough, can be decided according to particular requirements.
Text 2
The designer of a sawmill faces many limitations. He must consider the natural and economic conditions and the limited choice of machines. These two factors usually decide the size of the mill and the degree of mechanization.
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So far as the equipment is concerned, we note the following:
1)Bandsaws are the most versatile. There is practically no sawing operation they cannot handle. Selection of the size of the saws is made with a view to ensuring that the strength of the blade is commensurate with the stress to which it is subjected. In the first sawing of soft woods, six-foot bandsaws are always used, with harder woods bigger saws are necessary. In resawing, a bandsaw with a rack carrier may be employed where the use of a gang saw is not possible.
2)The circular saw has limited capacity. Its advantage resides in the fact, that it can be fitted with high-speed steel teeth that make it possible to use it in the sawing of both very hard and soft woods. Its use is limited, particularly in the second sawing, because of the waste of raw material it entails.
3)The gang saw, like the bandsaw, can be used in either rapid or slow sawing. It is very valuable in rapid sawing, which is rarely-done, except in the second sawing of planks 20-50 centimeters thick. Slow sawing is almost obligatory in the first sawing. It may, however be acceptable in certain other cases. Gang saws or frame saws, as they are also called, gives the highest accuracy. So frame-sawn lumber can be used for building purposes without previous planning which means a saving both in labour and material.
Text 3
Historically, the first phase in the manufacture of wood products has been air drying and kiln drying of lumber. There are many methods that have been used over
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the years to dry lumber from the green state to a dry condition suitable to its end use. There was an era when furniture factories air-dried their lumber for one year or more, then placed it in dry storage for almost another year to bring the lumber down to a moisture content with, which to make furniture. Degrade was rather high, but the price of lumber was low.
The next step was the same air-drying. Then natural draft kilns were used to shorten the time of drying and provide moisture content usable for furniture. These natural draft kilns were generally cross-piled, and there are a few still existing. Most of them have been modified.
The next step to further cut down time in the kilns was double-attack air drying kilns with a new innovation, automatic control of heat, humidity and ventilation
For years the forest industry has used natural solar drying and steam drying of lumber. Today a combination of air drying by means of low temperature kilns, or a predrier, and the modern dry kiln has made drying of green hardwoods possible in a relatively short time and with little or no degrade. Drying of hardwood lumber for furniture manufacture is an expensive and time-consuming operation. Looses in drying due to hecks, cracks, splits and warp can easily exceed the operating costs and result in a loss of raw material and wasted time and labor. Extensive technology, aimed at reducing degrade and drying, times, has recently been introduced to the kiln industry. These innovators include the use of vacuum pressures, microwaves, heat pumps. Four drying methods have come to use as ways to reduce drying losses, shorten drying times and reduce costs. They are 1) Predrying, 2) Dehumidification Drying, 3) Vacuum Drying, 4) Radiofrequency Drying.
Text 4
Solar drying kilns apply the principles used in a greenhouse to the drying of timber. Heat is trapped inside a structure covered with a material which is transparent to short wave radiation (light) and not transparent to longer wave radiation (heat) and
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which at the same time reduces heat loss by conduction and convection. The differences between a greenhouse and a solar kiln are, however, important. They are as follows:
1)A solar kiln may trap as much heat as possible whereas a greenhouse may not.
2)Air circulation is essential in a solar kiln to remove water from the wood surface whereas convection gives sufficient air circulation in a greenhouse.
3)Temperatures increase and humidity decreases in a solar kiln as the timber dries whereas, in a greenhouse, the more constant they remain the better.
Solar kilns vary considerably in size and design but most of them are modifications of a simple greenhouse-type structure. The characteristics of solar kilns are as follows:
1)Drying from green to 12 per cent moisture content takes 2-3 times as long as in a convectional kiln (which is usually steam heated).
2)Drying is normally twice as fast as air drying and equilibrium moisture content varies between 6 and 12 per cent.
3)Quality of drying in solar kilns is high for the following reasons: a) general rate of drying is slow compared with convectional kilns, b) daily variations in temperature are larger than with air drying but variations in humidity are much lower. It should be noticed that with solar drying it is possible to dry timber to 8-10 per cent equilibrium moisture content.
The advantages of solar kilns are therefore: high quality-drying particularly for woods that are slow and difficult to dry, low coats and low level of skill required to operate them. They are simple to erect and energy-saving. Their disadvantages are that they are slow compared with convectional kilns and dependent on the weather.
Вариант 2
Text 1