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Off-road transport of timber was traditionally based on use of the horse and sledge in winter. When the mechanization in forestry began, farm tractors were tried in off-road transport of timber. The farm tractor, however, required the opening and leveling of a strip road. In horse transport, the sledge was taken right up to the stump, whereas in tractor transport, it became necessary to carry pulpwood manually or winch by tractor to strip road.
The farm tractor needed accessory equipment to perform off-road transport. The most important were half-tracks, powered semi-trailers, winches and winchdriven boom loaders.
The four-wheel-drive cable skidders proved to be far superior to the farm tractor. However, skidders were designed for the tree-length harvesting system, and they were inefficient in transporting small-sized stems bucked timber.
Soon work began to develop a tractor better suited to forest management systems and thinning operations. In the mid-1960s, a large-wheeled, load-car ring forwarder, typically equipped with a hydraulic knuckle-boom loader, was created. The forwarder, solved the problem of mechanization of off-road transport. Today most limber is brought to the road side by medium-sized 10-12t forwarders. In the late 1980s, lighter forwarders and light rubber-tracked, load-carrying crawlers were developed primarily for peat land logging and for early commercial thinnings.
The forwarder has become an internationally recognized forest machine. It is characterized by high productivity, flexible mobility from site, and is environmentally considerate.
Text 2
Forest industry companies purchase most of their timber standing. The purchasing forest industry is responsible for the planning and organization of the logging operations. The manual labour, forest machine contractors, and truckers are
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hired separately. The other part of the wood raw material is delivered as timber assortments at the road side by small forest owners.
Traditionally and still today, sub-operations of a logging system are kept independent of each other by using buffer storage at the stump or road side. This cold decking helps to increase the operational ability and system productivity. Hot logging schedules are avoided.
The tree-length method today represents little of the off-road transport of timber. The log-length method and load-carrying tractors have proved their superiority. Due to the small size of the forest holdings there is generally a shortage of landing areas.
Forwarders are capable of storing the timber with the crane in up to 4m high piles thus reducing the landing area requirement radically. In the longlength method the load-carrying tractors sort tne timber and pile it in conjunction with unloading site according to assortment. This cold decking makes it easy for the trucks to deliver different assortments to different mills. Thus, loading time is decreased, criss cross transport is reduced, and handling of timber at the mill yard becomes easier.
Modern logging machines apply advanced technology and require high operator skills and careful maintenance. The operators must be able to carry out emergency repairs.
The long-distance transport always starts with a truck, generally equipped with a full trailer. When the hauling distance is long, the truck transport often continues by rail or floating.
Text 3
In motor-manual methods the tree is felled, delimbed and bucked in to final lengths with a chainsaw at the site in accordance with the quality requirements
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applied, and small-sized pulpwood logs are bunched. The length of pulpwood varies usually between 3-5m and that of sawlogs between 4-5m.
In mechanized methods multi-function machines which are classified in three main groups replace chainsaw operators: feller-bunchers, processors, and harvesters. The feller-bunchers perform only felling and bunching. Processors carry out delimbing and bucking, thus chainsaw operators or feller-bunchers are required for felling. Harvesters are also of felling the trees.
The first generation of these multi-function machines were double-grip harvesters, which first sever the tree from the stump with a crane-mounted felling head and then transfer it for further processing to a separate mechanism mounted on the base carrier. A more common option is presently the single-grip harvester, which uses a relatively light, crane-mounted head for both felling and bucking. The majority of the new machines are crane-mounted single-grip harvesters. Double-grip harvesters have their primary application in larger trees because of their robust structure and higher productivity.
Compared to motor-manual methods, multi-function machines are economically competitive particularly in final fellings, in large-scale operations, for large trees, and especially for trees with a long live crown such as spruce. However, light multifunction machines, designed for smaller trees and thinning conditions, are also becoming more competitive.
Text 4
The productivity and cost-competitiveness of multi-function machines are typically very sensitive to tree size. The productivity of forest tractor-mounted harvesters in late thinnings and clear cuttings varies between 15-50 m timber operating hour depending on tree size and the type of machine. The smallest harvesters mounted on light rubber-tracked vehicles may produce 4-5 m timber per operating hour under difficult conditions of early thinnings. Haulage to the road side is performed with a load-carrying forwarder, equipped with a long-reach hydraulic
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crane. Except early thinnings, typical logging operations produce pine sawlogs, spruce sawlogs, birch veneer logs, and pulpwood from each of the three tree species. The forwarder sorts different timber assortments to their own piles at the landing site. Depending on the hauling distance, terrain, site conditions, type of equipment, and the skill of the driver, the output varies generally from 8 to 15 m per operating hour. For small rubber-tracked vehicles the transport output remains significantly lower.
The most common type of off-road transport machine is a six-wheel 10-12t forwarder. Due to their better environmental properties, the number of eight-wheel forwarders is increasing. The newest forwarders are light and have a long crane reach.
Long-distance transport is done with a self-loading truck-trailer unit. To increase the load capacity, the truck's own crane is usually detached and left at the landing site after completing the loading.
The most common timber haulage combination is composed of a three-axle truck, equipped with a three-axle full-trailer and a detachable grapple loader.
Вариант 3
Text 1
Market economies are directed by prices. As the price of an item rises, sellers are encouraged to increase production, and consumers are discouraged from purchasing the item. When the price falls, the opposite is true. In this way prices send out
«signals» to buyers and sellers, keeping the economy responsive to the forces of supply and demand.
In a free market economy, prices are determined by the interaction of the forces of supply and demand. Perfectly competitive markets are those in which many buyers and sellers, with full knowledge of market conditions, buy and sell products that are identical to one another.
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Demand is the quantity of goods or services that buyers would purchase at all possible prices. Demand varies inversely with price. That is, at a higher price fewer items would be bought than at a lower one. The degree to which price changes affect demand will depend upon the elasticity of demand for a particular item. Supply, which is the quantity of goods or services that sellers would offer for sale at all possible prices at a particular time and place, varies directly with price. In other words, at a higher price, more goods and services will be offered for sale than at a lower one, and vice versa.
Text 2
A MIXED ECONOMY
A mixed economy is one in which there exists a mixture of free enterprise and government control. In some areas of a mixed economy, the government may even have a monopoly. Most of the developed countries of the world have a mixed economy. The mixture of two different economic philosophies can imply a variety of consequences for a country, some of which are seen as beneficial, while others are neutral or detrimental. Mixed economies are also known as dual economies.
In a typical mixed economy, the government may run such things as the postal service, rail lines, libraries, and in some cases, the health care service. Even in industries which are not owned or run by the government, its influence is very noticeable in the form of taxes and regulations like wage controls.
The economy of the United States is one of the more prominent examples of a mixed economy in the world. This is so because both private enterprise and government regulation have come to be integral and important to the economy as it now stands. For example, the principle of free enterprise is alive and well in the U.S. Businesses reserve the right to incorporate, and to employ and deny employment to whoever they wish, provided they do not engage in discrimination or other illegal