080100.62/080200.62
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Public finance is the study of the role of the government in the economy. The purview of public finance is considered to be threefold: governmental effects on (1) efficient allocation of resources, (2) distribution of income, and (3) macroeconomic stabilization.
The proper role of government provides a starting point for the analysis of public finance. In theory, under certain circumstances, private markets will allocate goods and services among individuals efficiently (in the sense that no waste occurs and that individual tastes are matching with the economy's productive abilities). If private markets were able to provide efficient outcomes and if the distribution of income were socially acceptable, then there would be little or no scope for government. In many cases, however, conditions for private market efficiency are violated. For example, if many people can enjoy the same good at the same time (non-rival, non-excludable consumption), then private markets may supply too little of that good. National defense is one example of non-rival consumption, or of a public good.
"Market failure" occurs when private markets do not allocate goods or services efficiently. The existence of market failure provides an efficiency-based rationale for collective or governmental provision of goods and services. Externalities, public goods, informational advantages, strong economies of scale, and network effects can cause market failures. Public provision via a government or a voluntary association, however, is subject to other inefficiencies, termed "government failure."
Under broad assumptions, government decisions about the efficient scope and level of activities can be efficiently separated from decisions about the design of taxation systems. In this view, public sector programs should be designed to maximize social benefits minus costs (cost-benefit analysis), and then revenues needed to pay for those expenditures should be raised through a taxation system that creates the fewest efficiency losses caused by distortion of economic activity as possible. In practice, government budgeting or public budgeting is substantially more complicated and often results in inefficient practices.
Government can pay for spending by borrowing (for example, with government bonds), although borrowing is a method of distributing tax burdens through time rather than a replacement for taxes. A deficit is the difference between government spending and revenues. The accumulation of deficits over time is the total public debt. Deficit finance allows governments to smooth tax burdens over time, and gives governments an important fiscal policy tool. Deficits can also narrow the options of successor governments.
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Public finance management
Collection of sufficient resources from the economy in an appropriate manner along with allocating and use of these resources efficiently and effectively constitute good financial management. Resource generation, resource allocation and expenditure management (resource utilization) are the essential components of a public financial management system.
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Public Finance Management (PFM) basically deals with all aspects of resource mobilization and expenditure management in government. Just as managing finances is a critical function of management in any organization, similarly public finance management is an essential part of the governance process. Public finance management includes resource mobilization, prioritization of programmes, the budgetary process, efficient management of resources and exercising controls. Rising aspirations of people are placing more demands on financial resources. At the same time, the emphasis of the citizenry is on value for money, thus making public finance management increasingly vital.
190600.62
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Two-stroke configuration
Engines based on the two-stroke cycle use two strokes (one up, one down) for every power stroke. Since there are no dedicated intake or exhaust strokes, alternative methods must be used to scavenge the cylinders. The most common method in spark-ignition two-strokes is to use the downward motion of the piston to pressurize fresh charge in the crankcase, which is then blown through the cylinder through ports in the cylinder walls.
Spark-ignition two-strokes are small and light for their power output and mechanically very simple; however, they are also generally less efficient and more polluting than their four-stroke counterparts. In terms of power per cm³, a two-stroke engine produces comparable power to an equivalent four-stroke engine. The advantage of having one power stroke for every 360 of crankshaft rotation (compared to 720 in a 4-stroke motor) is balanced by the less complete intake and exhaust and the shorter effective compression and power strokes. It may be possible for a two-stroke to produce more power than an equivalent four-stroke, over a narrow range of engine speeds, at the expense of less power at other speeds.
Small displacement, crankcase-scavenged two-stroke engines have been less fuel-efficient than other types of engines when the fuel is mixed with the air prior to scavenging allowing some of it to escape out of the exhaust port. Modern designs (Sarich and Paggio) use air-assisted fuel injection, which avoids this loss and provides more efficiency than comparably sized four-stroke engines. Fuel injection is essential for a modern two-stroke engine for it to meet stringent emission standards. The problem of total loss oil consumption, however, remains a cause of high hydrocarbon emissions.
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The largest internal combustion engines in the world are two-stroke diesels, used in some locomotives and large ships. They use forced induction (similar to super-charging, or turbo charging) to scavenge the cylinders; an example of this type of motor is the Wärtsilä-Sulzer turbocharged two-stroke diesel as used in large container ships. It is the most efficient and powerful internal combustion engine in the world with over 50% thermal efficiency.[4][5][6][7] For comparison, the most efficient small four-stroke motors are around 43% thermal efficiency (SAE 900648); size is an advantage for efficiency due to the increase in the ratio of volume to surface area.
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Common cylinder configurations include the straight or inline configuration, the more compact V configuration, and the wider but smoother flat or boxer configuration. Aircraft engines can also adopt a radial configuration which allows more effective cooling. More unusual configurations such as the H, U, X, and W have also been used.
Multiple crankshaft configurations do not necessarily need a cylinder head at all because they can instead have a piston at each end of the cylinder called an opposed piston design. Because here gas in- and outlets are positioned at opposed ends of the cylinder, one can achieve uniflow scavenging, which, as in the four-stroke engine, is efficient over a wide range of engine speeds. Also the thermal efficiency is improved because of lack of cylinder heads. This design was used in the Junkers Jumo 205 diesel aircraft engine, using two crankshafts at either end of a single bank of cylinders, and most remarkably in the Napier Deltic diesel engines. These used three crankshafts to serve three banks of double-ended cylinders arranged in an equilateral triangle with the crankshafts at the corners. It was also used in single-bank locomotive engines, and is still used for marine propulsion engines and marine auxiliary generators.
151000.62
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A harvester is a type of heavy forestry vehicle employed in cut-to-length logging operations for felling, delimbingand bucking trees. A forest harvester is typically employed together with a forwarder that hauls the logs to a roadside landing.
Forest harvesters were mainly developed in Sweden and Finland and today do practically all of the commercial felling in these countries. The first fully mobile timber "harvester", the PIKA model 75, was introduced in 1973[ by Finnish systems engineer Sakari Pinomäki and his company PIKA Forest Machines. The first single grip harvester head was introduced in the early 1980s by Swedish company SP Maskiner. Their use has become widespread throughout the rest of Northern Europe, particularly in the harvesting of plantation forests.
Before modern harvesters were developed in Finland and Sweden, two inventors from Texas developed a crude tracked unit that sheared off trees at the base up to 30 inches in diameter was developed in the US called The Mammoth Tree Shears. After shearing off the tree, the operator could use his controls to cause the tree to fall either to the right or left. Unlike a harvester, it did not delimb the tree after felling it.
Harvesters are employed effectively in level to moderately steep terrain for clearcutting areas of forest. For very steep hills or for removing individual trees, humans working with chain saws are still preferred in some countries. In northern Europe small and manoeuvrable harvesters are used for thinning operations, manual felling is typically only used in extreme conditions, where tree size exceeds the capacity of the harvester head or by small woodlot owners.
The principle aimed for in mechanised logging is "no feet on the forest floor", and the harvester and forwarder allow this to be achieved. Keeping humans inside the driving cab of the machine provides a safer and more comfortable working environment for industrial scale logging.
The leading manufacturers of harvesters are Timberjack (owned by John Deere), Valmet (owned by Komatsu) and Ponsse.
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Felling head
A typical harvester head consists of (from bottom to top, with head in vertical position)
a chain saw to cut the tree at its base, and also cut it to length. The saw is hydraulically powered, rather than using the 2-stroke engine of a portable version. It has a more robust chain, and a higher power output than any saw that can be carried by a human.
two or more curved delimbing knives which reach around the trunk to remove branches.
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two feed rollers to grasp the tree. The wheels pivot apart to allow the tree to be embraced by the harvester head, and pivot together to hug the tree tightly. The wheels are driven in rotation to force the cut tree stem through the delimbing knives.
diameter sensors to calculate the volume of timber harvested in conjunction with
a measuring wheel which measures the length of the stem as it is fed through the head.
All of this can be controlled by one operator sitting in the cab of the vehicle. A control computer can simplify mechanical movements and can keep records of the length and diameter of trees cut. Length is computed by either counting the rotations of the gripping wheels or, more commonly, using the measuring wheel. Diameter is computed from the pivot angle of the gripping wheels or delimbing knives when hugging the tree.
Harvesters are routinely available for cutting trees up to 900 mm in diameter, built on vehicles weighing up to 20 t, with a boom reaching up to 10 m radius.
250100.62
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Over the past centuries, forestry was regarded as a separate science. With the rise of ecology and environmental science, there has been a reordering in the applied sciences. In line with this view, forestry is one of three primary land-use sciences. The other two are agriculture and agroforestry. Under these headings, the fundamentals behind the management of natural forests comes by way of natural ecology. Forests or tree plantations, those whose primary purpose is the extraction of forest products, are planned and managed utilizing a mix of ecological and agroecological principles.
Today a strong body of research exists regarding the management of forest ecosystems and genetic improvement of tree species and varieties. Forestry also includes the development of better methods for the planting, protecting, thinning, controlled burning, felling, extracting, and processing of timber. One of the applications of modern forestry is reforestation, in which trees are planted and tended in a given area.
In many regions the forest industry is of major ecological, economic, and social importance. Third-party certification systems that provide independent verification of sound forest stewardship and sustainable forestry have become commonplace in many areas since the 1990s. These certification systems were developed as a response to criticism of some forestry practices, particularly deforestation in less developed regions along with concerns over resource management in the developed world. Some certification systems are criticised for primarily acting as marketing tools and lacking in their claimed independence.
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Forestry plans
Foresters develop and implement forest management plans relying on mapped resource inventories showing an area's topographical features as well as its distribution of trees (by species) and other plant cover. Plans also include landowner objectives, roads, culverts, proximity to human habitation, water features and hydrological conditions, and soils information. Forest management plans typically include recommended silvicultural treatments and a timetable for their implementation.
Forest management plans include recommendations to achieve the landowner's objectives and desired future condition for the property subject to ecological, financial, logistical (e.g. access to resources), and other constraints. On some properties, plans focus on producing quality wood products for processing or sale. Hence, tree species, quantity, and form, all central to the value of harvested products quality and quantity, tend to be important components of silvicultural plans.
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Good management plans include consideration of future conditions of the stand after any recommended harvests treatments, including future treatments (particularly in intermediate stand treatments, and plans for natural or artificial regeneration after final harvests.
The objectives of landowners and leaseholder influence plans for harvest and subsequent site treatment. In Britain, plans featuring "good forestry practice" must always consider the needs of other stakeholders such as nearby communities or rural residents living within or adjacent to woodland areas. Foresters consider tree felling and environmental legislation when developing plans. Plans instruct the sustainable harvesting and replacement of trees. They indicate whether road building or other forest engineering operations are required.
140100.62/140400.62
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The core element of a district heating system is as a minimum a heat-only boiler station. Additionally a cogeneration plant (also called combined heat and power, CHP) is often added in parallel with the boilers. Both have in common that they are typically based on combustion of primary energy carriers. The difference between the two systems is that, in a cogeneration plant, heat and electricity are generated simultaneously, whereas in heat-only boiler stations - as the name suggests - only heat is generated.
In the case of a fossil fueled cogeneration plant, the heat output is typically sized to meet half of the peak heat load but over the year will provide 90% of the heat supplied. The boiler capacity will be able to meet the entire heat demand unaided and can cover for breakdowns in the cogeneration plant. It is not economic to size the cogeneration plant alone to be able to meet the full heat load.
The combination of cogeneration and district heating is very energy efficient. A simple thermal power station can be 20-35% efficient, whereas a more advanced facility with the ability to recover waste heat can reach total energy efficiency of nearly 80%.Other heat sources for district heating systems can be geothermal heat, solar heat, surplus heat from industrial processes, and nuclear power.
Nuclear energy can be used for district heating. The principles for a conventional combination of cogeneration and district heating applies the same for nuclear as it does for a thermal power station. Russia has several cogeneration nuclear plants which together provided 11.4 PJ of district heat in 2005. Russian nuclear district heating is planned to nearly triple within a decade as new plants are built.
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There are several ways that an industrial heat pump can be used, for example:
1-As the primary base load source where a low grade source of heat, e.g. river, fjord, data centre, power station outfall, sewage treatment works outfall (all typically between 0˚C and 25˚C) are boosted up the network temperature of typically 60˚C to 90˚C. Such heat pumps, although consuming electricity, will deliver over 3x and perhaps 5x the heat output as consumed electricity.
2-As a means of recovering heat from the cooling loop of a power plant to increase either the level of flue gas heat recovery (as the district heating plant return pipe is now cooled by the heat pump) or by cooling the closed steam loop and artificially lowering the condensing pressure and thereby increasing the electricity generation efficiency.
3-As a means of cooling flue gas scrubbing working fluid (typically water) from 60˚C post injection to 20˚C pre-injection temperatures. The heat is recovered using a heat pump and sold into the network side of the facility at 80˚C.
4-In situations where the network has reached capacity, large individual load users can be decoupled from the feed pipe at around 80˚C and coupled to the return pipe at 40˚C. By adding a heat pump locally to this user, the 40˚C pipe is cooled to 20˚C (the heat being delivered into the heat pump evaporator). The output from the heat pump is then a dedicated loop for the user at 40˚C to 70˚C. Therefore the overall network capacity has changed as the total delta T of the loop has changed from 80-40˚C to 80˚C-x (x being a value lower than 40˚C).
Recent advances in technology have allowed the use of natural refrigerants such as CO2 (R744) or ammonia (R717) which also have the added benefits, depending on operating conditions, of improved heat pump efficiency.
240100.62
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Characterization of the Pulp and Paper Industry
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The pulp and paper industry converts wood (harvested by logging firms in SIC 24) or recycled fiber into pulp and primary forms of paper. Other companies in the paper and allied products industry (SIC codes 265 and 267) use the products of the pulp and paper industry to manufacture specialized products including paperboard boxes, writing paper, and sanitary paper.
II.B.1. Product Characterization The pulp and paper industry produces primary products commodity grades of wood pulp, printing and writing papers, sanitary tissue, industrial-type
papers, containerboard and boxboard using cellulose fiber from timber or purchased or recycled fibers. The two steps are pulping and paper or paperboard manufacturing.
Pulping
Pulping is the process of dissolving wood chips into individual fibers by chemical, semi-chemical, or mechanical methods. The particular pulping process used affects the strength, appearance, and intended use characteristics of the resultant paper product. Pulping is the major source of environmental impacts in the pulp and paper industry. There are more than a dozen different pulping processes in use in the U.S.; each pulping process has its own set of process inputs, outputs, and resultant environmental concerns. Table 2 provides an overview of the major pulping processes and the main products that they produce.The pulp manufacturing process is the major source of environmental concern for this industry. For example, a bleached kraft pulp mill requires 4,000-12,000 gallons of water and 14-20 million Btu of energy per ton of
pulp, of which roughly 8-10 million Btu typically are derived from biomassderived fuel from the pulping process (Pulp and Paper, 2001). Across all facilities in SIC 26, the pulp, paper, and allied products industry is the largest consumer of process water and the third largest consumer of energy (behind the chemicals and metals industries) (U.S. Department of Commerce, 2000
and U.S. Department of Energy, 2000). The high use of water and energy, as well as the chemical inputs described in Section III, lead to a variety of environmental concerns.
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