From the History of Dam Construction

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From the History of Dam Construction

Dams have a history just as long as such branches of civil engineering as bridge building, road construction and the laying down of canals. Not only do dams represent some of the most impressive achievements of engineers over the centuries but their vital role in supplying water to towns and cities, irrigating dry lands, providing a sources of [power and controlling floods is more than sufficient to rank dam building among the most essential aspects of man’s attempts to harness, control and improve his environment.

In antiquity dams were built as an essential part of the need to practice irrigation on which the production of food was based. It was not until the Roman came on the scene trhat the size of dams was increased and new uses were found, such as the application of dams to problems of flood control and protection. The most important contribution, however, was the reservoir dam which, to a large extent, was a result of the Roman’s concern with the water supply to cities and towns. That they were able to build so many big dams, many of which have lasted for a very long time and survived, despite eighteen centuries of use and neglect, was also a result of their evolving better methods of construction based on better materials, especially hydraulic mortar and concrete. Moreover, proper attention was paid to hydraulic problems to ensure that the water could not percolate through the dams and that when it overflowed them, spillways were provided.

The Industrial Revolution contributed much to the further development of water resources not only for water supply purposes but also for water wheels, and, later, in the 19-th century, for their logical successor - water turbines. In their mode of operation, particularly that of reaction turbines, it was a fundamentally new idea closely linked with an improved understanding of hydrodynamics. The development of electric generators refers to the major scientific discoveries in the early part of the century, and one feature of electric power was of supreme significance, namely, that it is only form of energy in a ready-to-use state which can be transmitted over long distances.

One of the greatest advantages of a water-power station is that it utilizes an energy carrier which renews itself constantly and does not exhaust energy resources. This makes its maintenance costs relatively low.

With the discovery of a generator three separate seemingly diverse branches of engineering, those concerning dams, water turbines and electric generators, came together to found a new branch of power generation utilizing hydropower resources. All the three elements have undergone changes in the height, volume and efficiency.

Model analysis, a technique for stimulating the complex behaviour of a structure, a dam, for instance, promotes a reliable forecast in designing new schemes and in the transformation and modernization of the old ones to increase their efficiencies.


Systems of Heating

Heating. In order to maintain standard room temperature, the heating apparatus must supply heat to replace the lost through the walls, floors, and ceilings, and, in addition, the heat necessary to warm the cold fresh air used for ventilation. Heat is lost by conduction through cracks around doors, windows, etc.

Systems of heating. Leaving stoves and fireplaces out of consideration, the systems ordinarily employed for heating may be classified as follows:

a) hot air

b) steam

c) hot water

Hot air systems. In a hot air system, heated air from the furnace is introduced through leaders, stacks, and registers into the room. This air is at a higher temperature than the room, and, in flowing across the ceilings and down by the walls, heat is abstracted until it is eventually cooled to the desired room temperature. Fresh warm air from the furnace then forces the air that has been cooled to room temperature out of the room through cracks, fireplaces, etc. A heat balance may therefore be written as follows: the heat given up by the entering air equals the heat lost by conduction.

The force which causes hot air to flow from furnace to room results from the difference in densities of the cold air outside and the warm air inside the furnace and pipes.

Advantages. A hot air system is cheap to install, has a low cost of maintenance, and is not hard to manage, its operating cost is little, if any, greater that of hot water or steam system of equal capacity.


Positioning Tools

From using the sun, the moon and the stars to the development of compasses and maps and in very recent times the technology of satellite GPS systems and radar, man has always needed a way to find his bearings, whether travelling on foot, at sea or in the air. Navigation is as fundamental for humans today as it was in the past, and with all the sophisticated technology now available navigation tools are not just used to stop people getting lost.

Consider the transport industry for example. A GPS tracking system on a truck can ensure that a driver takes the best route - avoiding traffic, saving time and petrol costs - but it also helps the transport company to monitor the driver and ensure that he respects the speed limits, only travels at the permitted times and rests at regular intervals for the required amount of time, respecting the law and increasing safety. It can even allow the company to find the vehicle in case of theft!

You have probably used maps on the internet or your mobile phone, and have seen how satellite images can now identify places with incredible detail, even looking into your living room from the sky above! This can be useful for planning a trip before you leave or finding a friend's house; but the technology is also used for a whole series of professional purposes: from calculating weather to urban planning and even security and warfare.

Like all forms of technology the GPS has a few disadvantages of course - it is not always 100% reliable – the suggested route may not always be the best, because some problems are not signaled or the information transmitted to the map is not completely accurate; and some people consider that GPS is an invasion of their privacy. However, this technology is obviously here to stay, and destined to improve; and, if used properly, its advantages are clearly greater than its drawbacks.

Oil Tankers

The oil tanker was developed in the late 19th century as a solution for transporting large quantities of 'black gold ' across the globe. Today, oil tankers fall into two basic categories, crude tankers and product tankers.

Crude tankers are the larger of the two. They move raw, unrefined oil from the places where it's pumped out of the earth, to the refineries where it is processed into fuel and other products. Product tankers, on the other hand, are smaller than crude tankers and move already-processed petroleum products to markets where they can be sold and used. Corporations are always seeking the most efficient way to accomplish a task in order to maximize profits. Due to their immense size, oil tankers provide an easy and inexpensive way to transport oil over long distances.

In fact, it only costs around two to four cents per gallon to transport oil using a typical tanker. Like many other influential technologies, oil tankers have helped us progress as a civilization, but they have also presented us with considerable problems. Without oil tankers, it would be impossible to travel as easily and often as we do. However, some of the worst man-made environmental disasters in history have resulted from oil tanker accidents. When oil spills into the sea it creates enormous damage to nature, which takes many years to recover. In order to prevent these accidents occurring again in the future new regulations have been introduced. For example, new oil tankers must be double-hulled, which means that there are two layers separating the oil they carry from the sea. This reduces the risk of oil spills in case the tanker has an accident, but of course it does not eliminate risk completely. Sea transportation of oil also carries other risks, including pirates, who take control of the tanker and demand money in return. The future of oil tankers is also uncertain, just as the future of the oil industry itself is. Man is looking for new ways of producing energy as oil reserves are finishing and ecological issues are becoming more important.


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