qngma76
Joined: 05 Mar 2011
Posts: 2
Read: 0 topics
Warns: 0/5
Location: England
|
|
 Posted: Sun 9:46, 06 Mar 2011 Post subject: most devastating military conflict |
|
|
|
The most devastating military conflict in modern independent Africa has been the Second Congo War. By 2008,mlb jerseys this conflict and its aftermath had killed 5.4 million people. Since 2003 there has been an ongoing conflict in Darfur which has become a humanitarian disaster. AIDS has also been a prevalent issue in post-colonial Africa.
The first safe and successful steam power plant was introduced by Thomas Newcomen before 1712. Newcomen apparently conceived the Newcomen steam engine quite independently of Savery, but as the latter had taken out a very wide-ranging patent, Newcomen and his associates were obliged to come to an arrangement with him,cheap jerseys marketing the engine until 1733 under a joint patent.[17][18] Newcomen's engine appears to have been based onPapin's experiments carried out 30 years earlier, and employed a piston and cylinder, one end of which was open to the atmosphere above the piston. Steam just above atmospheric pressure (all that the boiler could stand) was introduced into the lower half of the cylinder beneath the piston during the gravity-induced upstroke; the steam was then condensed by a jet of cold water injected into the steam space to produce a partial vacuum;ed hardy jeans the pressure differential between the atmosphere and the vacuum on either side of the piston displaced it downwards into the cylinder, raising the opposite end of a rocking beam to which was attached a gang of gravity-actuated reciprocating force pumps housed in the mineshaft. The engine's downward power stroke raised the pump, priming it and preparing the pumping stroke. At first the phases were controlled by hand,replica rolex watches but within ten years an escapement mechanism had been devised worked by a vertical plug tree suspended from the rocking beam which rendered the engine self-acting.
A number of Newcomen engines were successfully put to use in Britain for draining hitherto unworkable deep mines, with the engine on the surface; these were large machines, requiring a lot of capital to build, and produced about 5 hp (3.7 kW). They were extremely inefficient by modern standards, but when located where coal was cheap at pit heads, opened up a great expansion in coal mining by allowing mines to go deeper. Despite their disadvantages, Newcomen engines were reliable and easy to maintain and continued to be used in the coalfields until the early decades of the 19th century. By 1729, when Newcomen died,rolex wathces, his engines had spread (first) to Hungary in 1722, Germany, Austria, andSweden. A total of 110 are known to have been built by 1733 when the joint patent expired,rolex watches replica of which 14 were abroad. In the 1770s, the engineer John Smeaton built some very large examples and introduced a number of improvements. A total of 1,454 engines had been built by 1800.
The post has been approved 0 times
|
|
Profile
Log in to check your private messages
Log in
Register
