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1．Iron that is used in industry almost always contains carbon in a certain proportion．
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2．If samples of copper oxide prepared in each of three ways are converted into copper，it is found that the proportions of copper and oxygen are always the same．
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3．In particular，the introduction of high－yield rice in combination with expanded irrigation and a massive increase in the use of（nitrogen）fertilizers and pesticides has significantly improved crop yields．
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4．Such internal combustion engines are more compact than earlier steam engines and can be made to start at a moment’s notice，whereas steam engines required a waiting period while water reserve warms to be boiling point．
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5．Human being has the ability to shield themselves from the calamities of nature and the calamities imposed by others．
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6．Existing apparatus may need improvements in durability，efficiency，weight，speed，or cost．
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7．Automatic control has been applied to such electric ovens as they are using now in their plant．
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8．The speed of sound increases slightly with a rise in temperature and falls with decrease in temperature．
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9．Wind farms can alter the nearby rainfall and temperature，suggesting a need for more comprehensive studies of future energy system．
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10．The study by Vautard and colleagues shows that these effects include a mix of more rain and less rain，and warming and cooling，depending on where you are around Europe．
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11．Although perhaps only 1 percent of the life that has started somewhere will develop into highly complex and intelligent patterns，so vast is the number of planets that intelligent life is bound to be a natural part of the universe．
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12．Sonar works in water at the speed of sound much in the way radar works in air at the speed of light．
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13．As a matter of fact，the cost and price of electronic computers have prevented them form other wise wider application．
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14．Substances of all degrees of electrical conductivity exist，varying from the best conductors to the best insulators．
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15．While renewable energy is generally more expensive than conventionally produced supplies，alternative power helps to reduce pollution and to conserve fossil fuels．
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The word machine has been given a wide variety of definitions，but for the purpose of this article it is a device，having a unique purpose that augments or replaces human or animal effort for the accomplishment of physical tasks．The operation of a machine may involve the transformation of chemical，thermal，electrical，or nuclear energy into mechanical energy，or vice verse，or its function may simply be to modify and transmit forces and motions．All machines have an input and output，and a transforming or modifying and transmitting device．
Machines that receive their input energy from a natural source，such as air currents，moving water，coal，petroleum，or uranium，and transform it into mechanical energy are known as prime movers．Windmills，waterwheels，turbines，steam engines，and internal－combustion engines are prime movers．In these machines the inputs vary；the outputs are usually rotating shafts capable of being used as inputs to other machines，such as electric generators，hydraulic pumps，or air compressors．All three of the latter devices may be classified as generators；their outputs of electrical，hydraulic，and pneumatic energy can be used as inputs to electric，hydraulic，or air motors．
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正常条件下，较长隧道的挖掘是从两头同时开始，两边的施工队伍缓慢地前进，逐渐靠拢，经过一段时间，有时甚至需要数年的时间，两端隧道才会相遇。这一时刻总是非常令人兴奋的。为了确保两端隧道相遇，两者中心线的测定必须非常精确。例如，挖掘一条10英里的隧道即使开始时的误差仅为100英尺偏半英寸，那么，到了5英里处，偏差就会扩大到25英尺。在此情况下，两端隧道就根本不可能相遇了。所以，刚开始要通过三角测量法建立测线系统，从隧道一端量到另一端，翻山越岭，有时还绕来绕去。要做到精准挖掘，即使是依靠最可靠的地图也不够。通过三角测量法，定了隧道两端的入口线路，而且这两端线路必须一丝不苟地保持其正确性，一直到两端相遇。
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1． 请简单介绍一下工程技术发展史及每个阶段主要的技术特征，举例说明。
2． 请举例说明工程技术英语的语言、文体等特征。
3． 请简单介绍一下英汉两种语言的主要特点，并举例说明。