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spension bridges are used for very long spans.[4](P67) The deck is made of steel or reinforced concrete. It is joined to the cables by steel suspenders. The cables are usually made of many thousands of fine steel wires. 悬桥用于很长的跨度。 桥面结构用钢材或钢筋混凝土建造。 它由钢制吊杆与钢缆连接。 钢缆通常由数千根细钢丝构成。 The crude oil is heated and passed into a distillation column.[4](57) The lighter hydrocarbons are vaporized and separated near the top of the column. The heavier hydrocarbons remain liquid and are drained off at the base of the column. In another catalytic cracking unit some heavy fractions are converted into lighter fractions. 原油被加热后送进分馏塔。 较轻的碳氢化合物汽化并在塔顶附近分离出来。 较重的碳氢化合物则保持液态并由塔的底部排出。 在另一催化裂化塔中, 一些重的分馏物又被转化 成为较轻的分馏物。 四、被动不定式 被动不定式(passive infinitive)由to be 和及物动词的过去分词构成, 在日常和科技英语中都很常见。熟悉包含被动不定式的句型, 对于阅读和理解科技英语很有帮助。从中亦可了解专业人员论述科技问题时, 习惯使用的表达方式。 下面是包含被动不定式的几组例句, 参考译文附在每组例句的后面。 ( 1) 表示必要性或某种需要, 例如: There are several factors to be considered.[4](P130) That factory has to be built by a river. All the instruments need to be sterilized. It is essential for the pressure and temperature in the manned space-cabin to be automatically regulated. 有几个因素需要考虑。 那座工厂必须建在河边。 所有的器械都必须经过消毒。 载人太空舱内的气压和温度必须能够自动调节。 ( 2) 表示意图或计划, 例如: His book about gene is to be published soon. The work is not intended to be finished today. Are these components waiting to be tested? This engine is designed to be maintained at lowcost. 他写的关于基因的书即将出版。 并没计划要在今天完成这项工作。 这些零件是在等着被检测吗? 这一发动机的设计旨在降低保养维修费用。 ( 3) 表示倾向或可能性, 例如: Sandy river banks tend to be scoured by unsteady water flow. Old houses in the valley are liable to be damaged by floods. More electric power is likely to be needed in the summer. 沙质河岸易受到不稳定水流的冲刷。 河谷中的老房子容易被洪水冲毁。 在夏季可能需要更多的电能。 ( 4) 表示原因或功能, 例如: The heat causes the reaction to be accelerated. Microscopes enable small objects to be observed. That project will allow the surplus water to be utilized. It is the automatic safety valve that permits the highpressure gas in the vessel to be released in time. 热使反应加速。 显微镜使细小物体能被观察到。 那个工程将使多余的水量得到利用。 正是自动安全阀门让容器中的高压气体能够及 时排放。 参考文献: [1] A. J. 赫伯特. 科技英语的结构[M]. 北京: 冶金工业出版社, 1980. [2] 薄冰. 薄冰实用英语语法详解[M]. 太原: 山西教育出版社, 2004. [3] A. J.Themson, A.V.Martinet.A Practical English Grammar [M].London: Oxford University Press, 1986. [4] Bob Kesten. Scientifically Speaking [M]. London: English by Radio and Television BBC, 1971. 本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。