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1.较多使用被动语态。机械专业英语广泛使用被动语态。这是因为被动语态既能比较客观表达事实、避免给读者以主观臆断的印象,又能在结构上有较大的调节余地,有利于采用适当的修辞手段,扩展名词短语,扩大句子的信息量,有利于突出相关的概念、问题、事实、结论等内容[2]。例如:The combustion of themixture does not take place instanta-neously. The spark is therefore timed to occur before the pistonreaches top dead centre, otherwisemaximum pressurewould notbe reached in time. By the time the piston is at top dead centre,combustion iswell underway and the expansion of the gases isbeginning. Once combustion starts, it should be carried throughthe mixture very rapidly, and this is assisted by making theclearance space above the piston as small as possible, and bycareful design of the cylinder head. Rapid propagation of theflame through the compressed gas is also assisted by creating tur-bulence in the gas.这段文字共5个句子,共使用了5个被动语态。

2.时态使用比较单一。机械专业英语使用的时态比较单一,主要使用3种时态:一般现在时、一般过去时和现在完成时。为体现陈述事实的客观性,一般现在时在机械专业英语中使用最为普遍,主要用来介绍客观规律或事实。一般过去时次之,主要用来说明某一具体项目的发展情况,介绍已进行的实验或实验过程。现在完成时应用较少,主要用来介绍论题的发展背景、已完成的工作或取得的成果。例如:Themachine tools in aworkshop sometimes have their ownelectricmotors, or they may take the power they need from amotorwhich feeds severalmachines. The shaftswhich carry thepower from themotor to themachines need some kinds ofsupportto keep them steady. We call these supports bearings. There aredifferent types ofbearings fordifferentpurposes. We can classifythem according to where they take the load on the shaft or thethrust along the axis of the shaft. The former type is known as ajournal bearing, and the latter type as a thrustbearing.该段落共6个句子,全部采用一般现在时介绍客观事实。

(四)语篇特点

1.较多使用非言语表达方式。机械专业英语较多使用非言语表达方式,如公式、图表、数学运算式等等。这样既可省去繁多的语言表述,使文体言简意赅,又可使各个相关因素之间的关系明确化、直观化,使文体更浅显易懂,一目了然。例如,Relationship betweenFpandP1isFp=P1A1-P2A2WhenFp=Fg+Ff-FsPunch position is given byhs=t+δThe reference value of springback (δ) is expressed asδ=hs-h0通过上述公式非常简单明了地表达了各参数之间的相互数值关系。通过图1也非常简单、直观、准确地表述了一个参数随另一个参数的变化情况。

2.简洁明确,逻辑流畅。机械专业英语行文简练,重点突出,言简意赅,条理清楚,形式规范。无论是机械原理叙述、设备说明、实验介绍、方案叙述等,所有用语必须精辟简练、严谨准确、逻辑流畅。在语言特点上,不强调语言形象鲜明,活灵活现[3]。例如:Broadly speaking, two kinds of relativemotionmustbe pro-vided by amachine tool?the primarymotion and the feedmo-tion. Combination of these twomotionswill lead to a chip remov-al and the creation ofmachined surface with desired geometry.As a rule, the primarymotion absorbsmosto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。