附加内容 “AS”用法小结（1）
一、 “as”的词类属性 由于“as”在文章中出现得非常频繁，且其词类属性和词义比较多，语法作用比较复杂，不少英语学习者不能迅速而准确地断定其在某一句中的词类和词义，从而造成了理解上的困难。因此，虽然不少内容在前面的有关讲课中已讲过，但有必要在此对它的用法作一简单的归纳。
“as”在句中主要可以作下面这几种词类： 1、介词 “as”是一个演变不完全的介词（往往被称为“准介词”），它的用法比较特殊，在它后面不仅可跟名词、代词或动名词，还可跟形容词、副词以及主要起形容词作用的过去分词等（特别是当它与某些动词搭配使用时）。
(1)单独使用（科技文中不常见） 主要译成“作为”(偶尔还可译成“以；像”等)。这时，“as”短语在句中主要作状语；有时还可作表语和同位语。 As an example we take(取) two parallel(平行的) plates (板) a distance a apart(分开). The basic application(基本应用) of the Zener diode(齐纳二极管) is as a voltage reference device(电压参照器件).
As a means(方法) of communication(通信), a satellite(卫星) is the most advanced(先进的). The work(功) that is done in causing(引起) a flow of current is dissipated(消耗) as heat. Sometimes fever(发烧) is induced(诱发) on purpose (故意) as a form(方式) of treatment(治疗). A direct current(直流电) is simply(只是) given(表示) by a number of(几个) amperes(安培), as 5 amperes.
(2) 与动词连用 A、与不及物动词连用：通常译成“作为”或“起…作用” 这时“as”短语在句中作状语。在科技文中最经常与“act, behave, function, serve”等动词连用，这几个动词的词义是类同的，往往可以互换。 A wire(导线) can act as an antenna(天线). In this case, the capacitor(电容器) behaves as an open circuit(开路). The tuning circuit(调谐电路) serves as a “selector(选择器).” The variable resistor(可变电阻器) functions as a means (手段) of tone control(音调控制).
B 、与及物动词连用（最常见）：译成“作为；成”。 这时“as”短语在句中绝大多数场合作补足语。与“as”连用的及物动词有许许多多，望大家要逐个记忆。 We may define(定义) heat as the kinetic energy(动能) of molecular motion(分子的运动). The binary number system(二进制数系) uses the quantity(量) 2 as its base(基数). The notion(标记) n! is read(读) as “n factorial (阶乘).” Now Z is regarded(认为) as being purely(纯) resistive (阻性的). This was regarded as impossible in the past (过去).
In what follows(下面), the vehicle(车辆) acceleration(加速度) will be taken(取) as equal to(等于) the seismic mass(震质) acceleration. The kinetic energy(动能) of the body(物体) can also be considered(看成) as made up of (由…构成)two parts(部分). The addition table(加法表) for octal numbers(八进制数) can be expressed(表示) as in Table 15.