计算机英语实用教程Unit 7.doc

司爱侠 张强华 宋德富 张美兰 编著 计算机英语实用教程电子教案Unit 7 Network【教学目的】 Learn about the English terms of Network: LAN（局域网），WAN（广域网），Band（波段），bandwidth（带宽），bridge（网桥），repeater（转发器），router（路由器），full duplex（全双工），optical fiber（光纤），packet（数据包），star network（星型网络），switch（交换机），hub（集线器），TP, “Twisted Pair”（双绞线） Improve the students ability to understand the long and difficult sentences in the text. Master the key language points and grammatical structures in the text. consolidate the technical terms and important professional phrases by doing exercises. 【教学重点难点】Important technical terms: LAN（局域网），WAN（广域网），band（波段），bandwidth（带宽），bridge（网桥），repeater（转发器），router（路由器），full duplex（全双工），optical fiber（光纤），packet（数据包），star network（星型网络），switch（交换机），hub（集线器），TP, “twisted pair”（双绞线） Difficult sentences: 1. Optical input is converted to electrical form to restore a clean signal, which drives lasers that fully restores the optical signal at the original signal strength.2. The twists are important: they give it electrical characteristics which allow some kinds of communications otherwise not possible. Review the important points of essential English forward vt. buffer vt. characterize vt.【教学步骤】Step OneRead and explain Text A to the students and ask the students to keep in mind the following professional terms:Network（网络）: a group of computers working together; the physical wire etc. connecting the computersLAN（局域网）： Local Area NetworkWAN（广域网）： Wide Area Network band（波段）：A range of frequencies between two defined limits. bandwidth（带宽）：A measure of capacity of information-carrying capacity on a communications channel. bridge（网桥）：A data communications device that connects two or more network segments and forwards packets between them.repeater（转发器）：1. Equipment that receives a low-power signal, possibly converting it from light to electrical form, amplifying it or retiming and reconstructing it for transmission. 2. An optoelectrical device used at each end and occasionally intermediate points of exceptionally long fiber optic span.router（路由器）：A network device that connects two similar networks having the same network protocol. full duplex（全双工）：The simultaneous transmission of data in both directions, used when communicating between two computers.optical fiber（光纤）：Thin filaments of glass through which light beams are transmitted.packet（数据包）：Generic term for a bundle of data, organized in a specific way for transmission. bus network（总线网络）：A type of network configuration where multiple nodes share access at the physical level. Star Network（星型网络）：The descriptive name of any network which is configured with many branches attaching to a common point.switch（交换机）：a device that turns current on and off. A switch is a network hub device creating a direct connection to the destination port.hub（集线器）：The center of a star-type network is called a hub. TP, “Twisted Pair”（双绞线）：The type of wire used by the phone company to wire telephonesStep Two Help the students to analyze the following long difficult sentences: 1. Optical input is converted to electrical form to restore a clean signal, which drives lasers that fully restore the optical signal at the original signal strength. Optical input“光输入”；is converted to“被转换为”；electrical form“电格式”；to restore a clean signal,“恢复成清晰信号”。第一个定语从句关系代词which代表electrical form；第二个定语从句关系代词that代表lasers。全句参考译文：“光输入可以转换为电格式以恢复为清晰的信号。这个信号能够驱动激光完全恢复光信号的原来的信号强度”。2. It(Twisted Pair) has two conductors, which are twisted. The twists are important: they give it electrical characteristics which allow some kinds of communications, otherwise not possible.双绞线由两根导线，它们是相绞的。相绞是重要的，这能使双绞线具有电特性，正是电特性可以进行某些通讯，不相绞则不行。Step ThreeReview the important idioms of essential English forward vt. 学生们熟悉的是forward作adv.或adj.表示方向：She leaned forward to whisper something in my ear. “她倾过来跟我咬耳朵”；forward motion/movement“向前运动”。表示未来：I always look forward, not back.“我总面向未来，不想过去”；forward planning/thinking“未来的计划/超前的思维”。表示进步：This is a big step forward for democracy. “这是向民主发展的重要一步”。作为vt.常用于send a letter/an email，尤其是继发，如从旧地址发到新地址，把收到的信再转发给别人，请看例句：Ill forward any mail to your new address. “我会把所有的信件发到你的新的地址的”。Ill forward his email to you if youre interested. “如果你有兴趣我就把他的emai转发给你”。本文在解释Bridge（网桥）时是这样说的: A data communications device that connects two or more network segments and forwards packets between them. “网桥是一种数据通讯设备，它把两个或更多的网络片断连接起来使得信息包在这些网络间可以传送”。 buffer vt. buffer作名词“缓冲器”应该是学生们熟悉的，英语解释为Part of the memory used to store data temporarily while it is waiting to be used. For example, a program might store data in a printer buffer until the printer is ready to print it. 内存中等待启用临时存放数据的部分，例如打印缓冲器里可以临时存放打印程序，直到打印机准备好打印为止。作为vt.表示“缓冲”，如本文中对bridge（网桥）的定义：It(bridge) also amplifies the carrier signal, and accepts data packets, (perhaps buffering them during periods of network congestion) and forwards them. 它也可以放大载波信号、接收数据包（或许在网络堵塞期实现缓冲）及在缓冲后继续发送数据。characterize vt. describe something by stating its main qualities汉语译成“表现的特色”。有两种用法：1. 把描写特色的名词作主语，如：Bright colours and bold strokes characterize his early paintings.“他早年美术作品的特色是颜色明亮，笔画粗壮”。2. Characterizeas 把特色描述为，认为的特色是，如：In her essay, she characterizes the whole era as a period of radical change. “在评论中，她认为整个时代充满着激进变革时期的特点”。 本文的例句属于第一种用法，翻译时要使用词性转换技巧，即把characterize动词性翻译成名词“特色”或“特点”：Enormous capacity, low-cost, low-power consumption, small space, lightweight, insensitivity to electromagnetic interference characterize this transport media(Optical Fiber) . “这种传输介质（光纤）的特点是容量大、价格低、功耗低、空间小、重量轻及对电磁干扰不敏感”。Step Four Text B 难句解析1. Technology based on thin filaments of glass or other transparent materials used as the medium for transmitting coded light pulses that represent data, image and sound.本句是对Fiber Optics（纤维光学）的解释。based on的意思是“基于”，thin filaments of glass是“细的玻璃丝”，coded light pulses“编码的光脉冲”，that represent data, image and sound是一个定语从句，修饰和限定coded light pulses。 2. A type of fiber optic cable in which there is only one mode for the light to follow, thereby minimizing dispersion (smearing in the time domain).本句是对Single-Mode Fiber（单模光纤）的解释。fiber optic cable的意思是“光纤电缆”， in w