机械工程英语第二版第二部分完整翻译(叶邦彦、陈统坚主编)

机械工程英语第二版第二部分翻译

Unit 1

Introduction前言

The central and essential ingredient of GAD/CAM

is the digital computer.〔1〕Its inherent speed and storage capacity have made it possible to achieve the advances in image processing, real-time process control, and a multitude of other important functions that are simply too complex and time-consuming to perform manually. To understand CAD/CAM it is important to be familiar with the concepts and technology of the digital computer

CAD/CAM的重要组成部分是数字计算机，它固有的速度以及存储能力似的它能够在图像处理，实时过程控制以及很多因太复杂太费时而人工无法完成的其他重要功能方面获得进步，要想懂得CAD/CAM，熟悉数字电脑的概念和技术是很重要的.

The modern digital computer is an electronic machine that can perform mathematical and logical calculations and data processing functions in accordance with a predetermined program of instructions. The computer itself is referred to as hardware, whereas the various programs are referred to as software.

现在数字计算机是一部能够根据预定的程序来完成数字和逻辑运算以及数据处理功能的电子设备，计算机本身称为硬件，而各种各样的程序称为软件

There are three basic hardware components of a general-purpose digital computer; 一般用途的数字计算机由三种基本硬件组成 .Central processing unit (CPU) 微处理器 .Memory存储器

.Input/output ( I/0 )section输入/输出设备

The relationship of these three components is illustrated in Fig. 1.1. The central processing unit is often considered to consist of two subsections; a control unit and an arithmetic-logic unit (ALU). 这三个组成部分的关系如图1.1所示，中央处理器通常被认为包含两部分:一个控制器和一个运算器.The control unit coordinates the operations of all the other components. 控制器控制所有其他组成部分的运输。It controls the input and output of information between the computer and the outside world through the I/O section, synchronizes the transference of signals between the various sections of the computer, and commands the other sections in the performance of their functions.它通过输入/输出端口控制电脑与外围设备之间信息的输入与输出、控制电脑各部分间信号的传输，同时也控制其他部分完成各自的功能。 The arithmetic-logic unit carries out the arithmetic and logic manipulations of data. 运算器完成数据的算术和逻辑运算。 It adds, subtracts, multiplies, divides, and compares numbers according to programmed instructions. The memory of the computer is the storage unit. 它根据编制的程序完成数的加、减、乘、除和比较。存储器完成电脑的记忆功能。The data stored in this section are arranged in the form of words which can be conveniently transferred to the ALU or I/0 section for processing.数据被转译成便于向运算器和输入/输出设备传输以进行处理的字节形式存储在该部分中Finally, the input/output provides the means for the computer

to communicate with the external world. This communication is accomplished through peripheral equipment such as readers, printers, and process interface devices. 最后，输入/输出设备提供电脑和外部世界的交流手段，这种交流通过像阅读机、打印机和出口设备等外围设备完成。 The computer may also be connected to external storage units (e. g，tapes, disks, etc) through the UO section of the computer电脑也可以通过输入/输出设备与外围存储设备（比如磁带、磁盘）链接。.

The software consists of the programs and instructions stored in memory and in external storage units. It is the software that assigns the various functions which the user desires the system to accomplish to the computer. 软件由程序和存储在内存与外存中的指令组成。软件将使用者所要求系统完成的各项功能分配给计算机。 The usefulness of the computer lies in its ability to execute the instructions quickly and accurately. 电脑的有用性在于它快速准确地执行程序的能力。 Because the contents of the computer' s memory can be easily changed, and therefore different programs can be placed into memory, the digital computer can be used for a wide variety of applications.因为电脑存储的内容你能够很容易被改变，并且不同的程序都能够被存入，所以数字电脑能够用于多种应用。

Regardless of the application, the computer executes the program through its ability to manipulate data and numbers in their most elementary form. 不考虑这些应用，电脑能自动执行程序并以最基本的形式完成数字和数据的运算。 The data and numbers are represented in the computer by electrical signals which can take one of two alternative states.数据和数字在电脑中以两种形式的电信号的一种表示。This form of representation is called the binary system. 这种表示形式叫做二进制计数法。The more familiar decimal number system and a whole host of soft-ware languages can utilize the binary system to permit communication between computers and human beings.更多与之类似的十进制计数法以及很多软件语言利用二进制计数法在电脑和人之间实现交流。

Central Processing Unit (CPU) 中央处理器

The central processing unit (CPU) regulates the operation of all system components and performs the arithmetic and logical operations on the data. 中央处理器控制所有系统组成的操作并进行数据的算术和逻辑运算。To accomplish these functions, the CPU consists of two operating units:为了完成这些功能，中央处理器包含两个结构单元：

.Control unit ·Arithmetic-logic unit (ALU) 控制器、运算器

The control unit coordinates the various operations specified by the program instructions. 控制器控制由程序制定的各种操作。These operations include receiving data which enter the computer and deciding how and when the data should be processed. The control unit directs the operation of the arithmetic-logic unit.这些操作包括接收输入电脑的数据和决定数据的处理形式以及处理时间，控制器控制运算器的操作。 It sends data to the ALU and tells the ALU what functions to perform on the data and where to store the results. 它将数据发送给运算器并告知运算器数据所要求的处理操作和结果的存储位置。The capability of the control unit to accomplish these operations is provided by a set of instructions called an

executive program which is stored in memory.控制器完成这些操作的能力是由一组存储在存储器中被称作执行程序的指令程序提供的。

The arithmetic-logic unit performs operations such as addition, subtractions, and comparisons. These operations are carried out on data in binary form. 运算器完成像加、减和比较的功能。这些功能以二进制形式对数据进行处理。 The logic section can also be used to alter the sequence in which instructions are executed when certain conditions are indicated and to perform other functions, such as editing and masking data for arithmetic operations. 当指出某些条件时逻辑器能够改变程序执行的顺序，也能够完成其他功能，例如为运算操作编辑和屏蔽数据。

Both the control unit and the arithmetic-logic unit perform their functions by utilizing registers. 控制器和运算器都是通过寄存器来完成它们的功能。Computer registers are small memory devices that can receive，hold, and transfer data. Each register consists of binary cells to hold bits of data.计算机的寄存器是能够接收、保存和传送数据的小存储设备。每个寄存器都由能够保存二进制数的二进制单元组成。 The number of bits in the register establishes the word length with which the computer is capable of handling. The number of bits per word can be as few as 4 ( early microcomputers ) or as many as 64 ( large scientific computers ).

Computer Programming Languages存储器的位数代表了电脑能够处理的字长，每个字所占位数最少到4个（早期微型计算机）最多到64个（大型科学计算机）

The binary number system could be used to represent any decimal number, alphabetic letter, or other common symbol. 二进制数能够用来表示十进制数、字母，或者其他一般符号。 Data and instructions are communicated to the computer in the form of binary words. In executing a program. the computer interprets the configuration of bits as an instruction to perform electronic operations such as add，subtract, load into memory，and so forth. 数据和程序都以二进制码得形式输入计算机，在执行某一程序时，计算机通过翻译构成指令的字来执行像加、减、保存等电子操作。The sequence of these binary-coded instructions defines the set of calculations and data manipulations by which the computer executes the program. 这些二进制编码的顺序限定了计算机执行程序的运算组和数据运算

The binary-coded instructions that computers can understand are called machine language. Unfortunately，binary-coded instructions and data are very difficult for human programmers to read or write. 这些计算机所能识别的二进制编码叫做机器语言。不幸的是，对编码人员来说由二进制编码所形成的指令和数据是很难读写的。 Also, different machines use different machine languages. 同时，不同的机器使用不同的机器语言。 To facilitate the task of computer programming, higher-level languages are available which can be learned with relative ease by human beings. In all there are three levels of computer programming languages;为了便于计算机编程，对人来说相对容易学习的高级语言出现了。计算机程序语言总共有三种：

.Machine language .Assembly language

.Procedure-oriented ( high-level) languages机器语言、汇编语言、高级语言

Computer Process Interfacing 计算机处理技术

To be useful, the computer must be capable of communicating with its environment. 计算机要想有用必须能和它自己的环境进行交流。 In a data processing system, this communication is accomplished by various input/output devices such as card readers，printers，and CRT consoles. 在数据处理系统中，这种交流是通过输入/输出设备例如读卡器、打印机、CRT控制板等完成的。 In computer-aided manufacturing, the environment of the computer includes not only these devices but also includes one or more manufacturing processes. 在计算机辅助制造中，计算机的环境不仅包括这些设备而且包括一种或多种制造工艺。Functioning as a process control system，the computer must be capable of sensing the important process variables from the operation and providing the necessary responses to maintain effective control over the process. 。作为过程控制系统，计算机必须能够感应来自操作的重要的处理变量并提供必需的回应以维持有效地处理控制。 In the following sections we examine some of the important components of a computer process control system. 下面的部分我们检查计算机过程控制系统的一些重要部分制造过程数据。

(1) Manufacturing process data. 制造过程数据。

The data that must be communicated between the manufacturing process and the computer. 制造过程数据是必须在制造过程和计算机间进行交流的。These data can be classified into three categories:这些数据可以分成3类：

.Continuous analog signals连续模拟信号 .Discrete binary data离散的二进制数据 .Pulse data脉冲数据

( 2 ) System interpretation of process data. The three categories of manufacturing process data must be capable of interacting with the computer. 制造过程数据的这三种类型必须能和计算机进行交流。 For monitoring the process，input data must be entered into the computer. 。对于监控过程而言，输入的数据必须输入计算机。 For controlling the process，output data must be generated by the computer and converted into signals understandable by the manufacturing process. 对于控制过程而言， 输出数据必须由计算机产生并转换成制造过程能理解的信号。 There are six categories of computer-process interface representing the inputs and outputs for the three types of process data. These categories are: 有六种计算机过程接口代表了过程数据三种类型的输入和输出。他们是： .Analog to digital A/D .Contact input触点输入 .Pulse counters脉冲计数器 .Digital to analog D/A .Contact output触点输出

.Pulse generators触点输出

Computer Network Structures计算机网络结构

Network introduction网络介绍

The term “ computer network \refers to the actual physical connections between computers in different areas. 计算机网络这个术语是指计算机和不同的区域之间的物理连接。 Since its first appearance in 1964，computer networks have developed through many technology phases such as Multi-computer System，Local Area Network(LAN)，Metropolitan Area Network(MAN )，Wide Area Network(WAN)and Network Computing. 自1964年第一次出现以来，计算机网络已经发展经历了许多技术阶段例如，多机系统、局域网、城域网、广域网和以太网。 Now its appearance has become one of the most significant engineering achievements ever in human history. 现在它的出现已成为在人类历史上最有重要意义的工程成果之一。 It can be used for many purposes such as intercommunication，digital online service and information share. 有很多用途例如，互相联络、数字在线服务和信息共享。 Computer network can be used in almost every case. 计算机网络几乎可用于任何事。 The utilization of computer network in mechanical engineering includes many scientific subjects such as Network Manufacturing, Virtual Manufacturing, Flexible Manufacturing System and Agile Manufacturing. 计算机网络在机械工程上的使用包括许多科学项目例如，网络制造、虚拟制造、柔性制造系统和敏捷制造。

Unit2

Numerical Control of Production Equipment

Numerical Control (NC) is a form of programmable automation in which the

processing equipment is controlled by means of numbers, letters, and other symbols. The numbers, letters, and symbols are coded in an appropriate format to define a program of instructions for a particular workpart or job. When the job changes, the program of instructions is changed. The capability to change the program is what makes NC suitable for low-and medium-volume production. It is much easier to write new programs than to make major alterations of the processing equipment. （1）数控是程序控制的自动化，在数字控制系统中，设备通过数字，字母和符号来编码，以一种合适的格式为每一个特定的零件或工件定义一个程序指令集。当工件变化时，程序也变化，改变程序的能力也就是适合中小批量生产。写一个新程序比改变大量生产设备要容易的多。 Basic Components of NC

A numerical control system consists of the following three basic components: .program of instructions .Machine control unit .Processing equipment

基本结构：数控系统由下面三部分组成：1.控制程序；2.机器控制单元；3.加工设备。

The general relationship among the three components is illustrated in Fig.2.1 The

百度搜索“77cn”或“免费范文网”即可找到本站免费阅读全部范文。收藏本站方便下次阅读，免费范文网，提供经典小说综合文库机械工程英语第二版第二部分完整翻译(叶邦彦、陈统坚主编)在线全文阅读。