机械工程英语 part2 所有单元翻译

1、Part02 Unit01 Computer TechnologiesIntroduction 导言 The central and essential ingredient of CAD/CAM is the digital computer. CAD/CAM最重要的组成部分是数字计算机。Its inherent speed and storage capacity have made it possible to achieve the advances is image processing, realtime process control, and a multitude of ot

2、her important functions that are simply too complex and time-consuming to perform manually.数字计算机固有的速度及其存储能力使得CAD/CAM进行图像处理，实时控制以及其他许多重要功能若手工操作复杂又耗时能简单得进行成为可能。To understand CAD/CAM, it is important to be familiar with the concepts and technoloty of the digital computer. 想要掌握CAD/CAM，熟悉数字计算机技术及理论是非常重要的

3、。 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. 现代数字计算机是一种可以根据预先设定的程序指令进行逻辑数据运算以及数据处理功能的电子仪器。The computer itself is referred to as hardware, whereas

4、 the various programs are referred to as software.计算机本身称为硬件,而各种各样的程序都被称为软件。 There are three basic hardware components of a general-purpose digital computer:通用的数字计算机有如下三个基本组成设备：Central processing unit (CPU) 中央处理单元(CPU)Memory 记忆单元Input/output (I/O) section 输入/输出单元 The relationship of these three compo

5、nents is illustrate 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). 三个设备的相关关系如图1.1所示。中央处理单元往往被认为是由两个子单元组成：控制单元和数据逻辑单元（ALU）。The control unit coordinates the operations of all the other components. It control

6、s the input and output of information between the computer and the outside world through the I/O section. 控制单元协调其他所有组件的操作，控制单元通过I/O部分控制计算机与外部环境信息的输入与输出。Synchronizes the transference of the signals between the various sections of the computer, and command the other sections in the performance of thei

7、r functions. The arithmetic-logic unit carries out the arithmetic and logic manipulations of data . It adds ,substracts, multiplies, divides, and compares numbers according to programmed instructions.指挥其他部分执行各自的功能。数字逻辑单元控制数据的运算和逻辑操作。根据程序指令进行加，减，乘，除以及数字的比较。The memory of the computer is the storage un

8、it .The data stored in this section are arranged in the form of words which can be conveniently transferred to the ALU or I/O section for processing.计算机的记忆单元是计算机的存储单元，数据以方便传输至ALU单元或者I/O部分并进行处理的语音形式存储在这一部分。 Finally, the input/output provides the means for the computer to communicate with the external

9、 world. This communication is accomplished through peripheral equipment such as readers,printers,and process interface devices. 最后，输入/输出单元提供计算机与外部设备交互的方式。这一交互是通过周边设备如读取器、打印机和过程控制接口设备实现的。The computer may also connected to external storage units(e.g.tapes,didks,etc.) through the I/O section of the com

10、puter.计算机也可以通过计算机的I/O部分连接外部存储单元（如磁带，磁盘等）。 The software consists of the program 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. The useful of the computer's memo

11、ry 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. 软件包括存储在内部和外部存储单元的程序和指令。软件分配执行各种各样用户希望计算机去执行的功能。有用的计算机内存可以很容易改变并且因此不同的程序可以放置进内存,数字计算机可以广泛应用于各种各样不同的场合。 Regardless of the application, the computer

12、 executes the program through its ability to manipulate data and numbers in their most elementary form. The data and numbers are represented in the computer by electrical signals which can take one of two alternative states. This form of representation is called the binary system. The more familiar

13、decimal number system and a whole host of software languages can utilize the binary system to permit communication between computers and human beings. 不管应用于哪种场合，计算机总是通过计算机本身最基本的操作数据和编号形式执行程序。在计算机中数据及编号是通过在两种不同状态的电信号中选择一种状态表示的。这种形式的表现被称为二进制系统。更熟悉的十进制系统和许多软件语言可以利用二进制允许计算机和人之间的交互。Central Processing Uni

14、t(CPU) 中央控制单元 The central processing unit(CPU) regulates the operation of all system components and performs the arithmetic and logical operations on the data. To accomplish these functions,the CPU consists of two operating units:Control unitArithmetic-logic unit(ALU) 中央控制单元（CPU）的功能是控制所有系统部件的运行和对数据进

15、行数字的或是逻辑的操作。为了完成上述功能，CPU由以下两个单元组成:控制单元数字逻辑单元 The control unit coordinates the various operations specified by the program instructions. 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 th

16、e arithmetic-logic unit, It sends data to the ALU and tells the ALU what functions to perform on the data and where to store the results. 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. 控制单元

17、通过程序指令来协调大量的特种操作，这些操作包括接受输入计算机的数据，并决定何时和以何种方法来处理这些数据。控制单元能指挥数字逻辑单元的操作，他把数据发送给ALU来告诉ALU根据这些数据该运行什么功能，并且在哪里把结果存储下来。控制单元完成上述操作的能力基于其安装了一个具有储存与记忆功能的总控程序机构。 The arithmetic-logic unit performs opertaions such as addition, substractions, and comparisons. These operations are carried out on data in binary f

18、orm. 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. 数字逻辑单元运行诸如加减比较之类的操作。这些操作是根据数据以二进制的形式表现出来的。在指示了确定的条件下，逻辑部也可以用来改变命令执行的次序。此外

19、，逻辑部分还具有在算术过程中编辑或清除数据等功能。 Both the control unit and the arithmetic-logic unit perform their functions by utilizing registers. Computer registers are small memory devices that can receive, hold, and transfer data. Each register consists of binary cells to hold bits of data. The number of bits in the

20、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 microcomputer) or as many as 64(large scientific computers). 控制单元和数字逻辑单元都是得用寄存器来完成他们的功能的，计算机寄存器是一个可以接收短暂存储，转移数据的小记忆装置。每个寄存器内包含有二进制小单元以来暂存二进制数据。根据计算机能力的不同，寄存器能建立出相

21、应的字节数的字长。每个词的字节数从4(早期微型计算机)到64(大型科研计算机)不等。Computer Programming Languages 计算机程序语言 The binary number system could be used to represent any decimal number, alphabetic letter, or other common symblo.Data and instructions are communicated to the computer in the form of binary words. In executing a progra

22、m. the computer interprets the configuration of bits as an instruction to perform electronic operations such as add,subtract, load into memory, and so forth. The sequence of these binary-coded instructions defines the set of calculations and data manipulations by which the computer executes program.

23、 二进制数字系统可以用于表示任意的十进制数据，字，或者其他相类似的代表性数据并且指令是以二进制的形式与计算机进行连接。在执行一个程序时，一个指令进行电子操作,如加、减、加载内存,等等时计算机就会翻译指令的字节结构。这些二进制编码指令的序列定义了计算和数据操纵是由计算机的哪条程序执行。The binary-coded instructions that computers can understand are called machine language.Unfortunately,binary-coded instructions and data are very difficult fo

24、r human programers to read or wirte. Also, different machines use different machine languages. To facilitate the task of computer programming, higer-level languages are available which can be learned with relative ease by human beings. In all there are three levels of computer programming languages:

25、Machine languagesAssembly languagesProcedure-oriented(high-level) languages. 计算机能识别的二进制编码指令叫机器语言，不幸的是，二进制编码指令和数据，人类程序员是难以去读和写的。另外，不同的机器应用不同的程序语言，为使计算机编程任务变得简单，高级语言可供选择,可以较容易地学习的人。总共有三种不同计算机程序语言。机器语言汇编语言面象过程语言（高级语言）Machine and Assembly languages 机器与汇编语言 The language used by the computer is called mac

26、hine language. It is written in binary, with each instruction containing an operation code and an operand. The operand might be a memory address, a device address, or data. In machine language programming, storage locations are designated for the program and data, and these are used throughout the p

27、rogramming to refer to specific data or program steps. In addition, the programmer must be familiar with the specific computer system since machine language instructions are different for each computer. Programming in machine language is tedious, complicated, and time-consuming. To alleviate the dif

28、ficulties in writing programs in binary, symbolic languages have been developed which substitute an English-like mnemonics for each binary instruction. Mnemonics are easier to be remembered than binary, so they help speeding up the programming the process. A language consisting of mnemonic instructi

29、ons is called an assembly language. 计算机运用的语言叫机器语言。运用二进制进行编写。每个指令都包含有一个操作码和操作数。操作数可以是一个内存地址，一个设备地址或者是数据。在机械语言程序中，存储单元指定程序和数据，并且这种指定应用于整个程序以指向特定的数据或者程序步。此外，每个程序员必须熟悉特定的计算机系统因为每种计算机的机器语言指令是彼此不同的。机器语言编程是乏味的,复杂、而且耗费时间的。为了减轻在编写二进制程序的困难，符号语言已经开发出一种每一个英语助记符代替二进制指令。助记符比起二进制是比较容易记忆的，所以它们帮助提高程序的处理速度。包含有助词符指令的语

30、言叫做汇编语言。 Assembly languages are considered to be low-level languages. The programmer must be very knowledgeable about the computer and equipment being programmed. Low-level languages are the most efficient in terms of fast execution on the computer, but there are obvious difficulties for the program

31、mer in writing large programs for various applications using different computers. 汇编语言也被认为是低级语言，程序员必须对计算机语言及被编制设备有相当的了解。在计算机中低级语言能最有效的快速的执行。但是让程序员运用不同的计算机为各种各样的场合编写大量的程序有明显的难度。 Assembly language programs must be converted into machine language before the computer can execute them. The conversion is

32、carried out by a program called an assembler. The assembler takes the assembly language program. performs the neccessary conversions, and produces two new programs ; the machine language version and an assembly listing. The assembly listing shows mnemonic instructions and their associated machine la

33、guage equivalents.and any erros the original assembly language program may have contained. 在计算机能运行汇编语言程序之前，汇编语言程序必须转换为相应的机器语言，一种叫汇编器的程序完成这一转换。汇编器将汇编语言程序进行必要的转换，并产生两种新的程序：机器语言版本和汇编列表。汇编列表显示与机器语言相对应的助词符。并且任何原始的汇编语言程序错误都会包含在其中。High-level Language 高级语言 Assembly languages are machine oriented. High-level

34、 languages, by constrast. are procedure oriented. They are to a large extent independent of the computer on which they are used. This means that a program written on one computer can be run on a different computer without any significant modifications to the program. 汇编语言是面向机器，高级语言，相反地，是面向过程的。高级语言在计

35、算机上运用时有很大的独立性。这意味着一个程序在一台计算机上编写可在不同计算机上运行而不用对程序进行大的修改。High-level languages consist of English-like statements and traditional mathematical symbols. Each high-level statement is equivalent to many instructions in machine language.高级语言由英语式声明和传统的数字符号组成。每一个高级声明相当于机器语言中的许多指令。 The advantage of high-level

36、languages is that it is not necessary for the programmer to be familiar with the machine language. The program is written as an English-like algorithm to solve a problem. Like assembler languages, high-level languages must also be converted into machine code. This is accomplished by a special progra

37、m called a compiler. The computer takes the high-level program, and converts it into a lower-level code. such as the machine language. If there are any statement errors in the program(e.g.misspelled words), error messages are printed in a special program listing by the compiler.高级语言的优点在于程序员不必对机器语言很熟

38、悉，程序写成英语算法的形式解决相应问题。像汇编语言一样，高级语言必须转换成机器代码。这一功能的实现是通过一种特殊的叫编译器的程序完成的。计算机接收高级程序并将它转换成低级代码，如机器语言。如果在程序中有任何的声明错误（如字母的拼写错误），编译器上都会将错误信息打印在一个特殊的程序列表中。There are many different high-level languages, Some of the most commonly used of there are BASIC,COBOL,FORTRAN,APL,RPG,PL/1,and PASCAL. 有许多不同的高级语言,最常用的一些有BA

39、SIC,COBOL,FORTRAN,APL,RPG,PL/1,and PASCAL。Computer Process Interfacing 计算机程序接口 To be useful, the computer must be capable of communicating with its environment. In a data processing system, this communication is accomplished by various input/output devices such as card readers, printers, and CRT con

40、soles. In computer-aided manufactring, the environment of the computer includes not only these devices but also includes one or more manufacturing processes.Functioning as a process control system, the computer must be capable of sensing the important process variables from the operation and providi

41、ng the necessary responses to maintain effective control over the process control system. 为了使信息有用,计算机必须有与周围环境交互的能力。在一个数据程序系统中，这一交互功能是通过各种各样的输入/输出设置完成的，如读卡器，打印机，以及CRT控制台。在计算机辅助制造中，计算机周边环境不仅包括这些设备还包括一或者更多的制造程序。如工艺控制系统功能，计算机就必须具备有从操作中感应重要变量的能力，并通过工艺控制系统提供必要的响应去保持有效的控制。(1)Manufacturing process data. The

42、 data that must be communicated between the manufacturing process and the computer. These data can be clasified into three categories:Continuous analog signalsDiscrete binary dataPulse data （1）制造过程数据：制造过程与计算机之间的数据必须能够相互交流。这些数据可以定义成下列三种分类：连续模拟信号离散二进制信号脉冲信号 Continuous analog data can be represented by

43、 a variable that assumes a continuum of values over time.During the manufacturing process cycle, it remains uniterrupted, and the values it can assume are restricted to a finite range.Examples of analog variables include temperature, pressure,liquid flow rate, and velocity.Each of these phenomena ar

44、e continuous functions over time and are capable of taking on all infinite number of values in a certain range. The number of values permitted is a function of the ability of measuring instruments to distinguish between different signal levels.连续模拟的数据可以表示为一个变量,即假设连续统一的值，经过制造过程循环，信号保持不间断，并且信号值可以假设被限制

45、在一个有限的范围内。模拟信号的例子包括温度，压力，液体流速，以及速度。每一种现象都是随时间连续的函数。并且在一定范围内可取所有无数的值。允许的数值大小是一个函数计量器具区分不同信号的水平能力的大小。Discrete binary data can take on either of two possible values, such as on and off, or open and closed.Switches, motors, valves, and lights are all devies whose status at any time may be a binary funct

46、ion.Binary data are represented in electronic digital systems as typically one of two voltage levels whose values depend on the specific devices that make up the system.Typical voltage levels are 0 and +5V. 离散二进制数据可处于两种不同的值。如开和关，打开与关闭，开关，马达，阀门，以及灯这些设备的状态在任何时候都是二元函数。二进制数据都是用电数字系统表示的，通常两个电压水平的那个值依赖于特定

47、的设备组成的系统,典型的电压水平是0和+ 5V。 Pulse data consist of a train of pulsed electrical signals from devices called pulse generators.The pulse train can be used to drive devices such as stepping motors.The magnitude of each pulse is fixed; the magnitude of the pulse train is the number of pulses it contains.Sin

48、ce the number of pulses in a series can be counted over a period of time, that number can be represented as digital data. Conversely, digital data can be used to produce a pulse train of a given magnitude. 脉冲数据是由一系列脉冲发生器设备产生的脉冲电子信号组成。脉冲链可以用于驱动设备,如步进电机，每个脉冲的大小都是固定的，脉冲链的大小取决于包含的脉冲的数量。从一个周期时间内脉冲一系列的脉冲数

49、可以计算，计算的脉冲数可用数字数据进行表示。相反地，通过数字数据可以产生给定大小的脉冲链。(2)System interpretation of process data. The three categories of manufacturing process data must be capable of interacting with the computer. For monitoring the process, input data must be entered into the computer. For controlling the process, output da

50、ta must be generated by the computer and converted into signals understandable by the manufacturing process. There are six catagories of computer-process interface representing the inputs and outputs for the three types of process data. There categories are:Analog to digitalContact inputDigital to a

51、nalogContact outputPulse generators (2)系统的过程数据解释：三大类的制造过程数据必须具备与计算机交互的能力。监测的过程中，数据必须输入计算机中。控制的过程中，输出数据必须由电脑产生并转换成能被制造过程识别的信号。在此过程中，有六大类计算机过程接口描述了三大类型过程数据的输入与输出。分类如下：模拟到数字转换 接触输入端数字到模拟转换 接触输出端脉冲发生器Analog-to-digital interfacing involves transforming real-valued signals into digital representations of

52、their magnitude. A number of different steps must be accomplished to affect this conversion process. These steps involve the following hardware:模拟数字的接口包含将实信号转变成相应大小的数字形式。许多不同的步骤必须做到影响这转换过程.这些步骤包含以下硬件：1.Transducers, which convert a measurable process characteristic(flow rate, temperature, process,etc

53、.) into electrical voltage levels corresponding in magnitude to the state of the characteristic of the process measured. A thermocouple is an example of a device in this category. It converts temperature into a small voltage level. 1.传感器:传感器将测量的过程特征（如流速，温度，位移等）转换成与相应过程测量状态相符合的电压值。一个热偶在这一类接口中是一种典型的装置

54、。它将温度转换成低电压。 2.Signal conditioners, which filter random electrical noise and smooth the analog signal emanating from transducing devices.2.信号调节器。信号调节器过滤随机的电噪声并将从转换器设备中产生的模拟信号平稳，流畅。3.Multiplexers, which connect several process-monitoring devices to the analog-to-digital converter(ADC). Each process s

55、ignal is sampled at periodic intervals and passed on to the converter. 3.多路调制器：多路调制器通过几个过程监控设备与模拟到数字变换器连接（ADC）。每个过程信号在周期间隔取样并通过转换器。4.Amplifiers scale the incoming signal up or down to the range of the analog-to-digital converter being used. 4.放大器：放大器将输入的信号放大或者缩小到模拟数字变换器要使用的范围。5.The analog-to-digital

56、 converter transforms the incoming real-valued process signals into their digital equivalents.5.模拟数字变换器：模拟数字变换器将输入的真实值过程信号转换成相应的数值。6.The digital computer's I/O section /coloraccepts the digital signals from the ADC, A limit comparator is often connected between the I/O sections and the ADC to pr

57、event out-of-limit signals from distracting the CPU.6.数字计算机I/O部分：数字计算机I/O部分从ADC中接收数字信号。I/O部分与ADC之间常常由一个限制比较器连接以防止因信号越界而分散CPU的精力。The contact input interface is a set of simple contacts that can be opened and closed to indicate the status of limit switches, button positions, and other binary-type data

58、. It serves as the intermediary between discrete process data and the computer, which periodically scans the signal status and compares it with preprogrammed values.接触输入接口是一组简单的可开可关进而表示限制开关，按钮位置及其他二进制类型数据状态的触点组成。它作为中介服务于离散过程数据与计算机之间.负责周期性地扫描信号状态并将信号状态与预定程序的值进行比较。Digital transducers belong to a class of electronic measuring instruments that generate as output a series of electrical pulses of uniform magnitude. A pulse cou