计算机CAD相关外文翻译.doc

攀枝花学院本科毕业设计（论文） 外语文翻译 攀枝花学院本科毕业设计（论文）外文译文院 （系）： 机电工程学院 专 业： 机械设计制造及其自动化 姓 名： 贺 兵 学 号： ZJD02078 指导教师评语： 签名： 年 月 日 外语文献翻译原文：3.4.1CAD HARDWAREComputersThere are two major types of hardware used in a CAD system. Computer and input/output (I/O) devices. In the early days of CAD. Some commercial CAD systems used proprietary computers. Today, nearly all CAD software runs on a general-purpose computer.Depending on the complexity of the CAD package, it may require a mainframe computer, a minicomputer, or simply a microcomputer. In general, the more functionalities a CAD system provides, the more powerful the computer needed. Three dimensional solid modelers require much more computing than do two-dimensional drafting systems; thus, they need more powerful computers. Systems that integrate engineering analysis or simulation packages generally are more computation-intensive. A powerful computer not only speeds up the response of a CAD system, but also can support multiple users without significant performance degradation. Several other parameters and components concerning the computer also have to be considered.CAD HARDWARErandom-access memory (RAM)capacity permanent disk-storage capacity special graphics accelerator tape backups RAM is the actual physical memory (vs. virtual memory)of a computer. A small memory capacity means slow processing due to frequent swapping between the physical memory and the virtual memory on disk. Because CAD is extremely storage demanding, disk capacity is important. Small disk capacity limits the system to the storage of only a few drawings. CAD is graphics-based and requires tremendous data processing. A graphics accelerator can drastically increase the performance of the system. Another component, the hard disk, is typically the major cost of a computer system. Therefore, it is not cost-justifiable to store all drawings on line on disk. Magnetic tape is still the most economical medium to use for off-line data storage. It is necessary for a CAD system to have a tape backup subsystem.Currently, all levels of computers are used in CAD systems. Personal computers are used in low-cost,2-D drafting applications, and with the new power of these computers, hey are also being used for some 3-D solid modeling applications. Engineering workstations have been the mainstay in CAD, and are usually a single-user CAD workstation in a network. Minicomputers are used in multiuser CAD systems. Mainframes are used for large multiuser CAD systems to support real time simulation and engineering analysis. Sometimes, in a large corporation, all levels of CAD systems are implemented. All these systems are linked together through a hierarchical computer network.3.4.2 Input. Output (I/O)DevicesFigure 3.7 shows the typical I/O devices used in a CAD system. Input devices are generally used to transfer information from a human or storage medium to a computer where ”CAD functions” are carried out. A keyboard is the standard input device used to transmit alphanumeric data to the system. Function keypads are also used to make input easier. Joysticks, track balls, and mousse are also used to manipulate a cursor. They can be used to position the graphic cursor(e.g. cross hair)on a monitor and feed back the location of an object on the monitor to the computer. Using these devices allows an operator to address terminal locations to interactively in reaching an accurate position. Mouses have been used extensively with windows and pull-down menus. They are easy to use for pointing; However, using a mouse to trace a curve is not an easy task.There are three basic approaches to input an existing drawing;(1)model the object on a drawing,(2)digitize the drawing, or (3)scan the object. Digitizing is usually much easier than modeling. A digitizer is a device that translates the X-Y locations on a drawing than modeling. A digitizer is a device that translates the X-Y locations on a drawing into a digital and feeds that signal to a computer. Graphics scanners scan a drawing and convert it to a CAD-system-readable format. Some scanners have built-in character-recognition software that can convert characters on paper into ASCII codes. Another input device is a sketch pad called a graphics tablet. A graphics tablet is a special flat surface on which a user draws with a stylus. The location of the stylus is sent to the computer. The tablet is an absolute coordinate device. It is easy to implement overlay menus on the tablet and pull down menus on the screen to improve the operation. Currently. the tablet is the most popular input device used in CAD other than the keyboard.The standard output device for CAD is a monitor display. Modern monitor displays are raster-scan display monitors. Similar to a TV monitor, an electron gun(Sony Trinitron uses three guns for three basic colors)sends an electronic beam to the front of the monitor. Easy display dot is called a pixel(picture element).For color displays, each pixel is represented by three closely located dots with red, green , and blue colors. The electronic beam selects the color elements and the intensity of each color element. The resolution of the monitor is determined by the number of different colors or gray scales displayable at each pixel, usually measured in bits, A 1-bit display can turn each pixel either ON or OFF.A gray scale has at least v2 bits. A 1-bit display can turn each pixel either ON or OFF.A gray scale has at least 2 bits which allow three light intensities plus an OFF (2*2).Usually, displays are 4 bits(16 colors),8 bits(256 colors),16 bits(thousands of colors),and 24bits (millions of colors).The electronic beam sweeps the screen from the top to the bottom line by line. Because the dot is lit for only a very short period of time, the sweep must be done very quickly in order not to have a flickering image. The refresh rate is a measure of how many times the monitor is redrawn in one second.The computer does not draw directly on the monitor. Connecting the computer to the monitor is u-sually a RGB(red, green, blue)cable. Three separate signal lines are connected. On the graphics board in the computer are circuits to generate the analog signals required to drive the monitor. There is also a frame buffer that serves as memory to store the image. Each pixel on the screen has a corresponding address in the frame buffer. The data in the frame buffer are converted into the appropriate analog signal and sent to the monitor at the refresh rate. Separately, the computer writes directly to the frame buffer the image it intends to draw. The greater the display size and number of colors, the more frame buffer is needed. The frame buffer on the graphics board is made of random-access memory(RAM). The calculator lend support toes to paint the software AutoCAD to make us can be with the sketch that the astonishing speed draw the engineering sketch or machine sketch and other with accuracy to sophisticate. The calculator paints to paint the different place, one of them with handicraft the paintings with out the diagram divide a step proceed of, because of but would sometimes appear the traditional handicraft the painting hour the problem of the impossible emergence. General circumstance bottom, usage the AutoCAD proceeds painting, control the precision painting and not that difficult, but want accurate then need the certain technique out the diagram. Us-ually paint or outsing diagram to have no to need to change to measure to AutoCAD system worth make the modification with establish, take its the province worth can normal work, but have the special request, must modify the related system to change measure; Too sometimes the request of the diagram paper with make the diagrams way of doing the antinomy, and be to adopt the to make the diagram method to cant attain the request of the diagram paper, will adopt some techniqueiques to modify the related system to change to measure, and can make the calculator draw to attain the request of the diagram paper with outputs sketch.AutoCAD line type establishing of comparison At teaching of process inside would usually run into what this kind of circumstance, while establishing diagram layer, clearly established the point lin eationed, and consequently output to however investigate its reason for the solid lined, and is usually because of the line typed the establishing of comparison is not appropriate and cau-sable. Should you so establish the comparison of what kind of line type? How to use the line type the comparison in the painting?Usage AutoCAD painting, besides continuous line type( Continuous), the other line type is all from the solid line segment, blank segment, point series for or text this constituting. On-line type definition document the inside have already defined these line types the segments standard length, and show on held the act or at print the machine painting output, each length and ex-portation comparison with line type comparison direct proportion. When show or print, the painting boundary that customer that request, this hour establish is out of accordance with the painting boundary of the province difference big, on held the act show or paint outputs line type would match the engineering graphics to will pass the changes line type comparison the system the method that change the deal, enlarge or contract all line types each a small segment of length, make the sketch made meet the request. In the Auto CAD, imply the adjustment line type the comparisons order: Overall situation line type comparison factor tie department exportation ratio for line type ratio factor, used foring the control not continuous line type. The Ltscale is right to have the object validity, Celtscale the province for to new object validating, twoly changing the deal w-orth all for 1.For use the line type that Auto CAD2002 painting, big part contain three kinds of forms,( such as: Comparison that Center, Center2, Center*2, Dashed, Dashed2, Dashed*2) the first is a half, the third line type for the standard form, the second line type that comparison that the first line type is the first line type of two times, if line type the comparison establish to is not suitable for, and would then make some exportation diagrams the line( such as the point lineation, dotted line.etc.) change into a solid line.Two, line breadth the count of establishPass by what handicraft painting, its painting with outs the diagram is a synchronous proceeding of, now calculator painting, its painting with outs the diagram divide a step proceeds. Wether draw the construction engineering diagram or machine spare parts diagram, at print control that a work that exportation engineering drawing, the most is a line to print the drawing the breadth, line the type, color, seal a line breadth for, and eachly growing to line type all contain its cowgirl, in the AutoCAD painting process of the old edition, even defined the line type the width, its at see the diagram area cant also display the line type the widths differentiation.( not contain many righteousness lines the Pline)Width for color for can passing the diagram layer or set upping the line coming distinguish analysing the line.What research of current painting tries a, adopt of is this kind of method.But in the AutoCAD2002, add entity that Lweight( line type the width establish) order, provided the new function for customer, then make use of the entity characteristic to proceed the control, and establish the line breadth for the sketch, and make use of it can at hold the act to up show with print to output, control the entitys line breadth.2002 versions inside print to establish and can is divided into three part, and for printing machine belong to the sex to establish, print the style to establish respectively and the page establish.Because of the model of breadth line the space is different from diagram manifestation of space paper result, in the model space therefore the elephant vegetable show, but in the diagram paper the space is then then to print the width to proceed to show, because of but we while drawing ske tch should know at the diagram line that true width established by line breadth of model space, and is not equal with object. When the line breadth is worth to establish to0, it show with the minimum width( plain breadth of an elephant) on held the act, and the line breadth settle to other worth, then come showing with the worth specific value of plain width and true unit of elephant.Three, the sketch output the establishing of comparison When we draw sketch that comparison that comparison output the sketch with us hour use different, can make originally text in the sketch that draw word exportation comparison for marking noting waiting in the outputs sketch take placing changing, therefore at drawing the sketch before returning the beard make suring the sketch.For guaranteeing the sketch to output our want the literalness size, should when the text word establish usage following formula: The text word draws the high degree the = the text word output high degree* the sketch to output the comparison; The sketch outputs the comparison= output the diagram the length for of length( width)/ diagram.( width)draw the width of the diagram line to also should consider this point, its to settle the width same as output the width to multiply by with its comparison worth. From above practice with analyze to can see out, calculator painting and incompletelyresemble handicraft painting so synchronously paint with out diagram, therefore sometimes make with the diagram method cant attain the request of the diagram paper. Some in common use system that this demand we are deep into control the calculator to paint the theories, and can expertly control the operation method to change the deal with establish the technique, and can make the work of our painting more convenient, smooth, consumedly increase to paint the level with paint the efficiency.译文：3.4.1CAD硬件计算机两大主要类型的硬件使用于CAD系统，计算机和输入/输出设备。在CAD的早期，一些商业的CAD系统使用于专业计算机。如今，几乎全部的CAD软件都运用于普通用途的计算机。根据CAD命令的复杂性，它可能需要一台大型计算机，一台迷你型计算机，或仅一台微型计算机，大体上，CAD系统提供更好的功能性，需要更有强的计算机。三维空间建模比二维线型建模需要更好的计算机；因而，他们需要更有力的计算机。那使成整体分析的系统或一般模拟命令是更多更强的计算。一台强的计算机不仅加速CAD系统的运行，而且也能支持多个使用者，并不降低使用性能。几个其他的参数和关于计算机的成分，也不得不被考虑。 随机存取储藏器容量磁带容量专用图形加速器磁带装置随机存取储藏器容量是计算机的实际的物理内存（相对，虚拟内存）。小的存取容量导致减慢是由于磁盘上的物理内存和实际内存的频繁交换。因为，CAD是要求非常大非常多的，磁盘容量是重要的。对只有一些图画的储藏小磁盘片能力极限系统， CAD是以图形为基础的并且需要巨大的数据处理，一个图形加速器能大幅增加系统的表现。另外的一个成份 ， 硬盘, 典型地是计算机系统的主要费用。 因此,它不可置疑的储藏所有线形图形到硬盘上。 磁带仍然是为脱机的数据储藏使用的最节俭的媒体。有一卷音带后缓子系统对CAD系统是必需的。现在，所有水平的计算机在CAD系统中被用。 个人计算机被用在廉价的,二维的起草申请中 , 和由于这些计算机的新力量 , 他们也被用作在一些三维建模申请。 工程工作站在CAD中有主要的依靠, 和通常在一个网络中是一个单一使用者CAD工作站.迷你计算机在数字CAD系统中被用。主机作为大的数字CAD系统是支援仿真模拟和分析。有时，在大的公司中，所有水平的CAD系统被实现。 所有的这些系统通过局域网络被一起连接。3.4.2 输入/ 输出 (输入输出) 装置图 3.7 表演在一个CAD系统中被用的典型输入输出装置。 输入装置通常用来转移来自人或储藏媒体的数据到一部计算机 CAD功能 在哪里实行。 一个键盘是标准的输入装置，过去一直送字母与数字并用的数据到系统。 功能按键区也使输入更容易。 游戏操纵杆,追踪球，而且鼠标也用来操作光标。 他们能用来放置一个监视器上的绘画似的光标 ( 举例来说十字架头发) ，而且回馈对计算机在监视器上的目标位置。使用这些装置允许一个操作员交谈式在到达一个正确的位置方面向终端指出位置。操纵杆和追踪球在CAD系统中不被广泛运用，由于很难的找到正确的位置。鼠标被广泛地用于窗口和下拉式菜单，他们为指出是容易使用的;然而, 使用一只鼠标跟踪曲线不是一件容易的工作。有三个基本接近到输入一幅已存在的图画;(1)一幅图画上的物体模型 , 数字化图画 , 或 (3) 扫描物体。 数字化通常比模型容易。一个数字化是进入数传信号之内在一幅图画上翻译 X- Y 轴位置的装置和对一部计算机的追踪信号。 图形扫描机扫描一幅图画而且将它转换成CAD系统可读格式。 一些扫描机有内建的字符识别软件进入美国信息交换标准代码密码之内在纸上转换字符。 另外的一个输入装置是一本手抄簿叫做图形平板。 一个图形平板是一个使用者用铁笔拉出的特别的平面。铁笔的位置被派遣去计算机。板是一个 同等的装置。 实现平板上的叠菜单而且实现荧屏上的下拉式菜单改良操作是容易的。 现在，平板是在键盘之外的CAD系统中流行的输入装置标准的输出装置对CAD监视器显示。现代监视器是试映图- 扫描炫耀监视器类似一个电视监视器，一个电子枪 (Sony 单枪三束彩色映像管使用三只枪作为三基本颜色)送电子的光线给监视器的前面。 每一个炫耀点叫做一个像素 (照片元素) 为彩色显示，每个像素三点之间被接近地表现为红色的，绿色的，和蓝色的颜色。电子的光线选择彩色元素和每种彩色元素的强度。监视器的分辨率被荧屏上炫耀像素的数量所决定。（像素640*480，1024*1024）和像素点大小（24位，32位，等等）。色相和灰度的决议通过不同的色相或灰色刻度决定或开或关。一个灰色刻度至少2点允许三种强度光加号远的（2*2）。通常，闪光是4点（16位色），8点（256位色），16点（数千位色），和24点（数百万色）。电子的光线从顶端到线的底线扫除荧屏。因为被为只有真正的短时段点亮, 扫除一定被非常快地依照顺序做不要有一闪烁图像。使比率尺寸是监视器在一秒内闪烁多少次来衡量。计算机不直接的依赖监视器。通常连接计算机到监视器是 RGB(红色的，绿色的,蓝色的) 电缆。 三分开信号线被连接。 在计算机中的图形是产生类比信号的线路。 也有一个视为记忆储存图像的缓冲。 荧屏上的每个像素在构成缓冲中有一个相应地址。 数据在构成缓冲中被转换成适当的类比信号并且送给监视器在那使比率。分开的，计算机直接的写到构成缓冲它想要拉出的像像。颜色的闪耀大小和数字愈比较