毕业设计翻译

第一篇：毕业设计翻译

地点

这座办公大楼（写字楼）坐落于Crown Place的街角—Crown Place是一条步行街，它前面就是Clifton大街和Earl大街，它与伦敦城市中心的Broadgate Development毗邻。从利物浦站台只需要步行一会儿就可以到达这儿。

建筑风格陈述

这座建筑的设计是对19世纪那种为了周边保护区而特别建立的仓库建筑风格的现代重新诠释。建筑结构采用了类似于波兰特石头材质的成对柱子以及预制混凝土横梁。同时采用了细长的中号不锈钢，这种不锈钢是用在许多由砖头、石块和生铁建造的年代更久远的周边建筑物的上升结构中的。建筑物的正面则大量采用了在预制混凝土结构中加入玻璃的方法，以达到隔离噪声的效果。地面玻璃窗被缩进了，从而在给使用者更多的私人空间的同时也让自然光照能够照进周围的地下室。

电梯、楼梯和服务中心已经被用作相邻墙面的缓冲地带。楼梯塔是用和其高度一致的薄而又垂直的玻璃灯塔覆盖着的。主要的入口是由艺术家Dan Chadwick设计的，是用悬于人行道的玻璃罩蓬式样作为标记的。在四楼高度的一个巨大而突出的预制混凝土檐口使得两层楼高的玻璃制成的双重斜坡楼顶高于地面水平高度。这个建筑物的内部材料使用的是法国石灰岩、白兰地峭壁石、白色石膏、威尼斯底泥以及浅色橡木，这些材料的组合使得建筑内部犹如一个优雅的调色板。

对于规划者和自然保护工作人员来说，需要说明的是提案的建筑物的设计应该可以和Shoreditch的自然保护区融为一体。这个建筑物的规模将和Clifton街道以及Earl街道的周边建筑物相协调。建筑物的高品质设计将使得它成为这个区域里新发展的标准。

作为一座商业写字楼，9米的结构隔栏，1.5米的计划隔栏使得广大租户灵活而高效的空间使用规划成为可能。

建筑风格讨论

一个高质量的情境设计需要和计划相一致，并且取得保护区对于拆毁一座存在的建筑后重新发展此地的同意。我们针对19世纪仓库建筑物进行了延期的研究。在周边的区域内这种建筑物很常见，这些老建筑的特点就是它们的正面是以首要、次要、再次要安排布置的。而现代建筑物的正面，则是用预制的混凝土成对柱子以及那些被具有良好透光效果的巨大凸窗不时截断的横梁构成。

预制的外观并不是一个简单的覆盖系统而是一个起着承载压力的框架，这个框架支撑着楼层石板的周边。在建造时，这些预制的柱子以及边缘横梁被支撑着。在每个边缘横梁背后的起动装置闸和成对柱子背后突出的连接电缆部分被连接在 in situ层的强化闸上。这些柱子被浇铸成中间是空管道的形状，它们的长度就是楼层的高度。柱子以将强化闸放入凹入的中空管道里然后用混凝土浆填满的方式连接起来。水沟浇铸在横梁的上部，它们是用作雨水排水沟的，以防水通过圆锥形的洞口（这些洞口是圆锥形的，用来阻止叶子和散落碎片的进入）进入到底部凸窗的顶部，水之后将流到位于玻璃边缘后面的专门设计的水沟里。那些位于预制横梁前的玻璃是用来减小雨水溅落到混凝土上的机会的，因为雨水会使混凝土退色。突出的檐口在糟糕的天气里也是起到了很好的保护作用，这也就解释了为什么预制物的表面七年后仍旧看起来很干净没有污点。

这个预制的外观一直延展到四楼楼层面的高度，它是一个巨大的突出的檐口，这个檐口遮盖着两层楼高的玻璃双重斜坡屋顶。办公楼层是建在一个九平方米的隔栏上的，这样的设计提供了一个非常充足而灵活的楼层空间。

这么多年来，我们更愿意和Histons一起工作，因为他们所提供的是高质量的产品。他

们曾是唯一一个可以提供精致混凝土加工产品的预制制造商。在Histons的发展时期，Gordon Whitwell一直是它的强劲动力，Gordon Whitwell是一个能够在最不可能环境下生产漂亮的预制控制板的公司，这个公司是由一个大农场改造而来的，位置靠近Wisbech。

在设计环节，我们和Histons讨论了最后工序、外形以及控制板的尺寸问题。他们对我们许多建筑物的细节发展有影响。我们选择从白色水泥中获取白色混凝土，用压碎的石灰岩和酸性腐蚀剂混合涂在物体表面，除了已抛光成磨石子地的有雨水沟的横梁顶部。我们和工程师Whitby Bird一起，在Crown Place发展了这种可以承载压力的外观细节。在建设时期，我们参观了靠近Wisbech的Littleport的Histons工厂，在我们被派遣前（期间包括了一次伪装工事），我们检查了每个物品的质量。Histons是一个有着精湛技术的公司，我们非常信任他们工作的质量，以及他们满足我们要求的能力。如果控制板有任何损坏或是磨损标记，特殊队伍的维修人员会及时被雇佣去修理这个表面问题，直到和水泥装饰完全匹配为止。

世界贸易大厦

Minoru Yamasaki不太可能成为世界贸易大厦建筑大发展的领导人物。他不是国际上具有法人地位的三名建筑师（Gordon Bunshaft、Wallace K.Harrison、叛教之前的Edward Durell Stone）之一。他的成名是因为他的规模适度的雕塑建筑，例如他在底特律的三十层雷诺兹建筑（1958）。他有恐高症。他所传达的设计很不寻常：一个玻璃板都没有，只有由外部柱子支撑起的双子塔，而那些柱子的作用就是作为抽象派的雕塑。

就像帝国大厦取代一百英尺高的建筑一样，世界贸易大厦是一个逻辑学和工程学的奇迹。它巨大的主体很难一下子尽收眼底：两个主体、平的顶部、110层、一个1362英尺和一个1368英尺的塔一共容纳了前所未闻的一千万平方英尺的办公空间。由于受到没有柱子的楼层板以及电梯的布置影响，每层占据了整整一英亩的空间。

这个建筑物的建筑材料目录读起来像是一个战争准备的目录：43000扇窗户、60000平方英尺的玻璃、200000吨的建筑钢材（比从Staten Island到Brooklyn的Verrazano Narrows Bridge的用量还多）、6英亩的大理石、40000个门把手、200个电梯、1200个厕所。Yamasaki是如此习惯于小规模的任务，当他获得这笔28000万美元的佣金时，他以为是打印错误，应该是2800万美元。

建筑地点是个问题，因为它是一条开垦的河流，基岩有70英尺深。工程师John Skilling和Leslie Robertson采用了一种独特的意大利技术，这个叫做用水泥建造有最坚实基础的世界最高建筑。当泥土和岩石被移走的时候，留下的是被水泥填满的坑、水和可吸收粘土的混合物，以便保持开凿墙面的牢固。具有强化功能的混凝土块被放在了水泥的下面，直到混凝土块触及基岩，并且涌出水泥才行。这个500平方英尺的地基在加固后被人们熟知为“浴盆”。这个工程功绩也同样引人瞩目，因为新挖掘的去新泽西的隧道可以尽收眼底，比基岩高五层楼的高度，一直到地基建成。

世界贸易大厦和许多同时代的玻璃盒状建筑物不同，因为它是由外部钢架而不是内部钢架支撑的。它的结构实质是一个严密的空的盒子结构，伴随着可以承受压力的钢材平台以及延伸到中心服务区的楼层通道。电梯被空中厅堂以相同的方式分散开来，而那些空中厅堂都配有高速的到达44层和78层的电梯。

这个设计的最特殊的方面在于窗户只占了建筑物表面的30%而不是所谓的外观全是玻璃的国际风格。这些窗户只有18英寸宽，被安装在间隔18英尺的柱子中间。窗户外套着铝合金，铝合金突出在玻璃窗户表面的12英寸外。这个空间间隔和Yamasaki恐高有关，从而带来了建筑结构和设计方面的考虑。很明显，除非地面到天花板窗户的宽度比他的肩膀窄，否则他就会感到不舒服。Yamasaki是这样描述他早期的雷诺兹建筑的，这些相对窄的窗户可以提供给我们广大的河流以及城市的全景，给我们一种安全感，缓解许多人在高建筑物上的恐高症。

对于这个建筑物的主要批评是它完全忽视了曼哈顿那以天空为背景的轮廓线。但是Yamasaki只接受了部分佣金，因为他那封寄给设计委员会的感谢信。信中写到：“在我看来，这不应该成为融入低空曼哈顿景色的全部形式。”他写到：“但是它应该是独特的，有其自身的亮点，为大多数地区的人们多接受的。你任务中的机会在于需要发现一种可以为大多数人们所接受的方式去规划它，这样它才会受到欢迎，让人感到友好以及人性化。”尽管没有人可以使用受欢迎、友好、人性化去描述这个结果，但是这个与众不同的漂亮的意大利哥特式尖顶窗户是对塔进行人性化以及St.Mark钟塔式样的一种尝试。

尽管是在忽视城市环境下建造的，这两座塔作为抽象派的雕塑却相应成趣。采用了Mies在芝加哥的名为Lake Shore Drive公寓的原型，Yamasaki将两个塔分开建造，这样观望者就能时刻清楚它们的空间关系了。一个建在突出的位置，另一个则以次要的、被繁荣扭曲的形式建在其后。这样观看者就能始终直接面对其正面角度的景象了。

Yamasaki之所以选用定制的铝合金外表是因为比起标准的铝合金，定制的铝合金的风格更加柔和些，可以作为曼哈顿低空全景的一个缩影。倾斜的拐角流露出和以铬镍合金竖框为构造的帝国大厦一样的感受，那就是无限的机会感。在日落的时候，透明的玻璃罩成为了雕塑的空间容器。

第二篇：毕业设计_英语论文翻译

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毕业设计（论文）报告纸

LATHES

The basic machines that are designed primarily to do turning, facing and boring are called lathes.Very little turning is done on other types of machine tools, and nine can do it with equal facility.Because lathe can do boring, facing, drilling, and reaming in addition to turning, their versatility permits several operations to be performed with a single setup of the workpiece.This accounts for the fact that lathes of various types are more widely used in manufacturing than any other machine tool.Lathes in various forms have existed for more than two thousand years.Modem lathes date from about 1797, when Henry Maudsley developed one with a leadscrew.It provided controlled, mechanical feed of the tool.This ingenious Englishman also developed a change-gear system that could connect the motions of the spindle and leadscrew and thus enable threads to be cut.Lathe Construction.The essential components of a lathe are depicted in the block diagram of Fig.15-1.These are the bed, headstock assembly, tailstock assembly, carriage assembly, quick-change gear box, and the leadscrew and feed rod.The bed is the backbone of a lathe.It is usually made of well-normalized or aged gray or nodular cast iron and provides a heavy, rigid frame on which all the other basic components are mounted.Two sets of parallel, longitudinal ways, inner and outer, are contained on the bed, usually on the upper side.Some makers use an inverted V-shape for all four ways, whereas others utilize one inverted V and one flat way in one or both sets.Because several other components are mounted and/or move on the ways they must be made with precision to assure accuracy of alignment.Similarly, proper precaution should be taken in operating a lathe to assure that the ways are not damaged.Any inaccuracy in them usually means that the accuracy of the entire lathe is destroyed.The ways on most modern lathes are surface hardened to offer greater resistance to wear and abrasion.The headstock is mounted in a fixed position on the inner ways at one end of the lathe bed.It provides a powered means of rotating the work at various speeds.It consists, essentially, of a hollow spindle, mounted in accurate bearings, and a set of transmission gears---similar to a truck transmission---through which the spindle can be rotated at a number of speeds.Most lathes provide from eight to eighteen speeds, usually in a geometric ratio, and on modern lathes all the

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毕业设计（论文）报告纸

speeds can be obtained merely by moving from two to four levers.An increasing trend is to provide a continuously variable speed range through electrical or mechanical drives.Because the accuracy of a lathe is greatly dependent on the spindle, it is of heavy construction and mounted in heavy bearings, usually preloaded tapered roller or ball types.A longitudinal hole extends through the spindle so that long bar stock can be fed through it.The size of this hole is an important size dimension of a lathe because it determines the maximum size of bar stock that can be machined when the material must be fed through the spindle.The inner end of the spindle protrudes from the gear box and contains a means for mounting various types of chucks, face plates, and dog plates on it.Whereas small lathes often employ a threaded section to which the chucks are screwed, most large lathes utilize either cam-lock or key-drive taper noses.These provide a large-diameter taper that assures the accurate alignment of the chuck, and a mechanism that permits the chuck or face plate to be locked or unlocked in position without the necessity of having to rotate these heavy attachments.Power is supplied to the spindle by means of an electric motor through a V-belt or silent-chain drive.Most modern lathes have motors of from 5 to 15 horsepower to provide adequate power for carbide and ceramic tools at their high cutting speeds.The tailstock assembly consists, essentially, of three parts.A lower casting fits on the inner ways of the bed and can slide longitudinally thereon, with a means for clamping the entire assembly in any desired location.An upper casting fits on the lower one and can be moved transversely upon it on some type of keyed ways.This transverse motion permits aligning the tailstock and headstock spindles and provides a method of turning tapers.The third major component of the assembly is the tailstock quill.This is a hollow steel cylinder, usually about 2 to 3 inches in diameter, that can be moved several inches longitudinally in and out of the upper casting by means of a handwheel and screw.The open end of the quill hole terminates in a Morse taper in which a lathe center, or various tools such as drills, can be held.A graduated scale, several inches in length, usually is engraved on the outside of the quill to aid in controlling its motion in and out of the upper casting.A locking device permits clamping the quill in any desired position.The carriage assembly provides the means for mounting and moving cutting tools.The

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毕业设计（论文）报告纸

carriage is a relatively flat H-shaped casting that rests and moves on the outer set of ways on the bed.The transverse bar of the carriage contains ways on which the cross slide is mounted and can be moved by means of a feed screw that is controlled by a small handwheel and a graduated dial.Through the cross slide a means is provided for moving the lathe tool in the direction normal to the axis of rotation of the work.On most lathes the tool post actually is mounted on a compound rest.This consists of a base, which is mounted on the cross slide so that it can be pivoted about a vertical axis, and an upper casting.The upper casting is mounted on ways on this base so that it can be moved back and forth and controlled by means of a short lead screw operated by a handwheel and a calibrated dial.Manual and powered motion for the carriage, and powered motion for the cross slide, is provided by mechanisms within the apron, attached to the front of the carriage.Manual movement of the carriage along the bed is effected by turning a handwheel on the front of the apron, which is geared to a pinion on the back side.This pinion engages a rack that is attached beneath the upper front edge of the bed in an inverted position.To impart powered movement to the carriage and cross slide, a rotating feed rod is provided.The feed rod, which contains a keyway throughout most of its length, passes through the two reversing bevel pinions and is keyed to them.Either pinion can be brought into mesh with a mating bevel gear by means of the reversing lever on the front of the apron and thus provide “forward” or “reverse” power to the carriage.Suitable clutches connect either the rack pinion or the cross-slide screw to provide longitudinal motion of the carriage or transverse motion of cross slide.For cutting threads, a second means of longitudinal drive is provided by a lead screw.Whereas motion of the carriage when driven by the feed-rod mechanism takes place through a friction clutch in which slippage is possible, motion through the lead screw is by a direct, mechanical connection between the apron and the lead screw.This is achieved by a split nut.By means of a clamping lever on the front of the apron, the split nut can be closed around the lead screw.With the split nut closed, the carriage is moved along the lead screw by direct drive without possibility of slippage.共 14 页 第 3 页

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毕业设计（论文）报告纸

Modern lathes have a quick-change gear box.The input end of this gear box is driven from the lathe spindle by means of suitable gearing.The output end of the gear box is connected to the feed rod and lead screw.Thus, through this gear train, leading from the spindle to the quick-change gear box, thence to the lead screw and feed rod, and then to the carriage, the cutting tool can be made to move a specific distance, either longitudinally or transversely, for each revolution of the spindle.A typical lathe provides, through the feed rod, forty-eight feeds ranging from 0.002 inch to 0.118 inch per revolution of the spindle, and, through the lead screw, leads for cutting forty-eight different threads from 1.5 to 92 per inch.On some older and some cheaper lathes, one or two gears in the gear train between the spindle and the change gear box must be changed in order to obtain a full range of threads and feeds.CUTTING TOOL

Shape of cutting tools, particularly the angles, and tool material are very important factors.The purpose of this unit is to introduce the cutting tool geometry and tool materials.Cutting Tool Geometry

Angles determine greatly not only tool life but finish quality as well.General principles upon which cutting tool angles are based do not depend on the particular tool.Basically, grinding wheel are being designed.Since, however, the lathe(turning)tool, depicted in Fig.14-1, might be easiest to visualize, its geometry is discussed.Tool features have been identified by many names.The technical literature is full of confusing terminology.Thus in the attempt to clear up existing disorganized conceptions and nomenclature, the American Society of Mechanical Engineers published ASA Standard B5-22-1950.what follows is based on it.A single-point tool is a cutting tool having one face and one continuous cutting edge.Tool angles identified in Fig.14-2 are as follows:(1)Back-rake angle,(2)Side-rake angle,(3)End-relief angle(4)End-relief angle(5)Side-relief angle(6)End-cutting-edge angle,(7)Side-cutting-edge angle,(8)Nose angle,(9)Nose radius.Tool angle 1, on front view, is the back-rake angle.It is the angle between the tool face and a line parallel to the base of the shank in a longitudinal plane perpendicular to the tool base.Then this angle is downward from front to rear of the cutting edge, the rake id positive;when upward

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毕业设计（论文）报告纸

from front to back, the rake is negative.This angle is most significant in the machining process, because it directly affects the cutting force, finish, and tool life.The side-rake angle, numbered 2, measures the slope of the face in a cross plane perpendicular to the tool base.It, also, is an important angle, because it directs chip flow to the side of the tool post and permits the tool to feed more easily into the work.The end-relief angle is measured between a line perpendicular to the base and the end flank immediately below the end cutting edge;it is numbered 3 in the figure.It provides clearance between work and tool so that its cut surface can flow by with minimum rubbing against the tool.To save time, a portion of the end flank of the tool may sometimes be left unground, having been previously forged to size.In such case, this end-clearance angle, numbered 4, measured to the end flank surface below the ground portion, would be larger than the relief angle.Often the end cutting edge is oblique to the flank.The relief angle is then best measured in a plane normal to the end cutting edge perpendicular to the base of the tool.This clearance permits the tool to advance more smoothly into the work.The side-relief angle, indicated as 5, is measured between the side flank, just below the cutting edge, and a line through the cutting edge perpendicular to the base of the tool.This clearance permits the tool to advance more smoothly into the work.Angle 6 is the end-cutting-edge angle measured between the end cutting edge and a line perpendicular to the side of the tool shank.This angle prevents rubbing of the cut surface and permits longer tool life.The side-cutting-edge angle, numbered 7, is the angle between the side cutting edge and the side of the tool shank.The true length of cut is along this edge.Thus the angle determines the distribution of the cutting force.The greater the angle, the longer the tool life;but the possibility of chatter increases.A compromise must, as usual, be reached.The nose angle, number 8, is the angle between the two component cutting edges.If the corner is rounded off, the arc size is defined by the nose radius 9.the radius size influences finish and chatter.Cutting Tool Materials

A large number of cutting tool materials have been developed to meet the demands of high

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metal-removal rates.The most important of these materials and their influence on cutter design, are described below.High Carbon Steel.Historically, high carbon steel was the earliest cutting material used industrially, but it has now been almost entirely superseded since it starts to temper at about 220℃ and this irreversible softening process continues as temperature increases.Cutting speeds with carbon steel tools are therefore limited to about 0.15m/s(30ft/min)when cutting mild steel, and even at these speeds a copious supply of coolant is required.High-speed Steel.To overcome the low cutting speed restriction imposed by plain carbon steels, a range of alloy steels, known as high-speed steels, began to be introduced during the early years of this century.The chemical composition of these steels varies greatly, but they basically contain about 0.7% carbon and 4% chromium, with addition of tungsten, vanadium, molybdenum and cobalt in varying percentages.They maintain their hardness at temperatures up to about 600℃, but soften rapidly at cutting speeds in excess of 1.8m/s(350ft/min), and many cannot successfully cut mild steel faster than 0.75m/s(150ft/min).Sintered Carbides.Carbide cutting tools, which were developed in Germany in the late 1920s, usually consist of tungsten carbide or mixtures of tungsten carbide and titanium or tantalum carbide in powder form, sintered in a matrix of cobalt or nickel.Because of the comparatively high cost of this tool material and its low rupture strength, it is normally produced in the form of tips which are either brazed to a steel shank or mechanically clamped in a specially designed holder.Mechanically clamped tool tips are frequently made as throwaway inserts.When all the cutting edges have been used the inserts are discarded, ad regrinding would cost more than a new tip.The high hardness of carbide tools at elevated temperatures enables them to be used at much faster cutting speeds than high-speed steel(of 3-4m/s（600-800ft/min）when cutting mild steel).They are manufactured in several grades, enabling them to be used for most machining applications.Their earlier brittleness has been largely overcome by the introduction of tougher grades, which are frequently used for interrupted cuts including many arduous face-milling operations.Recently, improvements have been claimed by using tungsten carbide tools coated with

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毕业设计（论文）报告纸

titanium carbide or titanium nitride(about 0.0005mm coating thickness).These tools are more resistant to wear than conventional tungsten carbide tools, and the reduction in interface friction using titanium nitride results in a reduction in cutting forces and in tool temperatures.Hence, higher metal removal rates are possible without detriment to tool life or alternatively longer tool lives could be achieved at unchanged metal removal rates.The uses of other forms of coating with aluminum oxide and polycrystalline cubic boron nitride are still in an experimental stage, but it is likely that they will have important applications when machining cast iron, hardened steels and high melting point alloys.Ceramics.The so-called ceramic group of cutting tools represents the most recent development in cutting tool materials.They consist mainly of sintered oxides, usually aluminum oxide, and are almost invariably in the form of clamped tips.Because of the comparative cheapness of ceramic tips and the difficulty of grinding them without causing thermal cracking, they are made as throw-away inserts.Ceramic tools are a post-war introduction and are mot yet in general factory use.Their most likely application is in cutting metal at very high speeds, beyond the limits possible with carbide tools.Cramics resist the formation of a built-up edge and in consequence produce good surface finishes.Since the present generation of machine tools is designed with only sufficient power to exploit carbide tooling, it is likely that, for the time being, ceramics will be restricted to high-speed finish machining where is sufficient power available for the light cuts taken.The extreme brittleness of ceramic tools has largely limited their use to continuous cuts, although their use in milling is now possible.As they are poorer conductors of heat than carbides, temperatures at the rake face are higher than in carbide tools, although the friction force is usually lower.To strengthen the cutting edge, and consequently improve the life of the ceramic tool, a small chamfer or radius is often stoned on the cutting edge, although this increases the power consumption.Diamonds.For producing very fine finishes of 0.05-0.08um（2-3um)on non-ferrous metals such as copper and aluminum, diamond tools are often used.The diamond is brazed to a steel shank.Diamond turning and boring are essentially finishing operations, as the forces imposed by any but the smallest cuts cause the diamond to fracture or be torn from its mounting.Under

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suitable conditions diamonds have exceptionally long cutting lives.Synthetic polycrystalline diamonds are now available as mechanically clamped cutting tips.Due to their high cost they have very limited applications, but are sometimes used for machining abrasive aluminum-silicon alloys, fused silica and reinforced plastics.The random orientation of their crystals gives them improved impact resistance, making them suitable for interrupted cutting.共 14 页 第 8 页

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车床

用于车外圆、端面和镗孔等加工的机床称作车床。车削很少在其他种类的机床上进行，因为其他机床都不能像车床那样方便地进行车削加工。由于车床除了用于车外圆还能用于镗孔、车端面、钻孔和铰孔，车床的多功能性可以是共建在一次定位安装中完成多种加工。这种是在生产中普遍使用的各种车床比其他种类的机床都要多的原因。

两千多年前就已经有了车床。现代车床可以追溯到大约1797年，那时亨利·莫德斯利发明了一种具有丝杠的车床。这种车床可以控制工具的机械进给。这位聪明的英国人还发明了一种把主轴和丝杠相连的变速装置，这样就可以切削螺纹。

图15-1中标出了车床的主要部件：床身、主轴箱组件、尾架组件、拖板组件、变速齿轮箱、丝杠和光杠。

床身是车床的基础件。它通常是由经过充分正火或时效处理的灰铸铁或者球墨铸铁制成，它是一个坚固的刚性框架，所有其他主要部件都安装在床身上。通常在床身上那个面有内外另组平行的导轨。一些制造厂生产的四个条导轨都采用倒“V”形，而另一些制造厂则将倒“V”形导轨和平面导轨相结合。由于其他的部件要安置在导轨上并（或）在导轨上移动，导轨要经过精密加工，以保证其装配精度。同样地，在操作中应该小心，以避免损伤导轨。导轨上的任何误差，常常会使整个机床的精度遭到破坏。大多数现代车床的导轨要进行变面淬火处理，以减少磨损和擦伤，具有更大的耐磨性。

主轴箱安装在车身一端内导轨的固定位置上。它提供动力，使工件在各种速度下旋转。它基本上有一个安装在精密轴承中的空心主轴和一系列变速齿轮——类似于卡车变速箱所组成，通过变速齿轮，主轴可以在许多种转速下旋转。大多数车床有8～18种转速，一般按等比级数排列。在现代车床上只需扳动2～4个手柄，就能得到全部档位的转速。目前发展的趋势是通过电气的或机械的装置进行无极变速。

由于车床的精度在很大程度上取决于主轴，因此主轴的结构尺寸较大，通常安装在紧密配合的重型圆锥滚子轴承或球轴承中。主轴中有一个贯穿全长的通孔，长棒料可以通过该孔送料。主轴孔的大小是车床的一个重要尺寸，因为当工件必须通过主轴孔供料时，它确定了能够加工棒料毛坯的最大外径尺寸。

主轴的内端从主轴箱中凸出，其上可以安装多种卡盘、花盘和挡块。而小型的车

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床常有螺纹截面供安装卡盘之用。很多大车床使用偏心夹或键动圆锥轴头。这些附件组成了一个大直径的圆锥体，以保证对卡盘进行精确地装配，并且不用旋转这些笨重的附件就可以锁定或松开卡盘或花盘。

主轴由电动机经V带或无声链装置提供动力。大多数现代车床都装置有5～15马力的电动机，为硬质合金和金属陶瓷合金刀具提供足够的动力，进行高速切削。

尾座组件主要由三部分组成。底座与床身的内侧导轨配合，并可以子导轨上做纵向移动，底座上有一个可以使整个尾座组件加紧在任意位置上的装置。尾座安装在底座上，可以沿键槽在底座上横向移动，使尾座与主轴箱中的主轴对中并为切削圆锥体提供方便。尾座组件的第三部分是尾座套筒，它是一个直径通常在2～3英寸之间的钢制空心圆柱轴。通过手轮和螺杆，尾座套筒可以在尾座体中纵向移入和移出几英寸。活动套筒的开口一端具有莫氏锥度，可以用于安装顶尖或诸如钻头之类的各种刀具。通常在活动套筒的外表面刻有几英寸长的刻度，以控制尾座的前后移动。锁定装置可以使套筒在所需的位置上夹紧。

拖板组件用于安装和移动切削工具。拖板是一个相对平滑的H形铸件，安装在床身外侧导轨上，并可以在上面移动。大拖板上有横向导轨，使横向拖板可以安装在上面，并通过丝杠使其运动，丝杠由一个小手柄和刻度盘控制。横拖板可以带动刀具垂直于工件的旋转轴线切削。

大多数车床的刀架安装在复式刀座上，刀座上有底座，底座安装在横拖板上，可绕垂直轴和上刀架转动。上刀架安装在底座上，可用手轮和刻度盘控制一个短丝杠使其前后移动。

溜板箱装在大拖板前面，通过溜板箱内的机械装置可以手动和动力驱动大拖板以及动力驱动横拖板。通过转动溜板箱前的手轮，可以手动操作拖板沿床身移动。手轮的另一端与溜板箱背面的小齿轮连接，小齿轮与齿条啮合，齿条倒装在床身前上边缘的下面。

利用光杆可以将动力传递给大拖板和横拖板。光杆上有一个几乎贯穿于整个光杠的键槽，光杠通过两个转向相反并用键连接的锥齿轮传递动力。通过溜板箱前的换向手柄可使啮合齿轮与其中的一个锥齿轮啮合，为大拖板提供“向前”或“向后”的动力。适当的离合器或者齿条小齿轮连接或者与横拖板的螺杆连接，是拖板纵向移动或使横拖板横向移动。

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对于螺纹加工，丝杠提供了第二种纵向移动的方法。光杠通过摩擦离合器驱动拖板移动，离合器可能会产生打滑现象。而丝杠产生的运动是通过滑板箱与丝杠之间的直接机械连接来实现的，对于螺母可以实现这种连接。通过溜板箱前面的夹紧手柄可以使对开螺母紧紧包合丝杠。当对开螺母闭合时，可以沿丝杠直接驱动拖板，而不会出现打滑的可能性。

现代车床有一个变速齿轮箱，齿轮箱的输入端有车床主轴通过合适的齿轮传动来驱动。齿轮箱的输出端与光杠和丝杠连接。主轴就是这样通过齿轮传动链驱动变速齿轮箱，在带动丝杠和光杠，然后带动拖板，刀具就可以按主轴的转数纵向地或横向地精确移动。一台典型的车床的主轴每旋转一圈，通过光杠可以获得从0.002到0.118英寸尺寸范围内的48种进给量；而使用丝杠可以车削从1.5到92牙/英寸范围内的48种不同螺纹。一些老式的或价廉的车床为了能够得到所有的进给量和加工出多有螺纹，必须更换主轴和变速箱之间的齿轮系中的一个或两个齿轮。

金属切削刀具

刀具的形状（特别是其角度）和材料是刀具的两个非常重要的因素。本文向大家介绍刀具的几何参数和刀具材料。

刀具几何参数

刀具的角度不仅在很大程度决定了刀具的寿命，而且也决定加工的表面质量。刀具角度设计的一般性原则不因某种特殊刀具而变。车刀、铣刀、钻头甚至是砂轮的设计，所要考虑的因素基本相同。图14.1所示的车刀外形易于观察，我们即以此为例来讨论刀具的几何参数。

刀具特征参数名目繁多，技术文献中术语使用也很混乱。为了澄清已有的混乱的概念和术语，美国机械工程师协会颁布了ASA标准B5-22—1950，本文的术语即以此为依据。

单尖刀具是指只有一个前刀面和一条连续切削刃的刀具。图14-2所示各个角度定义如下：

主视图中的角度1为背前角，它是在垂直于刀具基面的纵向剖面内的平行于刀柄的一条直线与刀面之间的夹角。如该角后倾，则为正角，否则为负角。背前角对加工过程影响很大，它直接影响刀具的切削力、表面光洁度以及刀具耐用度。

角度2为侧前角，它是刀具前刀面在垂直于刀具基面的横向剖面内的倾斜角。侧

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前角也是一个重要的几何角度，它能把切屑引向刀架的一侧，并能使进给更加容易。

端后角是刀具基面的垂线与紧靠端切削刃下的断后刀面之间的夹角，即图中角度3。它确保工件和刀具之间有间隙使得切屑经过刀具时摩擦最小。为了节省磨刀时间，刀具段后刀面的一部分有时可以直接锻造成形，而不需要进行磨削。在这种强况下，从断后刀面刃磨部位下量出的角度（角度4）比端后角大。

通常端切削刃与端后刀面是斜交的，因此，端后角最好是在于端切削刃相垂直的平面内进行测量。后角也可用刀具的侧面和端面的视图来表示。

角度5表示侧后角，它是端切削刃下面的侧后刀面与通过切削刃并垂直于刀具基面的直线之间的夹角。侧后角能使刀具更平稳的切入工件。

角度6为端切削刃角，它是端切削刃和垂直于刀具柄侧面的直线之间的夹角。该角可减少刀具和已加工表面之间的摩擦，延长刀具的使用寿命。

角度7为侧切削刃角，它是测切削刃和刀柄侧面之间的夹角。由于刀具切削长度是沿着此切削刃的，因此，侧切削刃角决定了切削力的分布。该角度越大，刀具寿命越长，但颤振的可能性也随之增加。设计时，这两方面的因素都要兼顾。

角度8为刀尖角，它是两条切削刃之间的夹角。刀尖采用圆弧过渡时，圆弧的尺寸可用弧半径9来表示。刀尖圆弧半径的尺寸对表面光洁度及颤振有影响。

刀具材料

已有许多刀具材料能满足高金属切削率的要求。下面讨论最重要的几种材料和它们对刀具设计的影响。

1.高碳钢：才刀具历史上，高碳钢是最早用于工业上的刀具材料，但目前已几乎全部被废弃不用了，因为它在220°C左右开始回火，而且这种软化过程随着温度的升高而继续。因此，在切削低碳钢时，高碳钢刀具的切削速度限于大约0.15mm/s(30ft/min)，即使在这种速度时也要连续供应切削液。

2.高速钢：为克服普通碳素钢切削速度较低的特点，本世纪初，几种称为高速钢的合金钢开始用于金属切削。这些钢的化学成分差别很大，但基本上都含有大约0.7%碳和4%铬，另外还有比例不一样的钨、钒、钼和鈷。它们在高达600°C时仍能保持硬度，但在更高温度下会迅速软化。实验表明：高速钢切削低碳钢时，如速度超过1.8m/s(350ft/min),就会很快失效，而且许多高速钢材料在速度超过0.75m/s(150ft/min)时，就不能成功切削低碳钢。

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3.硬质合金：这是20世纪20年代晚期德国出现的硬质合金刀具，通常是将碳化钨或碳化钨和碳化钛或碳化钽的混合物以粉末形式沉积在鈷或镍的基体上。因为较高成本和较低的断裂强度，它们通常以刀片形式铜焊在钢质刀柄上或机械夹持在特质夹具撒上。机夹形式刀头经常做成不重磨形式，当所有刀刃都用废时，就将刀片丢弃，因为重磨成本比新刀片的成本高得多。

硬质合金刀具在高温时具有高硬度，故它们的切削速度比高速钢高得多，切削低碳钢时为3～4m/s(600-800ft/min),它们有几种牌号专用于大多数加工场合。韧性更高的硬质合金大大克服了早期产品的脆性，故也能用于断续切削，包括许多费力的面铣加工。最近，已经出现碳化钛或氮化钛涂层碳化钨刀具（涂层大约厚0.0005mm）。这些刀具比普通碳化钨硬质合金刀具更耐磨，使用氮化钛涂层界面摩擦力减小，导致切削力和刀具温度降低。因此，不降低刀具寿命就可得到较高的金属切削率，或不改变金属切削率而延长刀具寿命。

使用氧化铝涂层和多晶氮化硼的其他涂层尚处于实验阶段，但它们很可能在加工铸铁、淬硬钢和高熔点合金时有重要应用。

4.陶瓷：所谓的陶瓷刀具代表了刀具材料的最新进展，它们主要由烧结氧化物（通常是氧化铝）组成，而且几乎不变地做成夹持刀片。因为陶瓷刀片较便宜，而且刃磨时易引起热脆裂，所以都做成不重磨刀片。

陶瓷刀具是战后出现的，还没有在工厂里得到普遍应用。它们大都应用于高速切削中。陶瓷刀具能抑制积屑瘤的形成，能形成好的表面光洁度。因为现代机床的设计功率只能适合硬质合金刀具，目前，陶瓷只限于告诉精加工，此时，机床功率足够进行轻加工。陶瓷刀具特别脆，尽管目前已能进行铣削，陶瓷刀具主要还是限于连续切削。

陶瓷的热传导性比硬质合金差，因此，尽管前刀面上的摩擦力通常较低，但其前刀面的温度比硬质合金的要高得多。为了强化切削刃，进而改进刀具的寿命，经常在切削刃上做成一个小倒棱或圆弧，虽然这样做会增加功率消耗。

5.金刚石：金刚石刀具常用于加工有色金属如铜和铝，可得0.05～0.08um（2~3um）j极高的光洁度。金刚石用铜焊焊接在碳钢刀柄上。金刚石车削和镗孔是基本的精加工，因为任何（即使最轻）粗切削产生的李也会导致金刚石破裂或脱落。在适合的条件下，金刚石切削寿命最长。

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毕业设计（论文）报告纸

合成多晶金刚石目前已被用于机夹刀片上，因其成本太高，目前应用很少，但有时用于加工有磨蚀作用的铝、硅合金，熔融石英和增强塑料，随意的晶体取向改善了它们的冲击抗力，使它们适合断续切削。

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第三篇：毕业设计外文翻译

外文原文

Overview of JSp Technology

Benefits of JSp

JSp pages are translated into servlets.So, fundamentally, any task JSp pages can perform could also be accomplished by servlets.However, this underlying equivalence does not mean that servlets and JSp pages are equally appropriate in all scenarios.The issue is not the power of the technology, it is the convenience, productivity, and maintainability of one or the other.After all, anything you can do on a particular computer platform in the Java programming language you could also do in assembly language.But it still matters which you choose.JSp provides the following benefits over servlets alone:

•It is easier to write and maintain the HTML.Your static code is ordinary HTML: no extra backslashes, no double quotes, and no lurking Java syntax.•You can use standard Web-site development tools.Even HTML tools that know nothing about JSp can be used because they simply ignore the JSp tags.•You can divide up your development team.The Java programmers can work on the dynamic code.The Web developers can concentrate on the presentation layer.On large projects, this division is very important.Depending on the size of your team and the complexity of your project, you can enforce a weaker or stronger separation between the static HTML and the dynamic content.Now, this discussion is not to say that you should stop using servlets and use only JSp instead.By no means.Almost all projects will use both.For some requests in your project, you will use servlets.For others, you will use JSp.For still others, you will combine them with the MVC architecture.You want the appropriate tool for the job, and servlets, by themselves, do not complete your toolkit.Advantages of JSp Over Competing Technologies

A number of years ago, Marty was invited to attend a small 20-person industry roundtable discussion on software technology.Sitting in the seat next to Marty was James Gosling, inventor of the Java programming language.Sitting several seats away was a high-level manager from a very large software company in Redmond, Washington.During the discussion, the moderator brought up the subject of Jini, which at that time was a new Java technology.The moderator asked the manager what he thought of it, and the manager responded that it was too early to tell, but that it seemed to be an excellent idea.He went on to say that they would keep an eye on it, and if it seemed to be catching on, they would follow his company's usual “embrace and extend” strategy.At this point, Gosling lightheartedly interjected “You mean disgrace and distend.”

Now, the grievance that Gosling was airing was that he felt that this company would take technology from other companies and suborn it for their own purposes.But guess what? The shoe is on the other foot here.The Java community did not invent the idea of designing pages as a mixture of static HTML and dynamic code marked with special tags.For example, ColdFusion did it years earlier.Even ASp(a product from the very software company of the aforementioned manager)popularized this approach before JSp came along and decided to jump on the bandwagon.In fact, JSp not only adopted the general idea, it even used many of the same special tags as ASp did.So, the question becomes: why use JSp instead of one of these other technologies? Our first response is that we are not arguing that everyone should.Several of those other technologies are quite good and are reasonable options in some situations.In other situations, however, JSp is clearly better.Here are a few of the reasons.Versus.NET and Active Server pages(ASp)

.NET is well-designed technology from Microsoft.ASp.NET is the part that directly competes with servlets and JSp.The advantages of JSp are twofold.First, JSp is portable to multiple operating systems and Web servers;you aren't locked into deploying on Windows and IIS.Although the core.NET platform runs on a few non-Windows platforms, the ASp part does not.You cannot expect to deploy serious ASp.NET applications on multiple servers and operating systems.For some applications, this difference does not matter.For others, it matters greatly.Second, for some applications the choice of the underlying language matters greatly.For example, although.NET's C# language is very well designed and is similar to Java, fewer programmers are familiar with either the core C# syntax or the many auxiliary libraries.In addition, many developers still use the original version of ASp.With this version, JSp has a clear advantage for the dynamic code.With JSp, the dynamic part is written in Java, not VBScript or another ASp-specific language, so JSp is more powerful and better suited to complex applications that require reusable components.You could make the same argument when comparing JSp to the previous version of ColdFusion;with JSp you can use Java for the “real code” and are not tied to a particular server product.However, the current release of ColdFusion is within the context of a J2EE server, allowing developers to easily mix ColdFusion and servlet/JSp code.Versus pHp

pHp(a recursive acronym for “pHp: Hypertext preprocessor”)is a free, open-source, HTML-embedded scripting language that is somewhat similar to both ASp and JSp.One advantage of JSp is that the dynamic part is written in Java, which already has an extensive ApI for networking, database access, distributed objects, and the like, whereas pHp requires learning an entirely new, less widely used language.A second advantage is that JSp is much more widely supported by tool and server vendors than is pHp.Versus pure Servlets

JSp doesn't provide any capabilities that couldn't, in principle, be accomplished with servlets.In fact, JSp documents are automatically translated into servlets behind the scenes.But it is more convenient to write(and to modify!)regular HTML than to use a zillion println statements to generate the HTML.plus, by separating the presentation from the content, you can put different people on different tasks: your Web page design experts can build the HTML by using familiar tools and either leave places for your servlet programmers to insert the dynamic content or invoke the dynamic content indirectly by means of XML tags.Does this mean that you can just learn JSp and forget about servlets? Absolutely not!JSp developers need to know servlets for four reasons:

1.JSp pages get translated into servlets.You can't understand how JSp works without understanding servlets.2.JSp consists of static HTML, special-purpose JSp tags, and Java code.What kind of Java code? Servlet code!You can't write that code if you don't understand servlet programming.3.Some tasks are better accomplished by servlets than by JSp.JSp is good at generating pages that consist of large sections of fairly well structured HTML or other character data.Servlets are better for generating binary data, building pages with highly variable structure, and performing tasks(such as redirection)that involve little or no output.4.Some tasks are better accomplished by a combination of servlets and JSp than by either servlets or JSp alone.Versus JavaScript

JavaScript, which is completely distinct from the Java programming language, is normally used to dynamically generate HTML on the client, building parts of the Web page as the browser loads the document.This is a useful capability and does not normally overlap with the capabilities of JSp(which runs only on the server).JSp pages still include SCRIpT tags for JavaScript, just as normal HTML pages do.In fact, JSp can even be used to dynamically generate the JavaScript that will be sent to the client.So, JavaScript is not a competing technology;it is a complementary one.It is also possible to use JavaScript on the server, most notably on Sun ONE(formerly iplanet), IIS, and BroadVision servers.However, Java is more powerful, flexible, reliable, and portable.Versus WebMacro or Velocity

JSp is by no means perfect.Many people have pointed out features that could be improved.This is a good thing, and one of the advantages of JSp is that the specification is controlled by a community that draws from many different companies.So, the technology can incorporate improvements in successive releases.However, some groups have developed alternative Java-based technologies to try to address these deficiencies.This, in our judgment, is a mistake.Using a third-party tool like Apache Struts that augments JSp and servlet technology is a good idea when that tool adds sufficient benefit to compensate for the additional complexity.But using a nonstandard tool that tries to replace JSp is a bad idea.When choosing a technology, you need to weigh many factors: standardization, portability, integration, industry support, and technical features.The arguments for JSp alternatives have focused almost exclusively on the technical features part.But portability, standardization, and integration are also very important.For example, the servlet and JSp specifications define a standard directory structure for Web applications and provide standard files(.war files)for deploying Web applications.All JSp-compatible servers must support these standards.Filters can be set up to apply to any number of servlets or JSp pages, but not to nonstandard resources.The same goes for Web application security settings.Besides, the tremendous industry support for JSp and servlet technology results in improvements that mitigate many of the criticisms of JSp.For example, the JSp Standard Tag Library and the JSp 2.0 expression language address two of the most well-founded criticisms: the lack of good iteration constructs and the difficulty of accessing dynamic results without using either explicit Java code or verbose jsp:useBean elements.10.4 Misconceptions About JSp

Forgetting JSp Is Server-Side Technology

Here are some typical questions Marty has received(most of them repeatedly).•Our server is running JDK 1.4.So, how do I put a Swing component in a JSp page?

•How do I put an image into a JSp page? I do not know the proper Java I/O commands to read image files.•Since Tomcat does not support JavaScript, how do I make images that are highlighted when the user moves the mouse over them?

•Our clients use older browsers that do not understand JSp.What should we do?

•When our clients use “View Source” in a browser, how can I prevent them from seeing the JSp tags?

All of these questions are based upon the assumption that browsers know something about the server-side process.But they do not.Thus:

•For putting applets with Swing components into Web pages, what matters is the browser's Java version—the server's version is irrelevant.If the browser supports the Java 2 platform, you use the normal AppLET(or Java plug-in)tag and would do so even if you were using non-Java technology on the server.•You do not need Java I/O to read image files;you just put the image in the directory for Web resources(i.e., two levels up from WEB-INF/classes)and output a normal IMG tag.•You create images that change under the mouse by using client-side JavaScript, referenced with the SCRIpT tag;this does not change just because the server is using JSp.•Browsers do not “support” JSp at all—they merely see the output of the JSp page.So, make sure your JSp outputs HTML compatible with the browser, just as you would do with static HTML pages.•And, of course you need not do anything to prevent clients from seeing JSp tags;those tags are processed on the server and are not part of the output that is sent to the client.Confusing Translation Time with Request Time

A JSp page is converted into a servlet.The servlet is compiled, loaded into the server's memory, initialized, and executed.But which step happens when? To answer that question, remember two points:

•The JSp page is translated into a servlet and compiled only the first time it is accessed after having been modified.•Loading into memory, initialization, and execution follow the normal rules for servlets.Table 1 gives some common scenarios and tells whether or not each step occurs in that scenario.The most frequently misunderstood entries are highlighted.When referring to the table, note that servlets resulting from JSp pages use the _jspService method(called for both GET and pOST requests), not doGet or dopost.Also, for initialization, they use the jspInit method, not the init method.Table 1.JSp Operations in Various Scenarios

JSp page translated into servletServlet compiledServlet loaded into server's memoryjspInit called_jspService called

page first written

Request 1YesYesYesYesYes

Request 2NoNoNoNoYes

Server restarted

Request 3NoNoYesYesYes

Request 4NoNoNoNoYes

page modified

Request 5YesYesYesYesYes

Request 6NoNoNoNoYes

中文翻译

JSp技术概述

一、JSp的好处

JSp页面最终会转换成servler。因而，从根本上，JSp页面能够执行的任何任务都可以用servler来完成。然而，这种底层的等同性并不意味着servler和JSp页面对于所有的情况都等同适用。问题不在于技术的能力，而是二者在便利性、生产率和可维护性上的不同。毕竟，在特定平台上能够用Java编程语言完成的事情，同样可以用汇编语言来完成，但是选择哪种语言依旧十分重要。

和单独使用servler相比，JSp提供下述好处：

JSp中HTML的编写与维护更为简单。JSp中可以使用常规的HTML：没有额外的反斜杠，没有额外的双引号，也没有暗含的Java语法。

能够使用标准的网站开发工具。即使对那些对JSp一无所知的HTML工具，我们也可以使用，因为它们会忽略JSp标签（JSp tags）。

可以对开发团队进行划分。Java程序员可以致力于动态代码。Web开发人员可以将经理集中在表示层（presentation layer）上。对于大型的项目，这种划分极为重要。依据开发团队的大小，及项目的复杂程度，可以对静态HTML和动态内容进行弱分离（weaker separation）和强分离（stronger separation）。

在此，这个讨论并不是让您停止使用servlets，只使用JSp。几乎所有的项目都会同时用到这两种技术。针对项目中的某些请求，您可能会在MVC构架下组合使用这两项技术。我们总是希望用适当的工具完成相对应的工作，仅仅是servlet并不能填满您的工具箱。

二、JSp相对于竞争技术的优势

许多年前，Marty受到邀请,参加一个有关软件技术的小型(20个人)研讨会.做在Marty旁边的人是James Gosling---Java编程语言的发明者。隔几个位置,是来自华盛顿一家大型软件公司的高级经理。在讨论过程中,研讨会的主席提出了Jini的议题,这在当时是一项新的Java技术.主席向该经理询问他的想法.他继续说,他们会持续关注这项技术,如果这项技术变得流行起来,他们会遵循公司的“接受并扩充(embrace and extend)”的策略.此时, Gosling随意地插话说“你的意思其实就是不接受且不扩充(disgrace and distend)。”

在此, Gosling的抱怨显示出，他感到这个公司会从其他公司那里拿走技术,用于他们自己的目的.但你猜这次怎么样?这次鞋子穿在了另一只脚上。Java社团没有发明这一思想----将页面设计成由静态HTML和用特殊标签标记的动态代码混合组成.。ColdFusion多年前就已经这样做了。甚至ASp(来自于前述经理所在公司的一项产品)都在JSp出现之前推广了这种方式。实际上,JSp不只采用了这种通用概念,它甚至使用许多和ASp相同的特殊标签。

因此,问题变成:为什么使用JSp,而不使用其他技术呢?我们的第一反应是我们不是在争论所有的人应该做什么。其他这些技术中,有一些也很不错,在某些情况下也的确是合情合理的选择.然而,在其他情形中,JSp明显要更好一些。下面给出几个理由。

与.NET和Active Server pages(ASp)相比

.NET是Microsoft精心设计的一项技术。ASp.NET是与servlets和JSp直接竞争的技术。JSp的优势体现在两个方面。

首先,JSp可以移植到多种操作系统和Web服务器,您不必仅仅局限于部署在Windows 和IIS上尽管核心.NET平台可以在好几种非Windows平台上运行，但ASp这一部分不可以。您不能期望可以将重要的ASp.NET应用部署到多种服务器和操作系统。对于某些应用，这种差异没有什么影响。但有些应用，这种差异却非常重要。

其次，对于某些应用，底层语言的选择至关重要。例如，尽管.NET的C#语言设计优良，且和Java类似，但熟悉核心C#语法和众多工具库的程序员很少。此外,许多开发者依旧使用最初版本的ASp。相对于这个版本,JSp在动态代码方面拥有明显的优势。使用JSp,动态部分是用Java编写的,而非VBScript过其他ASp专有的语言,因此JSp更为强劲,更适合于要求组件重用的复杂应用。

当将JSp与之前版本的ColdFusion对比时，您可能会得到相同的结论。应用JSp，您可以使用Java编写“真正的代码”，不必依赖于特定的服务器产品。然而，当前版本的ColdFusion满足J2EE服务器的环境，允许开发者容易的混合使用ColdFusion和Servlet/JSp代码。

与pHp相比

pHp（“pHp：Hypertext preprocessor”的递归字母缩写词）是免费的、开放源代码的、HTML嵌入其中的脚本语言，与ASp和JSp都有某种程度的类似。JSp的一项优势是动态部分用Java编写，而Java已经在联网、数据库访问、分布式对象等方面拥有广泛的ApI，而pHp需要学习全新的、应用相对广泛的语言。JSp的第二项优势是，和pHp相比，JSp拥有极为广泛的工具和服务器提供商的支持。

与纯Servlet相比

原则上，JSp并没有提供Servlet不能完成的功能。实际上，JSp文档在后台被自动转换成Servlet。但是编写（和修改）常规的HTML，要比无数println语句生成HTML要方便得多。另外，通过将表示与内容分离，可以为不同的人分配不同的任务：网页设计人员使用熟悉的工具构建HTML，要么为Servlet程序员留出空间插入动态内容，要么通过XML标签间接调用动态内容。

这是否表示您只可以学习JSp，将Servlet丢到一边呢？当然不是！由于以下4种原因，JSp开发人员需要了解Servlet：

（1）JSp页面会转换成Servlet。不了解Servlet就无法知道JSp如何工作。

（2）JSp由静态HTML、专用的JSp标签和Java代码组成。哪种类型的Java代码呢？当然是Servlet代码！如果不了解Servlet编程，那么就无法编写这种代码。

（3）一些任务用Servlet完成比用JSp来完成要好。JSp擅长生成由大量组织有序的结构化HTML或其他字符数据组成的页面。Servlet擅长生成二进制数据，构建结构多样的页面，以及执行输出很少或者没有输出的任务（比如重定向）。

（4）有些任务更适合于组合使用Servlet和JSp来完成，而非单独使用Servlet或JSp。

与JavaScript相比

JavaScript和Java编程语言完全是两码事，前者一般用于在客户端动态生成HTML，在浏览器载入文档时构建网页的部分内容。这是一项有用的功能，一般与JSp的功能（只在服务器端运行）并不发生重叠。和常规HTML页面一样，JSp页面依旧可以包括用于JavaScript的SCRIpT标签。实际上，JSp甚至能够用来动态生成发送到客户端的JavaScript。因此，JavaScript不是一项竞争技术，它是一项补充技术。

JavaScript也可以用在服务器端，最因人注意的是SUN ONE（以前的iplanet）、IIS和BroadVision服务器。然而，Java更为强大灵活、可靠且可移植。

与WebMacro和Velocity相比

JSp决非完美。许多人都曾指出过JSp中能够改进的功能。这是一件好事，JSp的优势之一是该规范由许多不同公司组成的社团控制。因此，在后续版本中，这项技术能够得到协调的改进。

但是，一些组织已经开发出了基于Java的替代技术，试图弥补这些不足。据我们的判断，这样做是错误的。使用扩充JSp和Servlet技术的第三方工具，如Apache Structs，是一种很好的思路，只要该工具带来的好处能够补偿工具带来的额外复杂性。但是，试图使用非标准的工具代替JSp则不理想。在选择一项技术时，需要权衡许多方面的因素：标准化、可移植性、集成性、行业支持和技术特性。对于JSp替代技术的争论几乎只是集中在技术特性上，而可移植性、标准化和集成性也十分重要。例如，Servlet和JSp规范为Web应用定义了一个标准的目录结构，并提供用于部署Web应用的标准文件（.war文件）。所有JSp兼容的服务器必须支持这些标准。我们可以建立过滤器作用到任意树木的Servlet和JSp页面上，但不能用于非标准资源。Web应用安全设置也同样如此。

此外，业界对JSp和Servlet技术的巨大支持使得这两项技术都有了巨大的进步，从而减轻了对JSp的许多批评。例如，JSp标准标签库和JSp 2.0表达式语言解决了两种最广泛的批评：缺乏良好的迭代结构；不使用显式的Java代码或冗长的jsp:useBean元素难以访问动态结果。

三、对JSp的误解

忘记JSp技术是服务器端技术

下面是Marty收到的一些典型问题（大部分问题不止一次的出现）。

我们的服务器正在运行JDK1.4。我如何将Swing组件用到JSp页面中呢？

我如何将图像放到JSp页面中？我不知道读取图像文件应该使用哪些Java I/O命令。

Tomcat不支持JavaScript，当用户在图像上移动鼠标时，我如何使图像突出显示呢？

我们的客户使用不理解JSp的旧浏览器。我应该怎么做？

当我们的客户在浏览器中使用“View Source”（查看源代码）时，如何阻止他们看到JSp标签？

所有这些问题都基于浏览器对服务器端的过程在有所了解的假定之上。但事实上浏览器并不了解服务器端的过程。因此：

如果要将使用Swing组件的applet放到网页中，重要的是浏览器的Java版本，和服务器的Java版本无关。如果浏览器支持Java 2平台，您可以使用正常的AppLET（或Java插件）标签，即使在服务器上使用了非Java技术也须如此。

您不需要Java I/O来读取图像文件，您只需将图像放在存储Web资源的目录中（即WEB-INF/classes向上两级的目录），并输出一个正常的IMG标签。

您应该用SCRIpT标签，使用客户端JavaScript创建在鼠标下会更改的图像，这不会由于服务器使用JSp而改变。

浏览器根本不“支持”JSp----它们看到的只是JSp页面的输出。因此，如同对待静态HTML页面一样，只需确保JSp输出的HTML与浏览器兼容。

当然，您不需要采取什么措施来阻止客户看到JSp标签，这些标签在服务器上进行处理，发送给客户的输出中并不出现。

混淆转换期间和请求期间

JSp页面需要转换成servlet。Servlet在编译后，载入到服务器的内容中，初始化并执行。但是每一步发生在什么时候呢？要回答这个问题，要记住以下两点：

JSp页面仅在修改后第一次被访问时，才会被转换成servlet并进行编译；

载入到内存中、初始化和执行遵循servlet的一般规则。

表1列出一些常见的情形，讲述在该种情况下每一步是否发生。最常被误解的项已经突出标示出来。在参考该表时，要注意，由JSp页面生成的servlet使用_jspService方法（GET和pOST请求都调用该函数），不是doGet或dopost方法。同样，对于初始化，它们使用jspInit方法，而非init方法。

表1 各种情况下的JSp操作

将JSp 页面转换成servlet编译Servlet 将Servlet 载入到服务器内存中调用jspInit 调用_jspService

页面初次创建

请求 1有有有有有

请求 2无无无无有

服务器重启后

请求3无无有有有

请求 4无无无无有

页面修改后

请求 5有有有有有

请求 6无无无无有

第四篇：计算机英语论文翻译毕业设计

DATA WAREHOUSE

Data warehousing provides architectures and tools for business executives to systematically organize, understand, and use their data to make strategic decisions.A large number of organizations have found that data warehouse systems are valuable tools in today's competitive, fast evolving world.In the last several years, many firms have spent millions of dollars in building enterprise-wide data warehouses.Many people feel that with competition mounting in every industry, data warehousing is the latest must-have marketing weapon —— a way to keep customers by learning more about their needs.“So“, you may ask, full of intrigue, “what exactly is a data warehouse?”

Data warehouses have been defined in many ways, making it difficult to formulate a rigorous definition.Loosely speaking, a data warehouse refers to a database that is maintained separately from an organization's operational databases.Data warehouse systems allow for the integration of a variety of application systems.They support information processing by providing a solid platform of consolidated, historical data for analysis.According to W.H.Inmon, a leading architect in the construction of data warehouse systems, “a data warehouse is a subject-oriented, integrated, time-variant, and nonvolatile collection of data in support of management's decision making process.“ This short, but comprehensive definition presents the major features of a data warehouse.The four keywords, subject-oriented, integrated, time-variant, and nonvolatile, distinguish data warehouses from other data repository systems, such as relational database systems, transaction processing systems, and file systems.Let's take a closer look at each of these key features.(1)Subject-oriented: A data warehouse is organized around major subjects, such as customer, vendor, product, and sales.Rather than concentrating on the day-to-day operations and transaction processing of an organization, a data warehouse focuses on the modeling and analysis of data for decision makers.Hence, data warehouses typically provide a simple and concise view around particular subject issues by excluding data that are not useful in the decision support process.(2)Integrated: A data warehouse is usually constructed by integrating multiple heterogeneous sources, such as relational databases, flat files, and on-line transaction records.Data cleaning and data integration techniques are applied to ensure consistency in naming conventions, encoding structures, attribute measures, and so on..(3)Time-variant: Data are stored to provide information from a historical perspective(e.g., the past 5-10 years).Every key structure in the data warehouse contains, either implicitly or explicitly, an element of time.(4)Nonvolatile: A data warehouse is always a physically separate store of data transformed from the application data found in the operational environment.Due to this separation, a data warehouse does not require transaction processing, recovery, and concurrency control mechanisms.It usually requires only two operations in data accessing: initial loading of data and access of data..In sum, a data warehouse is a semantically consistent data store that serves as a physical implementation of a decision support data model and stores the information on which an enterprise needs to make strategic decisions.A data warehouse is also often viewed as an architecture, constructed by integrating data from multiple heterogeneous sources to support structured and/or ad hoc queries, analytical reporting, and decision making.“OK”, you now ask, “what, then, is data warehousing?“

Based on the above, we view data warehousing as the process of constructing and using data warehouses.The construction of a data warehouse requires data integration, data cleaning, and data consolidation.The utilization of a data warehouse often necessitates a collection of decision support technologies.This allows “knowledge workers”(e.g., managers, analysts, and executives)to use the warehouse to quickly and conveniently obtain an overview of the data, and to make sound decisions based on information in the warehouse.Some authors use the term “data warehousing“ to refer only to 1 the process of data warehouse construction, while the term warehouse DBMS is used to refer to the management and utilization of data warehouses.We will not make this distinction here.“How are organizations using the information from data warehouses?” Many organizations are using this information to support business decision making activities, including:

(1)increasing customer focus, which includes the analysis of customer buying patterns(such as buying preference, buying time, budget cycles, and appetites for spending).(2)repositioning products and managing product portfolios by comparing the performance of sales by quarter, by year, and by geographic regions, in order to fine-tune production strategies.(3)analyzing operations and looking for sources of profit.(4)managing the customer relationships, making environmental corrections, and managing the cost of corporate assets.Data warehousing is also very useful from the point of view of heterogeneous database integration.Many organizations typically collect diverse kinds of data and maintain large databases from multiple, heterogeneous, autonomous, and distributed information sources.To integrate such data, and provide easy and efficient access to it is highly desirable, yet challenging.Much effort has been spent in the database industry and research community towards achieving this goal.The traditional database approach to heterogeneous database integration is to build wrappers and integrators(or mediators)on top of multiple, heterogeneous databases.A variety of data joiner and data blade products belong to this category.When a query is posed to a client site, a metadata dictionary is used to translate the query into queries appropriate for the individual heterogeneous sites involved.These queries are then mapped and sent to local query processors.The results returned from the different sites are integrated into a global answer set.This query-driven approach requires complex information filtering and integration processes, and competes for resources with processing at local sources.It is inefficient and potentially expensive for frequent queries, especially for queries requiring aggregations.Data warehousing provides an interesting alternative to the traditional approach of heterogeneous database integration described above.Rather than using a query-driven approach, data warehousing employs an update-driven approach in which information from multiple, heterogeneous sources is integrated in advance and stored in a warehouse for direct querying and analysis.Unlike on-line transaction processing databases, data warehouses do not contain the most current information.However, a data warehouse brings high performance to the integrated heterogeneous database system since data are copied, preprocessed, integrated, annotated, summarized, and restructured into one semantic data store.Furthermore, query processing in data warehouses does not interfere with the processing at local sources.Moreover, data warehouses can store and integrate historical information and support complex multidimensional queries.As a result, data warehousing has become very popular in industry.1.Differences between operational database systems and data warehouses

Since most people are familiar with commercial relational database systems, it is easy to understand what a data warehouse is by comparing these two kinds of systems.The major task of on-line operational database systems is to perform on-line transaction and query processing.These systems are called on-line transaction processing(OLTP)systems.They cover most of the day-to-day operations of an organization, such as, purchasing, inventory, manufacturing, banking, payroll, registration, and accounting.Data warehouse systems, on the other hand, serve users or “knowledge workers“ in the role of data analysis and decision making.Such systems can organize and present data in various formats in order to accommodate the diverse needs of the different users.These systems are known as on-line analytical processing(OLAP)systems.The major distinguishing features between OLTP and OLAP are summarized as follows.(1)Users and system orientation: An OLTP system is customer-oriented and is used for transaction and query processing by clerks, clients, and information technology professionals.An OLAP system is market-oriented and is used for data analysis by knowledge workers, including managers, executives, and analysts.(2)Data contents: An OLTP system manages current data that, typically, are too detailed to be easily used for decision making.An OLAP system manages large amounts of historical data, provides 2 facilities for summarization and aggregation, and stores and manages information at different levels of granularity.These features make the data easier for use in informed decision making.(3)Database design: An OLTP system usually adopts an entity-relationship(ER)data model and an application-oriented database design.An OLAP system typically adopts either a star or snowflake model, and a subject-oriented database design.(4)View: An OLTP system focuses mainly on the current data within an enterprise or department, without referring to historical data or data in different organizations.In contrast, an OLAP system often spans multiple versions of a database schema, due to the evolutionary process of an organization.OLAP systems also deal with information that originates from different organizations, integrating information from many data stores.Because of their huge volume, OLAP data are stored on multiple storage media.(5).Access patterns: The access patterns of an OLTP system consist mainly of short, atomic transactions.Such a system requires concurrency control and recovery mechanisms.However, accesses to OLAP systems are mostly read-only operations(since most data warehouses store historical rather than up-to-date information), although many could be complex queries.Other features which distinguish between OLTP and OLAP systems include database size, frequency of operations, and performance metrics and so on.2.But, why have a separate data warehouse?

“Since operational databases store huge amounts of data”, you observe, “why not perform on-line analytical processing directly on such databases instead of spending additional time and resources to construct a separate data warehouse?“

A major reason for such a separation is to help promote the high performance of both systems.An operational database is designed and tuned from known tasks and workloads, such as indexing and hashing using primary keys, searching for particular records, and optimizing “canned” queries.On the other hand, data warehouse queries are often complex.They involve the computation of large groups of data at summarized levels, and may require the use of special data organization, access, and implementation methods based on multidimensional views.Processing OLAP queries in operational databases would substantially degrade the performance of operational tasks.Moreover, an operational database supports the concurrent processing of several transactions.Concurrency control and recovery mechanisms, such as locking and logging, are required to ensure the consistency and robustness of transactions.An OLAP query often needs read-only access of data records for summarization and aggregation.Concurrency control and recovery mechanisms, if applied for such OLAP operations, may jeopardize the execution of concurrent transactions and thus substantially reduce the throughput of an OLTP system.Finally, the separation of operational databases from data warehouses is based on the different structures, contents, and uses of the data in these two systems.Decision support requires historical data, whereas operational databases do not typically maintain historical data.In this context, the data in operational databases, though abundant, is usually far from complete for decision making.Decision support requires consolidation(such as aggregation and summarization)of data from heterogeneous sources, resulting in high quality, cleansed and integrated data.In contrast, operational databases contain only detailed raw data, such as transactions, which need to be consolidated before analysis.Since the two systems provide quite different functionalities and require different kinds of data, it is necessary to maintain separate databases.数据仓库

数据仓库为商务运作提供了组织结构和工具，以便系统地组织、理解和使用数据进行决策。许多组织发现在如今的具有竞争与快速发展的世界中数据仓库是非常有用的工具。

在最近的几年里，许多公司花了几百万美元用于构建企业数据库。许多人也认为随着竞争加剧，数据仓库己成为营销必备的手段——一种了解顾客的需求的武器。

“那么”，你可能会充满神秘地问，“到底什么是数据仓库？”

数据仓库有不同的定义，但却很难有一个严格的定义。不严谨的说，数据仓库是一个数据库，它与组织机构的操作数据库分别维护。数据仓库允许不同应用系统的集成，为统一的历史数据分析提供坚实的平台，对信息处理提供支持。

按照W.H Inmon,一位数据仓库构造方面的领头建筑师说，“数据仓库是一个面向主题的、集成的、随时间变化的、非易失的数据的集合，支持管理决策制定。”这个简短，但是复合的定义表述了数据仓库的主要特点。四个关键词，面向主题的、集成的、时变的、非易失的，将数据仓库与其它数据存储系统相区别。让我们进下来认识它的四个特征。

(1)面向对象：数据仓库是围绕一些主题，如顾客、供应商、产品和销售组织。数据仓库关注决策者的数据建模与分析，而不是构造机构日常操作和事务处理。因此，数据仓库排除了在进程中提供的没有价值的决策。

(2)集成的：数据仓库通常由多个数据源组成，如关系数据库、一般文件和联机事务处理记录。数据清理和数据集成技术被运用于确保命名的合理性、代码的结构，结构尺度等。

(3)随时间变化：数据被存储是用来提供变化历史角度的信息。数据仓库中所包含的关键字，都显性或隐性的反映时间元素。

(4)非易失性：数据仓库是物理地分离存放数据；基于这种分法，数据仓库不需要传输进程，覆盖和并发控制机制。它通常只需要两种数据访问：数据的初使化装入和数据访问。

总得来说，数据仓库是一种语义上一致的数据存储，它充当了物理决策数据模型的实施关于哪种企业需要做战略决策。数据仓库经常被认作一种结构，由集成的数据组合而成，支持结构化和启发式查询、分析报告和决策制定。

“好”，“现在你可以问什么是数据仓库。”

基于以上所讲的，我们把数据仓库视为构造和使用数据仓库的过程。数据仓库的构造需要数据集成、数据清理和数据统一。利用数据仓库常常需要一些决策支持技术。这使得知识工作者能够利用数据仓库，快捷方便地得到数据总体视图，根据数据仓库中的信息做出准确的决策。有些人使用术语“建立数据库”表示构造数据仓库的过程，用仓库DBMS表示管理和使用数据仓库。我们将不区分二者。

“组织是如何从数据仓库中使用数据的？”许多组织使用这些信息支持决策活动，包括：

(1)增加顾客关注，包括分析顾客购买模式（如，喜爱买什么、购买时间、预算周期、消费习惯）;(2)根据季度、年、地区的营销情况比较，重新配置产品和管理投资，调整生产策略；

(3)分析运作和查找利润源；

(4)管理顾客关系、进行环境调整、管理合股人的资产开销。

从异种数据库集成的角度看，数据仓库也是十分有用的。许多组织收集了不同类的数据，并由多个异种的、自治的、分布的数据源维护大型数据库。集成这些数据，并提供简便、有效的访问是非常希望的，并且也是一种挑战。数据库工业界和研究界都正朝着实现这一目标竭尽全力。

对于异种数据库的集成，传统的数据库做法是：在多个异种数据库上，建立一个包装程序和一个集成程序（或仲裁程序）。这方面的例子包括IBM 的数据连接程序 和Informix的数据刀。当一个查询提交客户站点，首先使用元数据字典对查询进行转换，将它转换成相应异种站点上的查询。然后，将这些查询映射和发送到局部查询处理器。由不同站点返回的结果被集成为全局回答。这种查询驱动的方法需要复杂的信息过滤和集成处理，并且与局部数据源上的处理竞争资 5 源。这种方法是低效的，并且对于频繁的查询，特别是需要聚集操作的查询，开销很大。

对于异种数据库集成的传统方法，数据仓库提供了一个有趣的替代方案。数据仓库使用更新驱动的方法，而不是查询驱动的方法。这种方法将来自多个异种源的信息预先集成，并存储在数据仓库中，供直接查询和分析。与联机事务处理数据库不同，数据仓库不包含最近的信息。然而，数据仓库为集成的异种数据库系统带来了高性能，因为数据被拷贝、预处理、集成、注释、汇总，并重新组织到一个语义一致的数据存储中。在数据仓库中进行的查询处理并不影响在局部源上进行的处理。此外，数据仓库存储并集成历史信息，支持复杂的查询。这样，建立数据仓库在工业界就非常流行。1.操作数据库系统与数据仓库的区别

由于大多数人都熟悉商品关系数据库系统，将数据仓库与之比较，就容易理解什么是数据仓库。

联机操作数据库系统的主要任务是执行联机事务和查询处理。这种系统称为联机事务处理（OLTP）系统。它们涵盖了一个组织的大部分日常操作，如购买、库存、制造、银行、工资、注册、记帐等。另一方面，数据仓库系统在数据分析和决策方面为用户或“知识工人”提供服务。这种系统可以用不同的格式组织和提供数据，以便满足不同用户的形形色色需求。这种系统称为联机分析处理（OLAP）系统。

OLTP 和OLAP 的主要区别概述如下。

（1）用户和系统定位：联机事务处理是以顾客为导向，用于给客户和信息技术专家

传输和职员查询处理。在线分析系统是以市场为导向，用于知识工作者包括管理员、执行官和分析员处理数据。

（2）数据内容：联机事务处理系统管理当前数据，特别的，都是一些详细并且简单可以用于做决定。在线分析系统管理大量历史数据，提供总结和聚集的设备，存储和管理不同水平的粒度。这些特征使得用户在做决策上更简单。

（3）数据库的设计：联机处理系统通常采用实体数据模型和应用联机系统数据设计。在线分析系统采用星形或雪花模型和面向主题的数据库设计。

6（4）视图：联机事务处理系统聚焦于当前企业或部门数据，而不涉及到历史数据或在不同组织中的数据。总得来说，在线分析系统经常跨越许多数据库版本，基于组织机构的改革。在线分析系统同样处理来自不同组织的数据，从大量数据存储中整合信息。由于体积的庞大，在线分析系统在多个数据媒体上建立存储。

（5）存储模式：联机处理系统组成短小，自动交易。如此的一个系统需要并发控制和恢复机制。然而，在线分析系统存储大部分是只读的，尽管大部分可以复杂查询。

其它区分联机处理系统和在线分析系统包括数据大小，操作的频率，性能的指标。

2.但是，为什么需要一个分离的数据库？

“既然操作数据库存储了大量的数据”，你也看到了，“为什么不直接执行在线分析系统数据库替代花费大量时间和资源去构建一个分离的数据库？ 这种分离的一个主要的原因是可以提高两个系统的性能。操作数据库是在己知的任务和负载设计的，如果用主关键字索引和散列，检索特定的记录和优化“罐装”的查询。另一方面，数据仓库查询通常是复杂的。它们涉及了一堆数据总括水平的大量运算，它们中的一些需要特殊的算法，存储和基于多维视图的实现方法。在线分析系统进程查询在操作数据中可能需要降解大量的操作工作。

另外，操作数据库支持几个交易的并行处理。并行控制和恢复机制，比如锁定和测量，都需要确保交易的一致性和稳定性。在线分析系统查询通常需要对数据记录进行只读访问，以进行汇总和聚集。并行控制和恢复机制，如果应用于联机处理系统，可能会危害控制交易的执行，那样的话，会大大地了降低在线分析系统的吞吐量。

最后，从数据仓库中分离数据的操作是基于不同的数据结构，内容和用法。决策支持系统需要历史的数据，而操作数据库一般不保存历史数据。在这里，在操作系统中的数据尽管很多，但对于决策，常常还是不够的。决策支持系统需要把从异构数据中得来的数据进行统一，才能得以高效的查询，纯净的和集成的数据。相比之下，操作数据库包含的不仅仅是原始数据，比如交易数据，这些数据在进行分析之前需要统一。由于两系统提供的功能不一样，需要不同类型的数据，因此需要维护分离的数据库。

第五篇：毕业设计冷凝器外文翻译

吉林化工学院本科毕业设计（论文）外文翻译

氨制冷系统的节能设计，改造和蒸发式冷凝器的控制

阿卜杜勒穆罕默德和凯利，工业评估中心，代顿大学

摘要

氨制冷系统通常提供了许多节能商机，因为他们的大动力消耗，运行时间长的和动态的操作。氨制冷系统的能源使用高度依赖于冷凝头的压力，而这是一个函数的蒸发式冷凝器容量和控制功能。本文研究系统能源利用中聚光能力和冷凝器的控制之间的关系。它首先开发方法来确定冷凝器的性能，然后以仿真模型模拟压缩机和冷凝器风扇的能源利用。，它使用工程基本面和经验两个数据，准确地捕捉压缩机，冷凝器和环境湿球温度之间的协同效应。节约能源是三种情况：安装在冷凝器风机变频驱动器，采用湿球控制方法战略和提高聚光性能。以说明气候的影响，这些模拟是两个不同的ASHRAE气候区，迈阿密，佛罗里达州和执行明尼阿波利斯，明尼苏达州，这是炎热和寒冷的气候分别。结果表明，提高表现不佳的冷凝器的性能是最经济有效的节能测量。但是节约能源从冷凝器安装变频驱动器球迷和利用湿球的方法策略取决于环境气候条件，与位置无关。接下来，内部收益率的计算方法来安装额外的聚光能力超越在为相同的两个ASHRAE气候区新建筑应用的标准做法。结果表明，安装两次基线聚光能力，内部收益率超过20 ％。综上所述，本文提出的设计，改造的综合方法在氨制冷系统蒸发式冷凝器的控制权。节约能源衍生通过使用这种方法可以显著提高氨的能量效率制冷系统。

介绍

约7.5 ％的总生产能耗用于食品加工行业，其中约21％的能量是电能(二零零六年环评)。在这些设备中，氨制冷系统是最大的能源消耗部分。制冷与冷却工艺所用电量是食品加工行业(二零零六年EIA)的用电量的27％。制冷系统使用的能量是高度依赖于冷凝压力，而这又是冷凝器容量和控制性能。因此，提高聚光能力和控制可导致显著的节能效果。

本文首先确定使用的数据从实际的聚光性能制冷控制系统。然后是开发仿真模型来计算每年的能源使用所研究的压缩机和冷凝器风扇。该仿真模型，用来计算节能三

吉林化工学院本科毕业设计（论文）外文翻译

个节能措施(ECMS)：在冷凝器风扇安装变频器，采用湿球的方法策略，提高聚光性能。以说明气候的影响，这些仿真用于执行迈阿密，佛罗里达州和明尼苏达州明尼阿波利斯，这是炎热和寒冷的气候分别。文章最后决定回报的安装额外的容量超出标准规范的内部收益率在新的建筑应用。

系统说明

分析系统是一个两阶段的氨制冷系统具有两个低压侧压缩机和两个高级压缩机。所有的压缩机是螺杆式与滑阀控制和热虹吸油冷却。一种蒸发式冷凝器以恒定的速度从系统散发热量。对于本文的其余部分，术语系统将参考冷凝器风扇和压缩机。从冷凝器泵的能源使用小，并且不评价了本文。关键系统参数，包括电动机电流，氨的压力和温度从制冷控制系统获得。氨性数据的计算使用参考流体热力学和输运性质数据(NIST，2010)也被称为REFPROP。图中显示了制冷系统的替补的示意图。

图1。电路图制冷系统的pH值图上

计算排热到冷凝器

冷凝压力是决定系统能源利用的一个关键变量。为了准确地计算冷凝压力，冷凝器性能必须确定。在第一步骤中确定冷凝器性能是计算从压缩机排出到总热量冷凝器。在系统中的能量平衡显示了总的热拒绝了冷凝器是由低和高级压缩机加两个设置在制冷（QREF0）低和高级压缩机两者的压缩或轴功率（WS）的热量。

QCond.actual = Σ QrefLS +Σ QrefHS +Σ WSLS +Σ WsHS（1）

吉林化工学院本科毕业设计（论文）外文翻译

所有的热拒绝从低温压缩机减去热虹吸拒绝的低级压缩机油冷却（TSOC，LS）将被转移到高压侧制度。因此，由高温压缩机提供（TRprovided，HS）的制冷是：

ΣTRprovided，HS = Σ QrefLS +Σ QrefHS +Σ WLS

吉林化工学院本科毕业设计（论文）外文翻译

量可以使用等式4和来自控制系统的百分之制冷容量，计算如下：

QREF = Qrrated • ％容量

（5）

压缩热由高温级压缩机（WsHS）生产

来自控制系统的数据而获得的每个压缩机的电机电流。至相关电机电流轴功率（WS），电机电流和输入之间的关系权力必须得到发展。这种关系中，可以从点测量开发电机电流和输入功率在整个压缩机的工作范围。通过使用的压缩机（ὴm）的两个铭牌效率和f（A），轴功率或等价每个压缩机的压缩热量可以计算为：

WsHS = F（A）* ὴm

（6）

热虹吸油冷却（TSOC）

考虑了两阶段的低温循环在图1中表示的氨制冷系统。在状态1LS，氨进入压缩机作为饱和蒸汽和离开压缩机的过热蒸汽在状态2LS。路径1LSmref.LS •（h2a.LSh4.LS）（8）

通常，制造商报告的体积流量的空气速率，标称容量，并且热抑制因子（HRF）。体积流量是用于使用计算的质量流率空气的密度在标准条件。该HRF，这既是外部空气湿球温度计的功能温度（TWB）和饱和冷凝温度（Tcond），用于确定在额定容量冷凝器对于一个给定TWB和Tcond为（Manske，Reindl和2001年克莱因）：

额定电容容量=标称容量/ HRF（TWB，Tcond）（10）

等式9b和10可以适用于制造商的规格为蒸发冷凝器，以确定对于一个给定的湿球Tcond和效力之间的关系范围。有效性被发现是线性相关的Tcond为： effM = E0

吉林化工学院本科毕业设计（论文）外文翻译

由于蒸发式冷凝器的运行期间的实际容量已计算的，实际效果可以适合于在等式11的形式的线。测量效力与从所研究的系统Tcond数据被绘制时，无论是蒸发式冷凝器，风机和水泵是在图3满负荷生产。额定制造商从式（11）效果也绘制在同一张图来比较的有效性上一个新的蒸发式冷凝器，以其中一个已经服役了几年。图3表示该蒸发式冷凝器性能已劣化随着时间的推移。实际容量比制造商的额定容量少约40％。此信息可以被用作用于模拟程序的校准参数。例如，在图3中，冷凝器容量为一个新的冷凝器将约为1.69倍，目前的实际能力。

图3。实际和制造商有效性的蒸发式冷凝器

模拟年能源消耗

每年的能量使用的制冷系统的是压缩机和冷凝器的总和风机能耗。冷凝压力是必须正确地计算一个关键的变量正确模拟压缩机和冷凝器风扇的能源使用。以下步骤概述一方法计算压缩机功率，冷凝压力和冷凝器风扇电源。

计算压缩机输入功率

一个给定的压缩机在一定范围抽吸的额定轴功率（bhprated）和冷凝温度可以从制造商处获得。此数据可以被嵌入到一个二阶多项式方程的交互项来确定额定满载

吉林化工学院本科毕业设计（论文）外文翻译

轴功率在给定的吸气和冷凝温度（Manske 2000），如：

bhprated = P0 + P1 • Tcond + P2 • TSUC + P11 • Tcond ² + P22 • TSUC ² + P12 • Tcond • TSUC（12）

在该制冷系统中的压缩机，像许多制冷系统中，在操作碱/修剪方式，表示过去压缩机接通的每个阶段是修剪压缩机。式（4），它类似于公式12中，示出的满负荷容量压缩机吸入的函数和冷凝温度下，该压缩机运行。知道制冷负荷（参考负载）和碱的量被操作（Σ TRBase），则该部分的容量修剪压缩机的压缩机定阶段（FCTrim）可以计算如下：

FCTrim =（参考负载6789

吉林化工学院本科毕业设计（论文）外文翻译

红色=压缩机的能耗，蓝=冷凝器风扇能源，绿色=节能，广场=投资回报率，VFD =常数变速冷凝器风扇，所需时间约=利用湿球的方法和策略PERFOR =提高聚光性能。

在新建筑应用安装额外的电容容量

冷凝器是因为结构支撑，管道和控制成本来安装。因此，这是很少的成本效益来安装额外的冷凝器为唯一目的能量效率。然而，在新建筑中安装额外的冷凝器容量可以成本效益。近似的安装成本与变频驱动和湿球的做法冷凝器控制是指在公式23。增量成本（元）= 17 ·增容（MBH）+ 12,000（23）

在添加额外的冷凝器时收益率（IRR）内部收益率图9显示容量时，冷凝器的寿命是20年，能源涨价率是3 ％。内部收益率计算用于安装的50 ％的额外容量，100％，150 ％和200 ％，比7000 MBH基线能力。在这两个位置，内部收益率超过20％加倍聚光能力。因此，增加聚光能力似乎是一个非常有吸引力的选项的新建筑。

图9。返回的安装额外的电容容量内部收益率

红色=增量成本，绿色=每年节约能源成本，回报广场=内部收益率

小结与讨论

本文开发了一种方法，利用数据来校准聚光性能制冷控制系统。此校准冷凝器性能的仿真中使用模型计算所研究的能源使用的系统。该仿真模型是然后用来计算节能三的ECM ：在冷凝器风扇安装变频器，采用湿球的方法策略，提高聚光性能的两个不同的ASHRAE气候区。

重要的结果是：

1．制冷系统的总功耗是强烈依赖于冷凝器大小，性能和控制。

2．对于现有系统，提高了蒸发式冷凝器性能可能是最成本效益的节能措施。目视检

吉林化工学院本科毕业设计（论文）外文翻译

[4] Manske，K.A.，Reindl酒店，D.T.和克莱因2001年S.A.公司。在工业“蒸发式冷凝器的控制制冷系统制冷24 “国际杂志： 676-691。

[5]米切尔，J.W.博朗，J.E.，1998。“设计，分析和空间调节设备的控制和

系统”。威斯康星大学麦迪逊分校。

[6] 标准与技术，2010年全国学院，参考流体热力学和运输属性数（REFPROP）8.0版 [7] 国家可再生能源实验室，2005年，“用户手册TMY3s ”，http://rredc.nrel.gov/solar/old_data/nsrdb/1991-2005/tmy3/ [8] Stoecker，威尔伯特，1998年，工业制冷手册。麦格劳13-