毕业设计外文翻译
毕业论文(设计)外文文献翻译及原文

金融体制、融资约束与投资——来自OECD的实证分析R.SemenovDepartment of Economics,University of Nijmegen,Nijmegen(荷兰内梅亨大学,经济学院)这篇论文考查了OECD的11个国家中现金流量对企业投资的影响.我们发现不同国家之间投资对企业内部可获取资金的敏感性具有显著差异,并且银企之间具有明显的紧密关系的国家的敏感性比银企之间具有公平关系的国家的低.同时,我们发现融资约束与整体金融发展指标不存在关系.我们的结论与资本市场信息和激励问题对企业投资具有重要作用这种观点一致,并且紧密的银企关系会减少这些问题从而增加企业获取外部融资的渠道。
一、引言各个国家的企业在显著不同的金融体制下运行。
金融发展水平的差别(例如,相对GDP的信用额度和相对GDP的相应股票市场的资本化程度),在所有者和管理者关系、企业和债权人的模式中,企业控制的市场活动水平可以很好地被记录.在完美资本市场,对于具有正的净现值投资机会的企业将一直获得资金。
然而,经济理论表明市场摩擦,诸如信息不对称和激励问题会使获得外部资本更加昂贵,并且具有盈利投资机会的企业不一定能够获取所需资本.这表明融资要素,例如内部产生资金数量、新债务和权益的可得性,共同决定了企业的投资决策.现今已经有大量考查外部资金可得性对投资决策的影响的实证资料(可参考,例如Fazzari(1998)、 Hoshi(1991)、 Chapman(1996)、Samuel(1998)).大多数研究结果表明金融变量例如现金流量有助于解释企业的投资水平。
这项研究结果解释表明企业投资受限于外部资金的可得性。
很多模型强调运行正常的金融中介和金融市场有助于改善信息不对称和交易成本,减缓不对称问题,从而促使储蓄资金投着长期和高回报的项目,并且提高资源的有效配置(参看Levine(1997)的评论文章)。
因而我们预期用于更加发达的金融体制的国家的企业将更容易获得外部融资.几位学者已经指出建立企业和金融中介机构可进一步缓解金融市场摩擦。
毕业设计外文翻译译文

1 工程概论1.1 工程专业1.2 工业和技术1.3 现代制造业工程专业1 工程行业是历史上最古老的行业之一。
如果没有在广阔工程领域中应用的那些技术,我们现在的文明绝不会前进。
第一位把岩石凿削成箭和矛的工具匠是现代机械工程师的鼻祖。
那些发现地球上的金属并找到冶炼和使用金属的方法的工匠们是采矿和冶金工程师的先祖。
那些发明了灌溉系统并建造了远古世纪非凡的建筑物的技师是他们那个时代的土木工程师。
2 工程一般被定义为理论科学的实际应用,例如物理和数学。
许多早期的工程设计分支不是基于科学而是经验信息,这些经验信息取决于观察和经历,而不是理论知识。
这是一个倾斜面实际应用的例子,虽然这个概念没有被确切的理解,但是它可以被量化或者数字化的表达出来。
3 从16、17世纪当代初期,量化就已经成为科学知识大爆炸的首要原因之一。
另外一个重要因素是实验法验证理论的发展。
量化包含了把来源于实验的数据和信息转变成确切的数学术语。
这更加强调了数学是现代工程学的语言。
4 从19世纪开始,它的结果的实际而科学的应用已经逐步上升。
机械工程师现在有精确的能力去计算来源于许多不同机构之间错综复杂的相互作用的机械优势。
他拥有能一起工作的既新型又强硬的材料和巨大的新能源。
工业革命开始于使用水和蒸汽一起工作。
从此使用电、汽油和其他能源作动力的机器变得如此广泛以至于它们承担了世界上很大比例的工作。
5 科学知识迅速膨胀的结果之一就是科学和工程专业的数量的增加。
到19世纪末不仅机械、土木、矿业、冶金工程被建立而且更新的化学和电气工程专业出现了。
这种膨胀现象一直持续到现在。
我们现在拥有了核能、石油、航天航空空间以及电气工程等。
每种工程领域之内都有细分。
6 例如,土木工程自身领域之内有如下细分:涉及永久性结构的建筑工程、涉及水或其他液体流动与控制系统的水利工程、涉及供水、净化、排水系统的研究的环境工程。
机械工程主要的细分是工业工程,它涉及的是错综复杂的机械系统,这些系统是工业上的,而非单独的机器。
毕业设计外文翻译英文加中文传送带

A Comparison of Soft Start Mechanisms for Mining BeltConveyors1800 Washington Road Pittsburgh, PA 15241 Belt Conveyors are an important method for transportation of bulk materials in the mining industry. The control of the application of the starting torque from the belt drive system to the belt fabric affects the performance, life cost, and reliability of the conveyor. This paper examines applications of each starting method within the coal mining industry.INTRODUCTIONThe force required to move a belt conveyor must be transmitted by the drive pulley via friction between the drive pulley and the belt fabric. In order to transmit power there must be a difference in the belt tension as it approaches and leaves the drive pulley. These conditions are true for steady state running, starting, and stopping. Traditionally, belt designs are based on static calculations of running forces. Since starting and stopping are not examined in detail, safety factors are applied to static loadings (Harrison, 1987). This paper will primarily address the starting or acceleration duty of the conveyor. The belt designer must control starting acceleration to prevent excessive tension in the belt fabric and forces in the belt drive system (Suttees, 1986). High acceleration forces can adversely affect the belt fabric, belt splices, drive pulleys, idler pulleys, shafts, bearings, speed reducers, and couplings. Uncontrolled acceleration forces can cause belt conveyor system performance problems with vertical curves, excessive belt take-up movement, loss of drive pulley friction, spillage of materials, and festooning of the belt fabric. The belt designer is confronted with two problems, The belt drive system must produce a minimum torque powerful enough to start the conveyor, and controlled such that the acceleration forces are within safe limits. Smooth starting of the conveyor can be accomplished by the use of drive torque control equipment, either mechanical or electrical, or a combination of the two (CEM, 1979).SOFT START MECHANISM EVALUATION CRITERIONWhat is the best belt conveyor drive system? The answer depends on many variables. The best system is one that provides acceptable control for starting, running, and stopping at a reasonable cost and with high reliability (Lewdly and Sugarcane, 1978). Belt Drive System For the purposes of this paper we will assume that belt conveyors are almost always driven byelectrical prime movers (Goodyear Tire and Rubber, 1982). The belt "drive system" shall consist of multiple components including the electrical prime mover, the electrical motor starter with control system, the motor coupling, the speed reducer, the low speed coupling, the belt drive pulley, and the pulley brake or hold back (Cur, 1986). It is important that the belt designer examine the applicability of each system component to the particular application. For the purpose of this paper, we will assume that all drive system components are located in the fresh air, non-permissible, areas of the mine, or in non-hazardous, National Electrical Code, Article 500 explosion-proof, areas of the surface of the mine.Belt Drive Component Attributes SizeCertain drive components are available and practical in different size ranges. For this discussion, we will assume that belt drive systems range from fractional horsepower to multiples of thousands of horsepower. Small drive systems are often below 50 horsepower. Medium systems range from 50 to 1000 horsepower. Large systems can be considered above 1000 horsepower. Division of sizes into these groups is entirely arbitrary. Care must be taken to resist the temptation to over motor or under motor a belt flight to enhance standardization. An over motored drive results in poor efficiency and the potential for high torques, while an under motored drive could result in destructive overspending on regeneration, or overheating with shortened motor life (Lords, et al., 1978).Torque ControlBelt designers try to limit the starting torque to no more than 150% of the running torque (CEMA, 1979; Goodyear, 1982). The limit on the applied starting torque is often the limit of rating of the belt carcass, belt splice, pulley lagging, or shaft deflections. On larger belts and belts with optimized sized components, torque limits of 110% through 125% are common (Elberton, 1986). In addition to a torque limit, the belt starter may be required to limit torque increments that would stretch belting and cause traveling waves. An ideal starting control system would apply a pretension torque to the belt at rest up to the point of breakaway, or movement of the entire belt, then a torque equal to the movement requirements of the belt with load plus a constant torque to accelerate the inertia of the system components from rest to final running speed. This would minimize system transient forces and belt stretch (Shultz, 1992). Different drive systems exhibit varying ability to control the application of torques to the belt at rest and at different speeds. Also, the conveyor itself exhibits two extremes of loading. An empty belt normally presents the smallest required torque for breakaway and acceleration, while a fully loaded belt presents the highest required torque. A mining drive system must be capable of scaling the applied torque from a 2/1 ratio for a horizontal simple belt arrangement, to a 10/1 ranges for an inclined or complex belt profile.Thermal RatingDuring starting and running, each drive system may dissipate waste heat. The waste heat may be liberated in the electrical motor, the electrical controls,, the couplings, the speed reducer, or the belt braking system. The thermal load of each start Is dependent on the amount of belt load and the duration of the start. The designer must fulfill the application requirements for repeated starts after running the conveyor at full load. Typical mining belt starting duties vary from 3 to 10 starts per hour equally spaced, or 2 to 4 starts in succession. Repeated starting may require the dreading or over sizing of system components. There is a direct relationship between thermal rating for repeated starts and costs. Variable Speed. Some belt drive systems are suitable for controlling the starting torque and speed, but only run at constant speed. Some belt applications would require a drive system capable of running for extended periods at less than full speed. This is useful when the drive load must be shared with other drives, the belt is used as a process feeder for rate control of the conveyed material, the belt speed is optimized for the haulage rate, the belt is used at slower speeds to transport men or materials, or the belt is run a slow inspection or inching speed for maintenance purposes (Hager, 1991). The variable speed belt drive will require a control system based on some algorithm to regulate operating speed. Regeneration or Overhauling Load. Some belt profiles present the potential for overhauling loads where the belt system supplies energy to the drive system. Not all drive systems have the ability to accept regenerated energy from the load. Some drives can accept energy from the load and return it to the power line for use by other loads. Other drives accept energy from the load and dissipate it into designated dynamic or mechanical braking elements. Some belt profiles switch from motoring to regeneration during operation. Can the drive system accept regenerated energy of a certain magnitude for the application? Does the drive system have to control or modulate the amount of retarding force during overhauling? Does the overhauling occur when running and starting? Maintenance and Supporting Systems. Each drive system will require periodic preventative maintenance. Replaceable items would include motor brushes, bearings, brake pads, dissipation resistors, oils, and cooling water. If the drive system is conservatively engineered and operated, the lower stress on consumables will result in lower maintenance costs. Some drives require supporting systems such as circulating oil for lubrication, cooling air or water, environmental dust filtering, or computer instrumentation. The maintenance of the supporting systems can affect the reliability of the drive system.CostThe drive designer will examine the cost of each drive system. The total cost is the sum of the first capital cost to acquire the drive, the cost to install and commission the drive, thecost to operate the drive, and the cost to maintain the drive. The cost for power to operate the drive may vary widely with different locations. The designer strives to meet all system performance requirements at lowest total cost. Often more than one drive system may satisfy all system performance criterions at competitive costs.ComplexityThe preferred drive arrangement is the simplest, such as a single motor driving through a single head pulley.However,mechanical, economic,and functional requirements often necessitate the use of complex drives.The belt designer must balance the need for sophistication against the problems that accompany complex systems. Complex systems require additional design engineering for successful deployment. An often-overlooked cost in a complex system is the cost of training onsite personnel, or the cost of downtime as a result of insufficient training.SOFT START DRIVE CONTROL LOGICEach drive system will require a control system to regulate the starting mechanism. The most common type of control used on smaller to medium sized drives with simple profiles is termed "Open Loop Acceleration Control". In open loop, the control system is previously configured to sequence the starting mechanism in a prescribed manner, usually based on time. In open loop control, drive-operating parameters such as current, torque, or speed do not influence sequence operation. This method presumes that the control designer has adequately modeled drive system performance on the conveyor. For larger or more complex belts, "Closed Loop" or "Feedback" control may he utilized. In closed loop control, during starting, the control system monitors via sensors drive operating parameters such as current level of the motor, speed of the belt, or force on the belt, and modifies the starting sequence to control, limit, or optimize one or wore parameters. Closed loop control systems modify the starting applied force between an empty and fully loaded conveyor. The constants in the mathematical model related to the measured variable versus the system drive response are termed the tuning constants. These constants must be properly adjusted for successful application to each conveyor. The most common schemes for closed loop control of conveyor starts are tachometer feedback for speed control and load cell force or drive force feedback for torque control. On some complex systems, It is desirable to have the closed loop control system adjust itself for various encountered conveyor conditions. This is termed "Adaptive Control". These extremes can involve vast variations in loadings, temperature of the belting, location of the loading on the profile, or multiple drive options on the conveyor. There are three commonadaptive methods. The first involves decisions made before the start, or 'Restart Conditioning'. If the control system could know that the belt is empty, it would reduce initial force and lengthen the application of acceleration force to full speed. If the belt is loaded, the control system would apply pretension forces under stall for less time and supply sufficient torque to adequately accelerate the belt in a timely manner. Since the belt only became loaded during previous running by loading the drive, the average drive current can be sampled when running and retained in a first-in-first-out buffer memory that reflects the belt conveyance time. Then at shutdown the FIFO average may be use4 to precondition some open loop and closed loop set points for the next start. The second method involves decisions that are based on drive observations that occur during initial starting or "Motion Proving'. This usually involves a comparison In time of the drive current or force versus the belt speed. if the drive current or force required early in the sequence is low and motion is initiated, the belt must be unloaded. If the drive current or force required is high and motion is slow in starting, the conveyor must be loaded. This decision can be divided in zones and used to modify the middle and finish of the start sequence control. The third method involves a comparison of the belt speed versus time for this start against historical limits of belt acceleration, or 'Acceleration Envelope Monitoring'. At start, the belt speed is measured versus time. This is compared with two limiting belt speed curves that are retained in control system memory. The first curve profiles the empty belt when accelerated, and the second one the fully loaded belt. Thus, if the current speed versus time is lower than the loaded profile, it may indicate that the belt is overloaded, impeded, or drive malfunction. If the current speed versus time is higher than the empty profile, it may indicate a broken belt, coupling, or drive malfunction. In either case, the current start is aborted and an alarm issued.CONCLUSIONThe best belt starting system is one that provides acceptable performance under all belt load Conditions at a reasonable cost with high reliability. No one starting system meets all needs. The belt designer must define the starting system attributes that are required for each belt. In general, the AC induction motor with full voltage starting is confined to small belts with simple profiles. The AC induction motor with reduced voltage SCR starting is the base case mining starter for underground belts from small to medium sizes. With recent improvements, the AC motor with fixed fill fluid couplings is the base case for medium to large conveyors with simple profiles. The Wound Rotor Induction Motor drive is the traditional choice for medium to large belts with repeated starting duty or complex profilesthat require precise torque control. The DC motor drive, Variable Fill Hydrokinetic drive, and the Variable Mechanical Transmission drive compete for application on belts with extreme profiles or variable speed at running requirements. The choice is dependent on location environment, competitive price, operating energy losses, speed response, and user familiarity. AC Variable Frequency drive and Brush less DC applications are limited to small to medium sized belts that require precise speed control due to higher present costs and complexity. However, with continuing competitive and technical improvements, the use of synthesized waveform electronic drives will expand.REFERENCES[1]Michael L. Nave, P.E.1989.CONSOL Inc.煤矿业带式输送机几种软起动方式的比较1800 年华盛顿路匹兹堡, PA 15241带式运送机是采矿工业运输大批原料的重要方法。
毕业设计论文外文文献翻译

毕业设计(论文)外文文献翻译院系:财务与会计学院年级专业:201*级财务管理姓名:学号:132148***附件: 财务风险管理【Abstract】Although financial risk has increased significantly in recent years risk and risk management are not contemporary issues。
The result of increasingly global markets is that risk may originate with events thousands of miles away that have nothing to do with the domestic market。
Information is available instantaneously which means that change and subsequent market reactions occur very quickly。
The economic climate and markets can be affected very quickly by changes in exchange rates interest rates and commodity prices。
Counterparties can rapidly become problematic。
As a result it is important to ensure financial risks are identified and managed appropriately. Preparation is a key component of risk management。
【Key Words】Financial risk,Risk management,YieldsI. Financial risks arising1.1What Is Risk1.1.1The concept of riskRisk provides the basis for opportunity. The terms risk and exposure have subtle differences in their meaning. Risk refers to the probability of loss while exposure is the possibility of loss although they are often used interchangeably。
毕业设计外文文献翻译范文

毕业设计外文文献翻译专业学生姓名班级学号指导教师优集学院外文资料名称:Knowledge-Based Engineeri--ng Design Methodology外文资料出处:Int.J.Engng Ed.Vol.16.No.1附件: 1.外文资料翻译译文2.外文原文基于知识工程(KBE)设计方法D. E. CALKINS1.背景复杂系统的发展需要很多工程和管理方面的知识、决策,它要满足很多竞争性的要求。
设计被认为是决定产品最终形态、成本、可靠性、市场接受程度的首要因素。
高级别的工程设计和分析过程(概念设计阶段)特别重要,因为大多数的生命周期成本和整体系统的质量都在这个阶段。
产品成本的压缩最可能发生在产品设计的最初阶段。
整个生命周期阶段大约百分之七十的成本花费在概念设计阶段结束时,缩短设计周期的关键是缩短概念设计阶段,这样同时也减少了工程的重新设计工作量。
工程权衡过程中采用良好的估计和非正式的启发进行概念设计。
传统CAD工具对概念设计阶段的支持非常有限。
有必要,进行涉及多个学科的交流合作来快速进行设计分析(包括性能,成本,可靠性等)。
最后,必须能够管理大量的特定领域的知识。
解决方案是在概念设计阶段包含进更过资源,通过消除重新设计来缩短整个产品的时间。
所有这些因素都主张采取综合设计工具和环境,以在早期的综合设计阶段提供帮助。
这种集成设计工具能够使由不同学科的工程师、设计者在面对复杂的需求和约束时能够对设计意图达成共识。
那个设计工具可以让设计团队研究在更高级别上的更多配置细节。
问题就是架构一个设计工具,以满足所有这些要求。
2.虚拟(数字)原型模型现在需要是一种代表产品设计为得到一将允许一产品的早发展和评价的真实事实上原型的过程的方式。
虚拟样机将取代传统的物理样机,并允许设计工程师,研究“假设”的情况,同时反复更新他们的设计。
真正的虚拟原型,不仅代表形状和形式,即几何形状,它也代表如重量,材料,性能和制造工艺的非几何属性。
本科毕业设计外文文献翻译

(Shear wall st ructural design ofh igh-lev el fr ameworkWu Jiche ngAbstract : In t his pape r the basic c oncepts of man pow er from th e fra me sh ear w all str uc ture, analy sis of the struct ur al des ign of th e c ont ent of t he fr ame she ar wall, in cludi ng the seism ic wa ll she ar spa本科毕业设计外文文献翻译学校代码: 10128学 号:题 目:Shear wall structural design of high-level framework 学生姓名: 学 院:土木工程学院 系 别:建筑工程系 专 业:土木工程专业(建筑工程方向) 班 级:土木08-(5)班 指导教师: (副教授)nratiodesign, and a concretestructure in themost co mmonly usedframe shear wallstructurethedesign of p oints to note.Keywords: concrete; frameshearwall structure;high-risebuildingsThe wall is amodern high-rise buildings is an impo rtant buildingcontent, the size of theframe shear wall must comply with building regulations. The principle is that the largersizebut the thicknessmust besmaller geometric featuresshouldbe presented to the plate,the force is close to cylindrical.The wall shear wa ll structure is a flatcomponent. Itsexposure to the force along the plane level of therole ofshear and moment, must also take intoaccountthe vertical pressure.Operate under thecombined action ofbending moments and axial force andshear forcebythe cantilever deep beam under the action of the force levelto loo kinto the bottom mounted on the basis of. Shearwall isdividedinto a whole walland theassociated shear wall in theactual project,a wholewallfor exampl e, such as generalhousingconstruction in the gableor fish bone structure filmwalls and small openingswall.Coupled Shear walls are connected bythecoupling beam shear wall.Butbecause thegeneralcoupling beamstiffness is less thanthe wall stiffnessof the limbs,so. Walllimb aloneis obvious.The central beam of theinflection pointtopay attentionto thewall pressure than the limits of the limb axis. Will forma shortwide beams,widecolumn wall limbshear wall openings toolarge component atbothen ds with just the domain of variable cross-section ro din the internalforcesunder theactionof many Walllimb inflection point Therefore, the calcula tions and construction shouldAccordingtoapproximate the framestructure to consider.The designof shear walls shouldbe based on the characteristics of avariety ofwall itself,and differentmechanical ch aracteristicsand requirements,wall oftheinternalforcedistribution and failuremodes of specific and comprehensive consideration of the design reinforcement and structural measures. Frame shear wall structure design is to consider the structure of the overall analysis for both directionsofthehorizontal and verticaleffects. Obtain theinternal force is required in accordancewiththe bias or partial pull normal section forcecalculation.The wall structure oftheframe shear wall structural design of the content frame high-rise buildings, in the actual projectintheuse of themost seismic walls have sufficient quantitiesto meet thelimitsof the layer displacement, the location isrelatively flexible. Seismic wall for continuous layout,full-length through.Should bedesigned to avoid the wall mutations in limb length and alignment is notupand down the hole. The sametime.The inside of the hole marginscolumnshould not belessthan300mm inordertoguaranteethelengthof the column as the edgeof the component and constraint edgecomponents.Thebi-direc tional lateral force resisting structural form of vertical andhorizontalwallconnected.Each other as the affinityof the shear wall. For one, two seismic frame she ar walls,even beam highratio should notgreaterthan 5 and a height of not less than400mm.Midline columnand beams,wall midline shouldnotbe greater tha nthe columnwidthof1/4,in order toreduce thetorsional effect of the seismicaction onthecolumn.Otherwisecan be taken tostrengthen thestirrupratio inthe column tomake up.If theshear wall shearspan thanthe big two. Eventhe beamcro ss-height ratiogreaterthan 2.5, then the design pressure of thecut shouldnotmakeabig 0.2. However, if the shearwallshear spanratioof less than two couplingbeams span of less than 2.5, then the shear compres sion ratiois notgreater than 0.15. Theother hand,the bottom ofthe frame shear wallstructure to enhance thedesign should notbe less than200mmand notlessthanstorey 1/16,otherpartsshouldnot be less than 160mm and not less thanstorey 1/20. Aroundthe wall of the frame shear wall structure shouldbe set to the beam or dark beamand the side columntoform a border. Horizontal distributionofshear walls can from the shear effect,this design when building higher longeror framestructure reinforcement should be appropriatelyincreased, especially in the sensitiveparts of the beam position or temperature, stiffnesschange is bestappropriately increased, thenconsideration shouldbe givento the wallverticalreinforcement,because it is mainly from the bending effect, andtake in some multi-storeyshearwall structurereinforcedreinforcement rate -likelessconstrained edgeofthecomponent or components reinforcement of theedge component.References: [1 sad Hayashi,He Yaming. On the shortshear wall high-rise buildingdesign [J].Keyuan, 2008, (O2).高层框架剪力墙结构设计吴继成摘要: 本文从框架剪力墙结构设计的基本概念人手, 分析了框架剪力墙的构造设计内容, 包括抗震墙、剪跨比等的设计, 并出混凝土结构中最常用的框架剪力墙结构设计的注意要点。
毕业设计论文 外文文献翻译

毕业设计(论文)外文参考文献翻译计算机科学与信息工程系系(院)2008 届题目企业即时通Instant Messaging for Enterprises课题类型技术开发课题来源自选学生姓名许帅专业班级 04计算机科学与技术指导老师王占中职称工程师完成日期:2008年4 月 6 日目录I NSTANT M ESSAGING FOR E NTERPRISE (1)1. Tips (1)2. Introduction (1)3. First things first (2)4.The While-Accept loop (4)5. Per-Thread class (6)6. The Client class (7)企业即时通 (9)1.提示 (9)2.简介 (9)3.首先第一件事 (10)4.监听循环 (11)5.单线程类 (13)6.用户端类 (14)Instant Messaging for Enterprise1. TipsIf Java is, in fact, yet another computer programming language, you may question why it is so important and why it is being promoted as a revolutionary step in computer programming. The answer isn’t immediately obvious if you’re coming from a tr aditional programming perspective. Although Java is very useful for solving traditional standalone programming problems, it is also important because it will solve programming problems on the World Wide Web. What is the Web?The Web can seem a bit of a mys tery at first, with all this talk of “surfing,”“presence,” and “home pages.” It’s helpful to step back and see what it really is, but to do this you must understand client/server systems, another aspect of computing that is full of confusing issues. The primary idea of a client/server system is that you have a central repository of information,some kind of data, often in a database。
毕业设计(论文)外文资料翻译(学生用)

毕业设计外文资料翻译学院:信息科学与工程学院专业:软件工程姓名: XXXXX学号: XXXXXXXXX外文出处: Think In Java (用外文写)附件: 1.外文资料翻译译文;2.外文原文。
附件1:外文资料翻译译文网络编程历史上的网络编程都倾向于困难、复杂,而且极易出错。
程序员必须掌握与网络有关的大量细节,有时甚至要对硬件有深刻的认识。
一般地,我们需要理解连网协议中不同的“层”(Layer)。
而且对于每个连网库,一般都包含了数量众多的函数,分别涉及信息块的连接、打包和拆包;这些块的来回运输;以及握手等等。
这是一项令人痛苦的工作。
但是,连网本身的概念并不是很难。
我们想获得位于其他地方某台机器上的信息,并把它们移到这儿;或者相反。
这与读写文件非常相似,只是文件存在于远程机器上,而且远程机器有权决定如何处理我们请求或者发送的数据。
Java最出色的一个地方就是它的“无痛苦连网”概念。
有关连网的基层细节已被尽可能地提取出去,并隐藏在JVM以及Java的本机安装系统里进行控制。
我们使用的编程模型是一个文件的模型;事实上,网络连接(一个“套接字”)已被封装到系统对象里,所以可象对其他数据流那样采用同样的方法调用。
除此以外,在我们处理另一个连网问题——同时控制多个网络连接——的时候,Java内建的多线程机制也是十分方便的。
本章将用一系列易懂的例子解释Java的连网支持。
15.1 机器的标识当然,为了分辨来自别处的一台机器,以及为了保证自己连接的是希望的那台机器,必须有一种机制能独一无二地标识出网络内的每台机器。
早期网络只解决了如何在本地网络环境中为机器提供唯一的名字。
但Java面向的是整个因特网,这要求用一种机制对来自世界各地的机器进行标识。
为达到这个目的,我们采用了IP(互联网地址)的概念。
IP以两种形式存在着:(1) 大家最熟悉的DNS(域名服务)形式。
我自己的域名是。
所以假定我在自己的域内有一台名为Opus的计算机,它的域名就可以是。
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南京邮电大学通达学院毕业设计(论文)外文资料翻译学院:计算机工程学院专业:计算机科学与技术学生姓名:王青-_-________班级学号:12006715________外文出处:数据流分析和java服务器页面测试刘鸿渐计算机科学与信息工程系台湾国立台北科技大学抽象Web应用程序通常依赖于服务器端的脚本来处理HTTP请求,生成动态内容与其他组件进行交互。
服务器端的脚本通常与HTML语句混合,很难理解和测试。
特别是,这些脚本没有任何编译检查,可能容易出错,因此,测试服务器端脚本以确保Web应用程序的质量和可靠性变得至关重要。
在本文中,我们在java服务器页面(JSP)中采用传统的数据流测试技术。
java技术是一种非常流行的,用来开发Web 应用程序的服务器端脚本。
我们指出,JSP隐含对象和动作标签可以引入一些需要被处理的数据流测试工件。
测试模型提出捕捉JSP页面的数据流信息的各种隐含对象和动作标记的注意事项。
基于测试模型,我们描述一种方法来计算揭示JSP页面过程内的数据异常和过程间数据流测试路径。
1.介绍Web应用程序迅速扩展到社会的各个领域,如政府、商业、教育和工业。
与其他软件一样,Web应用程序必须进行彻底的测试,以确保其正确性,并符合软件需求。
随着web 应用程序的发展给予了广泛关注,然而,尽可能多的关注给了Web应用程序的开发,存在于Web应用程序测试的报道非常少,网络应用程序仍然在专案过程中测试,许多领域的网络应用程序测试仍然未开发。
最近,一些方法已被提出以解决Web应用程序测试。
大部分的办法集中于在页面级恢复Web应用程序的架构,以提供测试的路线图行使网页和他们的关系。
但是传统的结构测试仍然是web应用程序所必需的,以用来提供足够的代码覆盖率。
因此,在文本中,我们的目标是在数据流分析和JSP页面测试做出努力,让其在Java技术的Web应用程序中起到至关重要的作用。
JSP页面已被广泛用于开发web应用程序来处理HTTP请求,用java组件如java bean 的交互,并生成动态页面。
确保JSP页面被正确写入以及它们与其它组件的交互得到妥善处理是很重要的。
然而,JSP页面通常混淆脚本(即JSP 脚本)以及HTML报表生成动态网页,这使得JSP页面难以理解和测试。
此外,作为一种脚本语言,JSP页面没用任何编译器检查,因此很容易出错。
虽然已有几个测试工具测试JSP页面,比如HttpUnit,,JSP页面测试被认为是困难的,测试用例仍然在专案过程中,最重要的是,JSP页面都引入了一套类似XML标签和隐式对象的动作。
当JSP页面内的程序逻辑是行使使用传统的数据流测试技术时,这些动作标记和隐式模式对象可以提出一些问题。
在本文中,我们通过JSP页面介绍识别和分析可能的数据流测试工件,一种测试模型提供了抽象各种JSP隐含对象和动作标签的数据流信息,用于计算涉及隐含对象和动作标签的数据流测试路径的方法描述和说明。
本论文的主要内容如下:第2节简要回顾了现有的网络应用程序测试方法。
第3节描述了数据流测试工件提出JSP隐式对象和动作标签。
第4节提出了数据流测试模型来表示这些JSP测试工件。
第5节说明了计算JSP页面的过程内和过程间数据流信息的方法。
最后部分总结了结论,并描述了未来的研究方向。
2.相关工作最近,更多的网络应用程序测试的方法已经被提出,Yang et al.[13]拓展传统软件测试架构以支持网络应用测试。
开发一套工具,以帮助分析文件,开发测试用例,执行测试,监控故障,并支持测试测量。
Kung et al.[6,7]在对象和关系方面,提出了一个非结构化网页应用的测试模型。
他们把HTML文档作为对象,并分析与Web应用程序的其他组件及其可能的数据流的相互作用。
数据流测试策略提出从内部对象,对象间的和客户端之间选择测试路径。
Ricca和Tonella[10]描述一种捕获网页,表单,框架的分析模型和它们之间的关系。
该模型提取静态和动态Web应用程序的Web页。
从模型中,测试用例可以推导出测试数据流的网页。
Lucca et al.[8]提出了一个复杂的测试模型来表示一个Web应用程序的基于模型的各种实体,根据他们的模型,提出了一种策略,为生成单元和集成测试的网络应用程序生成初步测试案例。
Wu and Offutt[14]用一个页面的原子量来描述结构静态和动态页面的组合技术和若干规则。
基于用户的交互,他们仅仅测试用例的静态页面和原子元素组成的序列。
Benedikl et al.[1]提出一种自动化的测试过程的Web应用程序的工具,基本上,该工具可以生成测试输入并且能自动探索网站的静态和动态页面。
除了用于测试Web应用程序的功能的方法,Kallepalli and tian[5]and Tonella and Ricca[11]利用Web应用程序在执行过程中收集使用信息和故障日志,来支持可靠性分析,与此同时,Elbaumal.[3]利用Web应用程序捕获数据比采用白盒技术生成用例测试费用少。
3.JSP页面的数据流测试工件数据流测试主要研究变量及其潜在用途的定义为探索程序的数据异常,一个变量的问题可分为C-Use(计算使用)或p-Use(判定使用)。
测试程序的路径是基于定义使用链的选取(或定义使用链),其中一个变量的定义- 使用链是使用自定义的变量,没有任何重新定义的路径介入。
探索JSP页面的数据异常,我们需要考虑的不仅是由JSP技术推出的jsp页面的变量而且还要考虑隐含对象和动作标签。
隐含对象,比如请求和响应对象,允许JSP开发人员访问JSP-provided服务和资源,而无需显式声明的对象。
特别是,一些隐含对象具有控制输入/输出JSP 页面的流量功能。
例如,请求对象,相同的请求对象可以提供给该服务给定的HTTP请求的所有JSP页面。
这会导致JSP页面之间的数据交互。
此外,响应对象的sendRedirect()方法允许HTTP请求重定向到另一个JSP页面,重定向不但可以影响数据在JSP页面中的流动,而且还可以引入两个JSP页面之间或JSP页面和一个Java servlet之间的数据交互。
除了隐含对象,在JSP技术引入了一组标准的类似XML的动作标签,如such as<jsp:useBean>and<jsp:forward>动作标签的代码处理程序,允许JSP页面与其他JSP 页面和Java对象交互关联。
例如,看图1第五行login.jsp页面,有一个<jsp:useBean>标签分配一个标记属性测试Java对象testBean。
该测试属性在第8行作testBean对象的引用参考,其中,变量的数据登录和密码从login.jsp页面传递给test.verify()方法。
结果是,<jsp:useBean>标签需要考虑当捕捉JSP页面和Java对象之间的数据交互时,计算JSP页面的数据流信息。
此外,在图1中的12行,<jsp:forward>标签允许HTTP请求传送带参数my_mum 到debug:jsp页面。
<jsp:forward>标签不仅改变login.jsp页面的流量,而且还导致的login.jsp和debug.jsp页面之间的数据交互。
注意,不同于传统的函数调用,简单的把<jsp:forward>标签从login.jsp页面到debug.jsp页面执行没有任何回调的控制权。
这样的单向数据流必须考虑使JSP页面的数据流信息可正确计算。
图1.JSP动作标签数据交互的一个例子。
表1总结了JSP隐含对象和动作标记几个基本的数据流测试工件的介绍。
应当指出除了<jsp:forward>标签,<jsp:include>的标签允许数据参数传递给另一个JSP页面或Java servlet 于是可以引入JSP页面和servlet之间的数据交互。
虽然,<jsp:include>标签仅包括来自其他JSP 页面和Servlet到当前JSP页面的输出。
控制流是类似于传统函数调用,并且将返回到当前JSP 页面。
4.数据流量测试模型的JSP页面从控制结构的观点来看,JSP页面更像是传统的方法,而不是对象类尽管一个JSP 页面可以包含多个脚本功能。
原因是,一个JSP页面只有一个入口点,并且JSP页面中定义的所有功能只能在JSP页面中进行访问。
因此,对于抽象JSP页面的数据流信息,我们通常考虑JSP页面的传统程序和捕捉他们的过程内和过程间数据流测试工件。
为了表示对JSP页面间数据流信息,控制流图(CFG)注明DEF/USE信息采用。
定义使用注释的CFG是一个有向图。
节点代表JSP脚本语句块的边缘,代表语句块之间的执行流程。
特别是,CFG注释发生变量,隐式对象和利益行为的标签需要注意的是,在第3节所述,response.sendRedirect(),pageContext.forward()和<jsp:forward>标签可以构成一个单向数据流。
因此,该过程内测试模型可能不是一个单入单出射CFG。
此外,在JSP页面中的HTML报表作为报表输出的变量没有任何定义或使用。
另外,每个动作标记块,包括开始标签,零个或多个标签属性,标签体,和结束标记,表示为CFG 单块。
图2示出图1中的注解的CFG为login.jsp页面的清晰度/使用。
定义和变量的用途,隐式对象,和动作标记在对应边注解。
值得注意的,在图1的12行,从开始的所有语句的<jsp:forward>标记,并在结束</ JSP:forward>标记都被认为是的<jsp:forward>的一个XML块标记。
此块是由CFG.In添加节点12表示,“end”节点在CFG cereated由于<jsp:forward> tag.AT 这个节点,控制流从login.jsp页面转移到debug.jsp页面而不回报,过程间的数据流可以被引入。
在这一节点,控制流从login.jsp页面到debug.jsp页面转移没有返回,并可以引入数据流。
2,DEF/USE注释的login.jsp的CFG。
表示涉及一个以上功能或一种JSP页面的数据流的信息,用高清注释过程间控制流图(ICFG)/使用信息所采用的数据流信息,该ICFG已被用于在传统节目的交互功能间数据流模型[4,12]。
为了捕捉JSP页面和Java组件之间的间数据流,CFG的建设要考虑到除了隐式对象和动作标记的功能。
以下列表中的几种情况,其中间数据流可能发生和ICFGs需要建设相应的JSP页面和Java组件。
“main”脚本函数或JSP页面的脚本函数调用同一个JSP页面中的另一个脚本函数。