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机械 中英文 外文翻译 5000

机械 中英文 外文翻译 5000

A web-based manufacturing service systemfor rapid product developmentHongbo Lan a, Yucheng Ding a,*, Jun Hong a, Hailiang Huang b, Bingheng Lu aAbstractThis paper proposes a novel integrated system of rapid product development based on rapid prototyping, and develops anetworked manufacturing service system which offers better support for the rapid product development in small and mediumsized enterprises by taking full advantage of the quickly evolving computer network and information technologies. The architecture of the networked manufacturing service system is presented. Furthermore, some of the key issues, includingmodelling and planning a manufacturing chain, selecting feasible collaborative manufacturers, queuing a manufacturing task, using the sync hronously collaborative work environment, and constructing a suitable running platform, are described in detail. Java-enabled solution, together with web techniques, is employed for building such a networked service system. Finally, an actual example is provided illustrating the application of this service system.Keywords:Rapid product development; Rapid prototyping; Service system; Web-based application1. IntroductionThis is the era of information technology. Informationtechnology has influenced every realm of society, and dramatically impacted on the traditional industry.Current industries are facing the new challenges:quick response to business opportunity has been consideredas one of the most important factors to ensurecompany competitiveness; manufacturing industry isevolving toward digitalization, network and globalization.In order to respond to the change effectively,manufacturing strategy has to be modified from timeto time in accordance with the market situation andcustomer demand. Any change of strategy should enable manufacturers to be better equipped themselves,with capabilities to cope with demands suchas a faster response to market changes, a shortenedlead time of production, improved quality and speed,the ability to deliver quality products to global customers,and improved communications and transportationsystem [1]. It is an established fact that the useof computers in design and manufacturing constitutesthe most significant opportunity for substantial productivitygain in industry. It has now been widelyaccepted that the future of manufacturing organizationswill be information-oriented, knowledge drivenand much of their daily operations will be automatedaround the global information network that connectseveryone together [2]. In order to meet the demand ofrapid product development, various new technologiessuch as reverse engineering (RE), rapid prototyping (RP), and rapid tooling (RT) have emerged and areregarded as enabling tools with abilities to shorten theproduct development and manufacturing time. Forexample, it has been claimed that RP can cut newproduct development costs by up to 70% and the timeto market by 90% [3]. However, these equipments aretoo expensive for the small and medium sized enterprises(SMEs), and many techniques such as 3D CADsolid modelling,RP process planning, free-form surfacesreconstruction, etc., require the high skilled personnelto complete. Therefore, it is especially difficultfor the SMEs to take full advantage of these technologiesin the product development process. In order tooffer the support of rapid product development fornumerousSMEs,manyRPservice bureaus (SBs)whichcan not only manufacture physical prototype and rapidtooling but also provide other engineering services,have been established. By 2001, there are more than500 SBs all over the world. But not every SB canpossess all design and manufacturing capabilitiesrequired, it must employ effectively the externalresource to better satisfy client requirements. Namely,a virtual enterprise which usually defined as a temporaryalliance of enterprises that come together to sharetheir skills, core competencies, and resource in order tobetter respond to business opportunities, whose cooperationis supported by computer networks [4–6], is tobe founded. Every SBconducts only the tasks of its corecompetencies, and depends on numerous partners tocarry out the remaining tasks that this SB has no such manufacturing capabilities to accomplish in time.While a new thought emphasizing service quality is becoming a basic strategy by which manufacturing industries can win global competition in the 21st century. Teleservice engineering is an emerging fieldwhichaddresses ‘‘service’’ issue for manufacturers and customers. As digital manufacturing technique progresses quickly, digital service will be integrated seamlessly into the digital design and manufacturing system [7]. The internet, incorporating computers and multimedia, has provided tremendous potential for remote integration and collaboration in business and manufacturing applications. In order to provide a production collaborative environment for many SMEs and SBs to implement the networked manufacturing, it is especially urgent for many SBs and SMEs to construct a service platform of networked manufacturing to speed up the product development process of the SMEs.The rest of this paper is organized as follows.Related research work is reviewed in Section 2. In Section 3, we introduce an integrated system of rapid product development based on RP. Section 4 describes the workflow and functional design of the networked manufacturing service system. The configuration of system running platform is presented in Section 5. In Section 6, we discuss the design of internet application. A case study is demonstrated in Section 7. Finally, Section 8 concludes the paper.2. Related researchWith the development of computer network and information technologies, the networked manufacturing techniques are playing a more and more important role in manufacturing industry. Substantial investments have been made to support the research and practice of networked manufacturing (telemanufacturing or global manufacturing) from both the academi c community and industrial bodies all over the world in recent years. A number of strategies and frameworks have been proposed. Abdel-Malek et al. [8] described a structure within which a company can outsource several of its production and design activities via internet and developed a model to aid a company in selecting among the available technological and functional alternatives to maximize its flexibility. Montreuil et al. [9] presented a strategi c framework for designing and operating agile manufacturing networks, enabling to collaboratively plan, control and manage day-to-day contingencies in a dynamic environment. Tso et al. [10] introduced the architecture of an agent-based collaborative service support system, which is able to carry out service requests in a manufacturing information networkthrough some specially designed virtual agents. Cheng et al. [11]put forward an integrated framework for web-based design and manufacturing which is developed based on Java solution and CORBA-ORG broking technologies. Offodile and Abdel-Malek [12] introduced a framework for integrating IT and manufacturing strategies using the virtual manufacturing paradigm. Huang et al. [13] presented a holonic framework for virtual enterprises and control mechanisms of virtual enterprises under this framework. O’Sullivan [14]described an information architecture and associated toolset for understanding and managing the process of business development. Akkermansa and Horstc [15] discussed managerial aspects of information technology infrastructure standardisation in networked manufacturing firms and presented a strategic framework to guide managers in making sensible decisions regarding IT infrastructure standardisation, based on a number of pre-existing economic and management theories, such as transaction cost theory, organisational design and IT maturity growth stages. Jin et al. [16] presented a research on key application technologies and solutions, which includes a network safety strategy which ensures data transfer among the leaguer members; production data management based on Web/DOT (distributed object technology) and XML criteria which ensure data exchange in structure-variance characteristic environments; the network platform which provides the conversion service of different types of CAD files. Woerner and Woern [17] introduced a new web service based platform providing developed methods for co-operative plant production within virtual engineering.To full realize the teleservice engineering in today’s globalized manufacturing industry and meet the current market situation and customer demand, a number of global manufacturing networks have been established by, among others, the Society of Manufacturing Engineer [18], Lockheed Martin (AIMSNET) [19] and 3M (the 3M Innovation Global Network) [20].Today’s industries are facing serious structural problems brought about by their rapid development of overseas activities under a global integrated manufacturing environment. Service and maintenance are becoming extremely important practices for companies to maintain their manufacturing productivity and customer satisfaction in foreign regions. Due to the inherent problems of traditional help desk support, some companies have started developing web-based online customer service support system. Foo et al. [21]described an integrated help desk support for customer service via internet. Lee [7] discussed the concept and framework of a teleservice engineering system for the life cycle support of manufacturing equipment and products. A system for remote customer support has been created in the FCSA demonstrator of the Globerman 21 project [22]. The purpose of these systems above is to provide effective and responsive remote support to customers in the use, maintenance and troubleshooting of their equipment.University of California is studying and developing a project called the Tele-Manufacturing Facility (TMF) which is to create an automated RP capability on the Internet. TMF allows users to easily submit jobs and have the system automatically maintain a queue. While it can automatically check many flaws in .STL files, and in many cases, fix them [23]. RP potentially offers great benefits when used during the design and manufacturing process. However, RP must be used in an effective manner if these benefits are to be fully exploited. The RP-novices have a lot of difficulties in getting a global view of the RP technique and in tackling well founded decision for investment or outsourcing of RP tasks because of the very quick appearance of new and improved processes in this field. In order to help novices select asuitable RP process, the rapid prototyping system selector has been developed by many researchers [24–27]. Quickparts. com, which is a privately held manufacturing services company dedicated to providing customers with an on-line E-commerce system to procure lowvolume and high-volume custom manufactured parts, has developed a QuickQuote system. The QuickQuote system enables customers to get instant, customerized quotations for the production of their parts [28]. 3D Systems Company, which is the earliest and biggest RP equipment manufacturer, has provided RP&M service for customer via Internet [29].From these literatures survey, it is clear that most of studies mainly focused on the strategy and overall architecture of networked manufacturing as well as individual function module, there is still no comprehensive and banausic networked manufacturing service system to support rapid product development. Built on the emerging researches and our earlier work (e.g. Refs. [30,31]), a web-based manufacturing service system for rapid product development is to be established.3. Architecture of the integrated system ofrapid product developmentThe development process from initial conceptual design to commercial product is an iterative process which includes: product design; analysis of performance, safety and reliability; product prototyping for experimental evaluation; and design modification. Therefore, any step of new product development process has a direct and strong influence on time-to-market. A good product development system must enable designers or design teams to consider all aspects of product design, manufacturing, selling and recycling at the early stage of a design cycle. So that design iteration and changes can be made easily and effectively. The more fluent the feedback is, the higher possibility success of the system has. Design for manufacturing (DFM) and concurrent engineering (CE) require that product and process design be developed simultaneously rather than sequentially [32].The integrated system of rapid product development is composed of three modules: digital prototype, physical prototype and rapid tooling and functional part manufacturing system. The product development starts from the creation of a 3D model using a 3D CAD software package. At that stage the product geometry is defined and its aesthetic and dimensional characteristics are verified. The main function of digital prototype is to perform 3D CAD modelling. The product and its components are directly designed on a 3D CAD system (e.g. Pro/Engineer, Unigraphics, CATIA, IDEAS, etc.) during the creative design process. If a physical part is available, the model can be constructed by the reverse engineering (RE) technique. RE is a methodology for constructing CAD models of physical parts by digitizing an existing part, creating a digital model and then using it to manufacturing components [33]. RE can reduce the development cycle when redesigns become necessary for improved product performance. Pre-existing parts with features for improved performance can be readily incorporated into the desired part design. When a designer creates a new design using mock-up, it is also necessary to construct the CAD model of the mock-up for further use of the design data in analysis and manufacturing. The three primary steps in RE process are part digitization, features extraction, and 3D CAD modelling. Part digitization is accomplished by a variety of contact or non-contact digitizers. There are various commercial systems available for part digitization. There systemsrange from coordinate measuring machine (CMM), laser scanners to ultrasonic digitizers. They can be classified into two broad categories: contact and non-contact. Laser triangulation scanner (LTS), magnetic resonance images (MRI), and computer tomography (CT) are commonly used non-contact devices. Contact digitizers mainly have CMM and cross-sectional imaging measurement (CIM). Feature extraction is normally achieved by segmenting the digitized data and capturing surface features such as edges. Part modelling is fulfilled through fitting a variety of surface to the segmented data points [34]. In order to reduce the iterations of design-prototypetest cycles, increase the product process and manufacturing reliability, it is necessary to guide in optimization of the product design and manufacturing process through CAE.The CAD model can be directly converted to the physical prototype using a RP technique. RP is a new forming process which fabricates physical parts layer by layer under computer control directly from 3D CAD models in a very short time. In contrast to traditional machining methods, the majority of rapid prototyping systems tend to fabricate parts based on additive manufacturing process, rather than subtraction or removal of material. Therefore, this type of fabrication is unconstrained by the limitations inherent in conventional machining approaches [35]. RP potentially offers great benefits when used during the design and manufacturing process. It can help shorten time-to-market, improve quality and reduce cost. Over the last 10 years, RP machines have been widely used in industry. The RP methods commercially available include Stereolithgraphy (SL), Selective Laser Sintering (SLS), Fused Deposition Manufacturing (FDM), Laminated Object Manufacturing (LOM), Ballistic Particle Manufacturing (BMP), and Three Dimensional Printing (3D printing) [36], etc.RTis a technique that transforms the RP patterns into functional parts, especially metal parts. Furthermore, the integration of both RP and RT in development strategy promotes the implementation of concurrent engineering in companies. Numerous processes have been developed for producing dies fromRP system. The RT methods can generally be divided into direct and indirect tooling categories, and also soft (firm) and hard tooling subgroups. Indirect RT requires some kinds of master patterns, which can be made by conventional methods (e.g. HSM), or more commonly by an RP process such as SL or SLS. Direct RT, as the name suggests, involves manufacturing a tool cavity directly on the RP system, hence eliminating the intermediatestep of generating a pattern [37]. On the basis of abovetechniques, a novel integrated system of rapid product development is to be established. Its detailed structure is shown in Fig. 1.4. The workflow and function designThe workflow of the service system of networkedmanufacturing is shown in Fig. 2. The first step is to log in to the website of SB. Users have to enter their names and passwords. Those without registration or authorization can also enter into the system, but they are limited to viewing the information that is open to the public such as ‘‘typical cases’’ in this system. The password entered by the user will be verified by the system. After entering the SB website successfully, the system will check the security level of users, and determine which modules they can access or employ. According to authentication for the system, all usersa re to be divided into four categories: general users (without registration), potential clients, real clients, and system administrator. Received job requests from clients, the SB will perform firstly process planning which fulfills the task decomposition and selects the most suitable process methods. It is necessary for users to get the preliminary product quote and manufacturing time from the SB before the follow-up process continues. If such results may be accepted initially, The SB will negotiate further with users by Video-conferencing system. Once come to term each other, a contract is to be confirmed, and the user becomes a real client. The manufacturing tasks submitted by real clients had better be implemented in the SB. However, if the SB has no such manufacturing capabilities or can not accomplish then in time, it is an effective way thatthe SB takes full advantage of external sources to carry out the remaining tasks.The next step is to select the appropriate collaborative manufacturing enterprises to form a virtual enterprise to complete the tasks by the task assignment decision system. In addition, in order to monitor the manufacturing schedule to ensure smooth production, both collaborative manufacturing enterprises and SB itself must provide as quickly as possible the essential information related to production progress and schedule for the module of production monitor. So any companies falling behind schedule or failing to meet quality standards will be closely examined by SB and users to ensure that precautionary or remedial measures are made ahead of time or any damaging effects are predicted.Referring to the workflow of networked service system above and the functional requirement of the digital teleservice system, the service system consists of nine functional modules: the technique research, typical cases, information consultation, ASP (application service provider) tool set, client management,Electronic commerce, manufacturing service, system navigation. Its detailed structure is shown in Fig. 3.These nine components work together seamlessly to achieve the common objectives, i.e. to provide an effective and prompt service platform to support the rapid product development of SMEs. One of the purposes of the technique research is to enable users to increase awareness of the relevant knowledge of rapid product development. In order to help users better understand and apply these new techniques, the system illustrates a number of real-life cases. Both thetechnique research and typical cases mainly provide self-help service for users. Depending on the predominance of specialty and expert, the SB can answer the queries of clients and communicate with novices to solve their problems by the information consultation module. The ASP tool set provides five useful components below: the process planning of RE/RP/RT, STL checking and fixing, the optimization of part orientation, the support structure generation, and the optimization of part slicing. There are various process methods for RE, RP and RT as previously described, each of them has its characteristics and the scope of application. It is especially difficult for many novices to select the most suitable process methods according to the individual task requirement and condition. Three selectors based on ASP mode, namely, ‘‘RE selector’’, ‘‘RP selector’’, and ‘‘RT selector’’ have been developed to perform process planning automatically in the Web Serverside. In [38], Miller states that .STL files created from solid models have anomalies about 10% of the time and those created from surface models have problems about 90%of the time. Error rates in this range make it clear that automated error checking is important for all RP operations. Based on our experience with supplying network-based resources, we know that it is especially crucial to perform automatic error checking when the RP operation is not at the designer’s sit e. We have developed various algorithms to detect, and in some cases, automatically fix geometric and topological flaws. There are two ‘‘firewalls’’ to detect those flaws: one is integrated with the online pricing engine that will be operated by the user before the .STL file is submitted to the SB, while the other is to run on the SB’s Server-side after the .STL file is submitted. Because the function of fixing is quite restricted, if a .STL file has fatal flaws or loses some data during transferring, it would have to be uploaded again from the Client-side. Parts formed using RP technique can vary significantly in quality depending on the manufacturing process planning. The process planning of RP is performed to generate the tool paths and process parameters for a part that is to be built by a particular RP process. The steps required are the part orientation, support structure generation, slicing, path planning, and process parameter selection. Therefore, it is also very important for remote users that SB can provide these process planning techniques. Three sub-modules including the optimization of part orientation, support structure generation, and the optimization of part slicing, have been developed to aid effectively users in setting RP process variables in order to best achieve specific build goals and desired part characteristic. Both potential clients and real clients can employ freely the ASP tool set.Electronic commerce module is composed of foursections: the online quote, build-time estimation, online business negotiation, and electronic contract management. Conventionally, the SB may quote according to the client’s offerings (e.g. CAD models, 2D drawings or physical prototypes) utilizing their experiences or just get payment after the RP model has been built. But for teleservice, it is necessary for the remote users to inquire about the service expense of making RP prototype before the follow-up process continues. Hence, an online pricing engine (OPE) has been developed. The details of the OPE Stereolithography oriented have been discussed in [39]. The accurate prediction of the build-time required is also critical for various activities such as: the job quoting, the job scheduling, the selection of build parameters (e.g. layer thickness and orientation), benchmarking, etc. Two build-time estimators based on sliced process and STL have been exploited, respectively. Ref. [40]presents the principle of a build-time estimation algorithm for Stereolithograpy based on model geometrical features. After clients accept initially the quote, they may negotiate with SB on the business andtechnological details. The Microsoft NetMeeting which can set up a collaborative environment to fulfill information sharing, file transferring, Video and Audio communication etc., provides an ideal tool for the online negotiation. It is also seamlessly integrated IE Browser, thus clients can call SB at any moment. As a result of negotiation, an electronic contract is to be signed. To effectively manage andoperate these electronic contracts, the system alsoprovides a contract management component. It is especially convenient and prompt for clients to submit, inquire, and search contract through this module.The manufacturing service module which covers the job management, collaborat ive manufacturing, process monitor, and collaborative enterprises management, is regarded as one of the most important function modules in the service system. When a contract is confirmed, clients will formally submit their job requirements (e.g. RE, 3D CAD modelling, CAE, RP prototype, or rapid tooling) and sources (e.g. object parts, digitized data cloud, 2D models, 3D models, or .STL files). In order to help many novices submit quickly and easy the manufacturing tasks, various job and source templates have been created, while the client can search, modify, and even delete the manufacturing tasks itself if the occasion arises. The Collaborative Manufacturing System (CMS) is responsible for the selection of collaborative enterprises (CE). In addition, it is extraordinarily important and necessary to monitor the manufacturing schedule and control product quality to ensure smooth production. In the past, a SB had to spend much time on dealing with a lot of inquires from the clients by via phone calls or Faxes. Now, the Process Monitor System (PMS) provides various facilities which canguarantee the tasks to be completed timely. Any partners falling behind schedule or failing to meet quality standards will be closely examined by SB and users to ensure that precautionary or remedial measures are made ahead of time or any damaging effects are predicted.All information (no matter if it is a real client being ready for a contract with the SB or just a potential one showing his intent or inquiry) involved in the whole service process are managed and maintained by a special Database. These data provide strong supports for both online business and manufacturing service. To create a collaborative environment among SB, users and CE, we have to rely fully on the multimedia and Internet. Therefore, the service system offers three enabling tools: Video conferencing system, Electronic white-boarding, and FTP. In order to make use of the system as quickly as possible, users can get help from the system navigation module. These nine components form a fully-integrated system that is able to carry out tasks in an efficient and effective way.On the basis of the workflow and function module of service system, the system framework can be constructed as shown in Fig. 4. Fig. 5 illustrates the networked structure of service system.5. Configuration of running platformIn order to run this system effectively, constructing asuitable running platform is necessary and especially crucial. An operating system (OS) is one of the most basic software components for running this system. The operating systems commonly founded onWeb Servers are UNIX, OS, Linux, and Windows, etc. Windows 2000 Advanced Server is a better platform for running business application. Better SMP scalability, improved networking performance, and support for more physical memory have a profound impact on the performance of Windows 2000 Advanced Server in an application server environment. Hence, we select Windows 2000 Advanced Server as the operating systemof the running platform. Web Servers including Apache, IIS, iPlanet, CERN, and IBM WebSphere, are frequently installed websites at the present time. Internet Information Services (IIS) 5.0 which is integratedWindows Advanced 2000 Server is a new release Web Server of Microsoft Company. Not only being a Server, it also provides a number of other Internet services such as FTP, News, WWW, and SMTP, etc. With tighter integration between the operating system and IIS, it offers performance gains and higher availability for Web Servers and sites. Normally IIS can not execute Servlet and Java Server Pages (JSP), configuring IIS to use Tomcat redirector plugin will let IIS send Servlet, and JSP requests to Tomcat (and thisway, serve them to clients). Tomcat3.2 of the Apache Software Foundation is selected to act as the engine of JSP and Servlets. Database Server adopts SQL Server 2000 Relational Database. Exchange Server 5.5 is to be used to implement the mail service function. In order to prevent hacking system, two firewalls based on package filtration and proxy Server, namely, Cisico2511 router and Proxy Server 2.0, have been established. The overall configuration of Web platform is shown in Table 1.。

毕业论文 翻译材料(中英)

毕业论文 翻译材料(中英)

原文Sometimes it becomes apparent that previous approaches to a problem haven’t quite worked the way you anticipated.Perhaps you just need to clear away the smoky residue of the past,take a deep breath,and try again with a new attitude and fresh ideas. In golf,it’s known as a“mulligan”;in schoolyard sports,it’s called a “do-over”;and in the computer industry,we say it’s a“reboot.”A reboot is what Microsoft has initiated with its new approach to the mobile phone market.With its clean look,striking fonts,and new organizational paradigms, Microsoft Windows Phone7not only represents a break with the Windows Mobile past but also differentiates itself from other smartphones currently in the market. Windows Phone7devices will be made by several manufacturers and available with a variety of cell providers.For programmers,Windows Phone7is also exciting,for it supports two popular and modern programming platforms:Silverlight and XNA.Silverlight—a spinoff of the client-based Windows Presentation Foundation (WPF)—has already given Web programmers unprecedented power to develop sophisticated user interfaces with a mix of traditional controls,high-quality text, vector graphics,media,animation,and data binding that run on multiple platforms and browsers.Windows Phone7extends Silverlight to mobile devices.XNA—the three letters stand for something like“XNA is Not an Acronym”—is Microsoft’s game platform supporting both2D sprite-based and3D graphics with a traditional game-loop architecture.Although XNA is mostly associated with writing games for the Xbox360console,developers can also use XNA to target the PC itself, as well as Microsoft’s classy audio player,the Zune HD.Either Silverlight or XNA would make good sense as the sole application platform for the Windows Phone7,but programmers have a choice.And this we call“an embarrassment of riches.”Targeting Windows Phone7All programs for Windows Phone7are written managed code.Although the sample programs in this book are written in the C#programming language,it is also possible to write Windows Phone7applications in Visual .The free downloadable Microsoft Visual Studio2010Express for Windows Phone includes XNA Game Studio4.0 and an on-screen phone emulator,and also integrates with Visual Studio2010.You can develop visuals and animations for Silverlight applications using Microsoft Expression Blend.2The Silverlight and XNA platforms for Windows Phone7share some libraries,and you can use some XNA libraries in a Silverlight program and vice versa.But you can’t create a program that mixes visuals from both platforms.Maybe that will be possible in the future,but not now.Before you create a Visual Studio project,you must decide whether your million-dollar idea is a Silverlight program or an XNA program. Generally you’ll choose Silverlight for writing programs you might classify as applications or utilities.These programs are built from a combination of markup and code.The markup is the Extensible Application Markup Language,or XAML andpronounced“zammel.”The XAML mostly defines a layout of user-interface controls and panels.Code-behind files can also perform some initialization and logic,but are generally relegated to handling events from the controls.Silverlight is great for bringing to the Windows Phone the style of Rich Internet Applications(RIA), including media and the Web.Silverlight for Windows Phone is a version of Silverlight3excluding some features not appropriate for the phone,but compensating with some enhancements.XNA is primarily for writing high-performance games.For2D games,you define sprites and backgrounds based around bitmaps;for3D games you define models in3D space. The action of the game,which includes moving graphical objects around the screen and polling for user input,is synchronized by the built-in XNA game loop.The differentiation between Silverlight-based applications and XNA-based games is convenient but not restrictive.You can certainly use Silverlight for writing games and you can even write traditional applications using XNA,although doing so might sometimes be challenging.In particular,Silverlight might be ideal for games that are less graphically oriented,or use vector graphics rather than bitmap graphics,or are paced by user-time rather than clock-time.A Tetris-type program might work quite well in Silverlight.You’ll probably find XNA to be a bit harder to stretch into Silverlight territory,however.Implementing a list box in XNA might be considered“fun”by some programmers but a torture by many others.The first several chapters in this book describe Silverlight and XNA together,and then the book splits into different parts for the two platforms.I suspect that some developers will stick with either Silverlight or XNA exclusively and won’t even bother learning the other environment.I hope that’s not a common attitude.The good news is that Silverlight and XNA are so dissimilar that you can probably bounce back and forth between them without confusion!Microsoft has been positioning Silverlight as the front end or“face”of the cloud, so cloud services and Windows Azure form an important part of Windows Phone7 development.The Windows Phone is“cloud-ready.”Programs are location-aware and have access to maps and other data through Bing and Windows Live.One of the available cloud services is Xbox Live,3which allows XNA-based programs to participate in online multiplayer games,and can also be accessed by Silverlight applications.Programs you write for the Windows Phone7will be sold and deployed through the Windows Phone Marketplace,which provides registration services and certifies that programs meet minimum standards of reliability,efficiency,and good behavior. I’ve characterized Windows Phone7as representing a severe break with the past. If you compare it with past versions of Windows Mobile,that is certainly true.But the support of Silverlight,XNA,and C#are not breaks with the past,but a balance of continuity and innovation.As young as they are,Silverlight and XNA have already proven themselves as powerful and popular platforms.Many skilled programmers are already working with either one framework or the other—probably not so many withboth just yet—and they have expressed their enthusiasm with a wealth of online information and communities.C#has become the favorite language of many programmers (myself included),and developers can use C#to share libraries between their Silverlight and XNA programs as well as programs for environments. The Hardware ChassisDevelopers with experience targeting Windows Mobile devices of the past will find significant changes in Microsoft’s strategy for the Windows Phone7.Microsoft has been extremely proactive in defining the hardware specification,often referred to as a“chassis.”Initial releases of Windows Phone7devices will have one consistent screen size.(A second screen size is expected in the future.)Many other hardware features are guaranteed to exist on each device.The front of the phone consists of a multi-touch display and three hardware buttons generally positioned in a row below the display.From left to right,these buttons are called Back,Start,and Search:•Back Programs can use this button for their own navigation needs,much like the Back button on a Web browser.From the home page of a program,the button causes the program to terminate.•Start This button takes the user to the start screen of the phone;it is otherwise inaccessible to programs running on the phone.4•Search The operating system uses this button to initiate a search feature.The initial releases of Windows Phone7devices have a display size of480×800 pixels.In the future,screens of320×480pixels are also expected.There are no other screen options for Windows Phone7,so obviously these two screen sizes play a very important role in phone development.In theory,it’s usually considered best to write programs that adapt themselves to any screen size,but that’s not always possible,particularly with game development.You will probably find yourself specifically targeting these two screen sizes,even to the extent of having conditional code paths and different XAML files for layout that is size-dependent.I will generally refer to these two sizes as the“large”screen and the “small“screen.The greatest common denominator of the horizontal and vertical dimensions of both screens is160,so you can visualize the two screens as multiples of160-pixel squares:480320480800I’m showing these screens in portrait mode because that’s usually the way smartphones are designed.The screen of the original Zune is240×320pixels;the Zune HD is272×480.Of course,phones can be rotated to put the screen into landscape mode.Some programs might require the phone to be held in a certain orientation;others might be moreadaptable.You have complete control over the extent to which you support orientation.By default,Silverlight applications appear in portrait mode,but you’ll probably want to write your Silverlight applications so they adjust themselves to orientation changes.New events are available specifically for the purpose of detecting orientation change,and some orientation shifts are handled automatically.In contrast,game programmers can usually impose a particular orientation on the user. XNA programs use landscape mode by default,but it’s easy to override that.5In portrait mode,the small screen is half of an old VGA screen(that is,640×480).In landscape mode,the large screen has a dimension sometimes called WVGA (“wide VGA”).In landscape mode,the small screen has an aspect ratio of3:2or 1.5;the large screen has an aspect ratio of5:3or1.66….Neither of these matches the aspect ratio of television,which for standard definition is4:3or1.33…and for high-definition is16:9or1.77….The Zune HD screen has an aspect ratio of 16:9.Like many recent phones and the Zune HD,the Windows Phone7displays will likely use OLED(“organic light emitting diode”)technology,although this isn’t a hardware requirement.OLEDs are different from flat displays of the past in that power consumption is proportional to the light emitted from the display.For example, an OLED display consumes less than half the power of an LCD display of the same size, but only when the screen is mostly black.For an all-white screen,an OLED consumes more than three times the power of an LCD.Because battery life is extremely important on mobile devices,this characteristic of OLED displays implies an aesthetic of mostly black backgrounds with sparse graphics and light-stroked fonts.Regardless,Windows Phone7users can choose between two major color themes:light text on a dark background,or dark text on a light background.Most user input to a Windows Phone7program will come through multi-touch.The screens incorporate capacitance-touch technology,which means that they respond to a human fingertip but not to a stylus or other forms of pressure.Windows Phone7 screens are required to respond to at least four simultaneous touch-points.A hardware keyboard is optional.Keep in mind that phones can be designed in different ways,so when the keyboard is in use,the screen might be in either portrait mode or landscape mode.A Silverlight program that uses keyboard input must respond to orientation changes so that the user can both view the screen and use the keyboard without wondering what idiot designed the program sideways.An on-screen keyboard is also provided,known in Windows circles as the Soft Input Panel or SIP.XNA programs also have access to the hardware keyboard and SIP.译文有时候以前的方法显然无法达到预期效果,这时也许需要告别迷雾茫茫的过去。

驱动桥5000字外文翻译文献

驱动桥5000字外文翻译文献

As the bearing cage rotates, read the value7. indicated on the scale.Preload normally is specified as torque re-8. quired to rotate the pinion bearing cage, so take a reading only when the cage is rotating. Starting torque will give a false reading.To calculate the preload torque, measure the 9. diameter of the bearing cage where the cord was wound. Divide this dimension in half to get the radius.10. U se the following procedure to calculate thebearing preload torque:Standard.Pull (lb) 3 radius (inches) 5 preload (lb-in.)orPreload (lb-in.) 3 0.113 (a conversion constant) 5 preload (N .m)Install the yoke, flat washer, and nut. Tighten 6. the nut snugly. Tap the end of the input shaft lightly to seat the bearings.Measure the input shaft endplay again with 7. the dial indicator. If endplay is still incorrect, repeat steps 3 through 7.With the endplay correct, seal the shim pack 8. to prevent lube leakage. Then torque the i nput shaft nut and cover capscrews to the correct value.24.5 A XLE ADJUSTMENTSAND CHECKSThis section introduces the differential carrier adjust-ments, checks, and tests that the truck technician must be capable of performing; some have beenr eferred to previously in the text. For the most part, the procedures described here are general in nature. The truck technician should refer to OEM servicel iterature for specific procedures.PINION BEARING PRELOADMost differential carriers are provided with a press-fit outer bearing on the drive pinion gear. Some older rear drive axles use an outer bearing, which slips over the drive pinion. The procedures for adjusting both types follow.Press-Fit Method AdjustmentTo adjust the pinion bearing preload using the press-fit method, use the following procedure:Assemble the pinion bearing cage, bearings, 1. spacer, and spacer washer (without drive pin-ion or oil seal). Center the bearing spacer and spacer washer between the two bearing cones (Figure 24–49).When a new gear set or pinion bearings are 2. used, select a nominal size spacer based on OEM specifications. If original parts are used, use a spacer removed during disassembly of the drive.Place the drive pinion and cage assembly in a 3. press, with the gear teeth toward the bottom.Apply and hold the press load to the pinion 4. bearing. As pressure is applied, rotate the bearing cage several times so that the bear-ings make normal contact.While pressure is held against the assembly, wind 5. a cord around the bearing cage several times.Attach a spring scale to the end of the cord 6. (Figure 24–50). Pull the cord with the scale ona horizontal line.FIGURE 24–49 Assembly of the pinion bearing cage.(Courtesy of Dana Corporation)FIGURE 24–50 Cage in press to check bearingp reload.Sleeve must applymust be against the outer bearing. If the fit between the yoke or flange splines and drive pinion splines is tight, use a press to install the yoke or flange (Figure 24–51).Temporarily install the drive pinion and cage 4. assembly in the carrier (Figure 24–52). Do not install shims under the bearing cage.Install the bearing cage to the carrier cap-5. screws. Washers are not required at this time. Hand-tighten the capscrews.Fasten a yoke or flange bar to the yoke or 6. flange (Figure 24–53). The bar will hold the drive pinion in position when the nut ist ightened.Metric.Pull (kg) 3 radius (cm) 5 preload (kg-cm) orPreload (kg-cm) 3 0.098 (a conversion constant) 5 preload (N .m)Examples. We can convert the foregoing equa-tions into examples by applying some data to them:Standard7.5 lb 3 3.31 in. 5 24.8 lb-in. (preload) or24.8 lb-in. 3 0.113 5 2.8 N .m (preload)Metric3.4 kg 3 8.4 cm 5 28.6 kg-cm (preload) or28.6 kg-cm 3 0.098 5 2.8 N .m (preload)11. I f necessary, adjust the pinion bearing preloadby changing the pinion bearing spacer. A thicker spacer will decrease preload, whereas a thinner spacer will increase the preload.12. O nce the correct bearing preload has beenestablished, note the spacer size used. Select a spacer 0.001 inch (0.025 mm) larger for use in the final pinion bearing cage assembly pro-cedures. The larger spacer compensates for slight expansion of the bearing, which occurs when pressed on the pinion shank. The trial spacer pack should result in correct pinion bearing preload in three times out of four cases.Y oke Method of AdjustmentTo adjust the pinion bearing preload using the yoke or flange method, proceed as follows:Assemble the complete pinion bearing cage 1. as recommended in the press-fit method.A forward axle pinion is equipped with a heli-2. cal gear. For easier disassembly during bear-ing adjustment procedures, use a dummy yoke (if available) in place of the helical gear.Install the input yoke or flange, nut, and 3.washer on the drive pinion. The yoke or flangeFIGURE 24–51 Using a press to install the yoke orflange to the drive pinion. (Courtesy of Arvin Meritor)FIGURE 24–52 Install the pinion and cage assembly in the carrier housing. (Courtesy of Arvin Meritor)indicated on the torque wrench (see Figure 24–55). Typical value is 50 lb-ft. (68 N .m)m aximum applied to one side gear.If the torque value exceeds the specification, 5. disassemble the differential gears from the case halves.Check the case halves, spider, gears, and 6. thrust washers for the problem that caused the torque value to exceed specifications. Re-pair or replace defective parts as required. Remove any foreign debris.Check/Adjust Pinion Cage Shim PackThis procedure is used to check and adjust the thick-ness of the shim pack used in the pinion bearing cage. Use this procedure if a new drive pinion and crownTighten the nut on the drive pinion to specifi-7. cation, typically 400 to 700 lb-ft. (542 to 950 N .m).Remove the yoke or flange bar.8. Attach a torque wrench to the drive pinion 9. nut. Rotate the drive pinion and read the value indicated on the torque wrench. Preload is correct when the torque required to rotate the pinion bearing cage is from 15 to 35 lb-in. (1.7 to 4.0 N .m).To adjust the pinion bearing preload, disas-10. semble the pinion bearing cage and change the pinion bearing spacer size. A thicker spacer will decrease preload, whereas a thin-ner spacer will increase preload.Differential Rolling ResistanceA check to measure and establish differential rolling resistance follows. To perform this check, a special tool must be made. You can easily make this tool from an old axle shaft that matches the spline size of the differential side gear. Figure 24–54 illustrates the fab-rication specifications for this special tool.To check differential resistance to rotation, use the following procedure:Install soft metal covers over the vise jaws to 1. protect the ring gear (Figure 24–55).Place the differential and crown gear assem-2. bly in the vise.Install the special tool into the differential until 3. the splines of the tool and one side gear are engaged.Attach a torque wrench to the nut of the spe-4. cial tool and rotate the differential gears. As the differential gears rotate, read the valueFIGURE 24–55 Reading the torque value to check the rolling resistance. (Courtesy of Arvin Meritor)FIGURE 24–53 Using a flange bar to hold the drivepinion in position. (Courtesy of Arvin Meritor)FIGURE 24–54 Fabrication details for a tool to checkthe rolling resistance. (Courtesy of Arvin Meritor)If the new pinion cone number is a minus (–), sub-8. tract the number from the standard shim packthickness that was calculated in step 3 or 4.The value calculated in step 7 or 8 is the 9.t hickness of the new shim pack that will bei nstalled. Figure 24–59 illustrates several e xamples of determining shim pack t hickness.Install the drive pinion, bearing cage, and new10. shim pack into the differential carrier.gear set is to be installed, or if the depth of the drive pinion has to be adjusted. You are checking the rolling resistance using a torque wrench.To check/adjust the shim pack thickness (Figure 24–56), do the following:With a micrometer, measure the thickness of 1. the old shim pack removed from under the pinion cage (Figure 24–57). Record the mea-surement for later use.Look at the pinion cone (PC) variation number 2. on the drive pinion being replaced (Figure 24–58). Record this number for later use also.If the old pinion cone number is a plus (+), 3. subtract the number from the old shim pack thickness that was recorded in step 1.If the old pinion cone number is a minus (–), 4. add the number to the old shim thickness that was measured in step 1.The value calculated in step 3 or 4 is the 5.t hickness of the standard shim pack without variation.Look at the PC variation number on the new 6. drive pinion that will be installed. Record the number for later use.If the new pinion cone number is a plus (+), 7. add the number to the standard shim packthickness that was calculated in step 3 or 4.FIGURE 24–56 Drive pinion depth controlled by shimpack thickness. (Courtesy of Arvin Meritor)FIGURE 24–57 Measuring the thickness of the old shim pack. Mike each shim individually then add tocalculate total thickness. (Courtesy of Arvin Meritor)FIGURE 24–58 Location of the pinion cone (PC)v ariation number. (Courtesy of Arvin Meritor)Adjust Differential Bearing PreloadOne of two methods can be used to check and adjust the preload of the differential bearings.Method One.Attach a dial indicator onto the mounting 1. flange of the carrier and adjust the indicator so that the plunger rides on the back surface of the crown ring gear (Figure 24–60).Loosen the bearing adjusting ring that is op-2. posite the ring gear so that a small amount of endplay is indicated on the dial indicator. To turn the adjusting rings, use a T-bar wrench that engages two or more opposite notches in the ring (Figure 24–61).Move the differential and crown gear to the 3. left and right using prybars as you read the dial indicator. Use two prybars that fit be-tween the bearing adjusting rings and the ends of the differential case (Figure 24–62). You also can use two prybars between the differential case or crown gear and the carrier at locations other than those just described. In either case, the prybars must not touch the differential bearings.EXAMPLES:Inchesmm 1.Old Shim Pack Thickness Old PC Number, PC +2Standard Shim Pack Thickness New PC Number, PC +5New Shim Pack Thickness .030.76–.002–.05.028.71+.005+.13.033.842.Old Shim Pack Thickness Old PC Number, PC –2Standard Shim Pack Thickness New PC Number, PC +5New Shim Pack Thickness .030.76+.002+.05.032.81+.005+.13.037.943.Old Shim Pack Thickness Old PC Number, PC +2Standard Shim Pack Thickness New PC Number, PC –5New Shim Pack Thickness .030.76–.002–.05.028.71–.005–.13.023.584.Old Shim Pack Thickness Old PC Number, PC –2Standard Shim Pack Thickness New PC Number, PC –5New Shim Pack Thickness.030.76+.002+.05.032.81–.005–.13.027.68FIGURE 24–59 Determining shim pack thickness.(Courtesy of ArvinMeritor Inc.)FIGURE 24–60 Dial indicator attached to carrier-mounted flange. (Courtesy of Arvin Meritor)FIGURE 24–61 Turning the adjusting ring using aT-bar wrench. (Courtesy of Arvin Meritor)FIGURE 24–62 Using pry bars to adjust play in the crown gear. (Courtesy of Arvin Meritor)Tighten the same bearing adjusting ring4.so that no endplay shows on the diali ndicator.Move the differential and crown gear to the5.left and right as needed. Repeat step 3 untilzero endplay is achieved.Tighten each bearing adjusting ring one6.notch from the zero endplay measured instep 4.Method Two.A second method of checking pre-load is to measure the expansion between the bearing caps after you tighten the adjusting rings. Use the following procedure:Turn both adjusting rings hand tight against1.the differential bearings.Measure the distance X or Y between oppo-2.site surfaces of the bearing caps (Figure24–63A) using a large micrometer of thec orrect size (Figure 24–63B). Make a note ofthe m easurement.Tighten each bearing adjusting ring one3.notch.Measure the distance X or Y again. Compare4.the dimension with the distance X or Y mea-sured in step 2. The difference between thetwo dimensions is the amount that the bear-ing caps have expanded.Example: Measurements of a carrier.Distance X or Y before tightening adjusting rings5 15.315 inches (389.00 mm)Distance X or Y after tightening adjusting rings5 15.324 inches (389.23 mm)15.324 inches minus 15.315 inches5 0.009 inch (0.23 mm) differenceIf the dimension is less than specification, repeat steps 3 and 4 as needed.Crown Gear Runout CheckTo check the runout of the crown/ring gear, do the f ollowing:Attach a dial indicator on the mounting flange1.of the differential carrier (Figure 24–64).Adjust the dial indicator so that the plunger or2.pointer is against the back surface of thecrown gear.FIGURE 24–63 (A) Location of distances measured to check expansion between bearing caps aftert ightening adjusting rings; (B) measuring this distance.(Courtesy of Arvin Meritor)FIGURE 24–64 Checking crown gear runout. (Courtesy of Arvin Meritor)Pinion and Crown Tooth ContactA djustment Correct tooth contact between the pinion and crown gear cannot be overemphasized, because improper tooth contact results in noisy operation and prema-ture failure. The tooth contact pattern consists of the lengthwise bearing (along the tooth of the ring gear) and the profile bearing (up and down the tooth). F igure 24–68 shows crown gear toothn omenclature.Adjust the dial of the indicator to zero.3. Rotate the differential and crown gear when4. reading the dial indicator. The runout of the crown gear must not exceed 0.008 inch (2 mm) (a typical value; refer to the applicable OEM service literature for the specificv alues).If runout of the crown gear exceeds the speci-5. fication, remove the differential and crown gear assembly from the carrier. Check the dif-ferential components, including the carrier, for the problem causing the runout of the gear to exceed specification. Repair or replace defec-tive components.After the components are repaired or re-6. placed, install the differential and crown gear into the carrier.Repeat the preload adjustment of the 7. differential bearings. Then repeat this runout procedure.Check/Adjust Crown Gear BacklashIf the used crown and pinion gear set is installed, ad-just the backlash to the setting that was measured before the carrier was disassembled. If a new gear set is to be installed, adjust backlash to the correct speci-fication for the new gear set.To check and adjust ring gear backlash, do thef ollowing: Attach a dial indicator onto the mounting1. flange of the carrier (see Figure 24–64).Adjust the dial indicator so that the plunger is 2. against the tooth surface at a right angle.Adjust the dial of the indicator to zero, making 3. sure that the plunger is loaded through at least one revolution.Hold the drive pinion in position.4. When reading the dial indicator, rotate the5. crown gear a small amount in both directions against the teeth of the drive pinion (Figure 24–65). If the backlash reading is not within specification (typically ranging from 0.010 to 0.020 inch or 254 to 508 mm), adjust backlash as outlined in steps 6 and 7.Loosen one bearing adjusting ring one notch 6. and then tighten the opposite ring the same amount. Backlash is increased by moving the crown gear away from the drive pinion (Figure 24–66). Backlash is decreased by moving the crown gear toward the drive pin-ion (Figure 24–67).Repeat steps 2 through 5 until the backlash is 7.within specifications.FIGURE 24–65 Check crown gear backlash. ( Courtesy of Arvin Meritor)FIGURE 24–66 Adjustments to increase backlash. (Courtesy of Arvin Meritor)the pattern in an unloaded condition (such as when you are performing this test) will be approximately one-half to two-thirds of the crown gear tooth in most models and ratios.Checking Tooth Contact Pattern on a Used Gear Set. Used gearing will not usually display the square, even contact pattern found in new gear sets. The gear will normally have a pocket at the toe-end of the gear tooth (Figure 24–71) that tails into a contact line along the root of the tooth. The more use a gear has had, the more the line becomes the dominant characteristic of the pattern.Adjusting Tooth Contact Pattern. When dis-assembling, make a drawing of the gear tooth con-tact pattern so that when reassembling it is possible to replicate approximately the same pattern. A cor-rect pattern should be clear of the toe and centers evenly along the face width between the top land and the root. Otherwise, the length and shape of the pattern can be highly variable and are usually con-sidered acceptable—providing the pattern does not run off the tooth at any time. If necessary, adjust the contact pattern by moving the crown gear and drive pinion.Checking Tooth Contact Pattern on a New Gear Set. Paint 12 crown gear teeth with a marking compound (Figure 24–69) and roll the gear to obtain a tooth contact pattern. A correct pattern should be well centered on the crown gear teeth with lengthwise contact clear of the toe (Figure 24–70). The length ofFIGURE 24–67 Adjustments to decrease backlash.(Courtesy of Arvin Meritor)FIGURE 24–68 Crown gear tooth nomenclature.(Courtesy of Dana Corporation)FIGURE 24–69 Application of a marking compoundto check tooth contact. (Courtesy of Dana Corporation)FIGURE 24–70 Correct tooth contact patternfor new gearing. (Courtesy of Dana Corporation)FIGURE 24–71 Correct tooth contact pattern for used gearing. (Courtesy of Dana Corporation)making adjustments, first adjust the pinion and then the backlash. Continue this sequence until the pattern is satisfactory.Thrust Screw AdjustmentFor those differential carriers equipped with a thrust screw, perform the following procedure. (If the carrier assembly does not have a thrust block, proceed to step 4 of this procedure.)Rotate the carrier in the repair stand until the 1. back surface of the crown gear is toward the top.Put the thrust block on the back surface of 2. the ring gear. The thrust block must be in the center between the outer diameter of the gear and the differential case.Rotate the crown gear until the thrust block 3. and hole for the thrust screw, in the carrier, are aligned.Install the jam nut on the thrust screw, one-4. half the distance between both ends (Figure 24–74).Install the thrust screw into the carrier until the 5. screw stops against the crown gear or thrust block.Loosen the thrust screw one-half turn, or 180 6. degrees.Tighten the jam nut to the correct torque value 7. against the carrier (typical values range from 150 to 295 lb-ft. or 200 to 400 N .m) (Figure 24–75).Axle TrackingAxle tracking can be measured using the older tram bar method or electronic alignment equipment. The procedures for setting axle alignment and tracking areexplained in Chapter 25.FIGURE 24–72 Two incorrect patterns when adjusting pinion position. (Courtesy of Dana Corporation)Crown gear position controls the backlash setting. This adjustment also moves the contact pattern along the face width of the gear tooth (Figure 24–72). Pinion position is determined by the size of the pinion bear-ing cage shim pack. It controls contact on the tooth depth of the gear tooth (Figure 24–73).These adjustments are interrelated. As a result, they must be considered together even though thepattern is altered by two distinct operations. WhenFIGURE 24–73 Two incorrect patterns when adjusting backlash. (Courtesy of Dana Corporation)• Most differential carriers are replaced as rebuilt/exchange units, so the role of the technician is, more often than not, to diagnose the problem and then, if necessary, to replace the defective assembly as a unit.• The technician who has disassembled and reas-sembled differential carriers should find trouble-shooting procedures easier to follow.• Follow the OEM procedure when disassem-bling differential carriers. Taking a few mo-ments to measure shim packs and gear tooth contact patterns on disassembly can save considerable time when reassembling thec arrier.• A crown and pinion gear set often can ber eused when rebuilding a differential carrier. Make sure that you inspect it properly ond isassembly.• Crown and pinion gear sets are always replaced as a matched pair during a rebuild.• When setting crown and pinion backlash, it is increased by moving the crown gear away from the drive pinion and decreased by moving the crown gear toward the drive pinion.• Adhering to OEM-recommended lubrication schedules is the key to ensuring the longest service life from both drive and dead axles.• Knowing the correct procedure to check lubricant level is essential. The level is correct when lubri-cant is exactly level with the bottom of the fill hole.• Because most OEMs approve of the use of syn-thetic lubricants in final drive carriers, lubrication drain schedules have been greatly increased in recent years. Drain schedules are determined by the actual lubricant used and the type of appli-cation to which the vehicle is subjected.• Servicing of axles on heavy-duty trucks consists of routine inspection, lubrication, cleaning, and, when required, troubleshooting and component overhaul.• Failure analysis is required to prevent recurrent failures.• Drive axle carrier components usually fail for one of the following reasons: Shock load Fatigue Spinout Lubrication problemsNormal wearFIGURE 24–74 Installing the jam nut on the thrust screw. (Courtesy of Arvin Meritor)FIGURE 24–75 Tighten the jam nut to the correct torque value. (Courtesy of Arvin Meritor)SUMMARY。

毕业论文5000字英文文献翻译

毕业论文5000字英文文献翻译

英文翻译英语原文:. Introducing ClassesThe only remaining feature we need to understand before solving our bookstore problem is how to write a data structure to represent our transaction data. In C++ we define our own data structure by defining a class. The class mechanism is one of the most important features in C++. In fact, a primary focus of the design of C++ is to make it possible to define class types that behave as naturally as the built-in types themselves. The library types that we've seen already, such as istream and ostream, are all defined as classesthat is,they are not strictly speaking part of the language.Complete understanding of the class mechanism requires mastering a lot of information. Fortunately, it is possible to use a class that someone else has written without knowing how to define a class ourselves. In this section, we'll describe a simple class that we canuse in solving our bookstore problem. We'll implement this class in the subsequent chapters as we learn more about types,expressions, statements, and functionsall of which are used in defining classes.To use a class we need to know three things:What is its name?Where is it defined?What operations does it support?For our bookstore problem, we'll assume that the class is named Sales_item and that it is defined in a header named Sales_item.h.The Sales_item ClassThe purpose of the Sales_item class is to store an ISBN and keep track of the number of copies sold, the revenue, and average sales price for that book. How these data are stored or computed is not our concern. To use a class, we need not know anything about how it is implemented. Instead, what we need to know is what operations the class provides.As we've seen, when we use library facilities such as IO, we must include the associated headers. Similarly, for our own classes, we must make the definitions associated with the class available to the compiler. We do so in much the same way. Typically, we put the class definition into a file. Any program that wants to use our class must include that file.Conventionally, class types are stored in a file with a name that, like the name of a program source file, has two parts: a file name and a file suffix. Usually the file name is the same as the class defined in the header. The suffix usually is .h, but some programmers use .H, .hpp, or .hxx. Compilers usually aren't picky about header file names, but IDEs sometimes are. We'll assume that our class is defined in a file named Sales_item.h.Operations on Sales_item ObjectsEvery class defines a type. The type name is the same as the name of the class. Hence, our Sales_item class defines a type namedSales_item. As with the built-in types, we can define a variable of a class type. When we write "Sales_item item" we are saying that item is an object of type Sales_item. We often contract the phrase "an object of type Sales_item" to"aSales_ item object" or even more simply to "a Sales_item."In addition to being able to define variables of type Sales_item, we can perform the following operations on Sales_item objects:Use the addition operator, +, to add two Sales_items,Use the input operator, << to read a Sales_item object,Use the output operator, >> to write a Sales_item object,Use the assignment operator, =, to assign one Sales_item object to another,Call the same_isbn function to determine if two Sales_items refer to the same book.Classes are central to most C++ programs: Classes let us define our own types that are customizedfor the problems we need to solve, resulting in applications that are easier to write and understand.Well-designed class types can be as easy to use as the built-in types.A class defines data and function members: The data members store the state associated with objectsof the class type, and the functions perform operations that give meaning to the data. Classeslet us separate implementation and interface. The interface specifies the operations that the classsupports. Only the implementor of the class need know or care about the details of the implementation. This separation reduces the bookkeeping aspects that make programming tedious anderror-prone.Class types often are referred to as abstract data types. An abstract data type treats the data(state) and operations on that state as a single unit. We can think abstractly about what the classd oes, rather than always having to be aware of how the class operates. Abstract data types arefundamental to both object-oriented and generic programming.Data abstraction is a programming (and design) technique that relies on the separation of interfaceand implementation. The class designer must worry about how a class is implemented, but programmersthat use the class need not know about these details. Instead, programmers who use a type need to know only the type's interface; they can think abstractly about what the type does rather than concretely about how the type works.Encapsulation is a term that describes the technique of combining lower-level elements to forma new, higher-level entity. A function is one form of encapsulation: The detailed actions performedby the function are encapsulated in the larger entity that is the function itself. Encapsulated elements hide the details of their implementationwe may call a function but have no access to the statements that it executes. In the same way, a class is an encapsulated entity: It represents an aggregation of several members, and most (well-designed) class types hide the members that implement the type.If we think about the library vector type, it is an example of both data abstraction andencapsulation. It is abstract in that to use it, we think about its interfaceabout the operations that it can perform. It is encapsulated because we have no access to the details of how the type is representated nor to any of its implementation artifacts. An array, on the other hand, is similar in concept to a vector but is neither abstract nor encapsulated. We manipulate an array directly by accessing the memory in which the array is stored.Not all types need to be abstract. The library pair class is a good example of a useful, well-designed class that is concrete rather than abstract. A concrete class is a class that exposes, rather than hides, its implementation.Some classes, such as pair, really have no abstract interface. The pair type exists to bundle two data members into a single object. There is no need or advantage to hiding the data members. Hiding the members in a class like pair would only complicate the use of the type.Even so, such types often have member functions. In particular, it is a good idea for any class that has data members of built-in or compound type to define constructor(s) to initialize those members. The user of the class could initialize or assign to the data members but it is less error-prone for the class to do so.Programmers tend to think about the people who will run their applications as "users." Applicationsare designed for and evolve in response to feedback from those who ultimately "use" the applications. Classes are thought of in a similar way: A class designer designs and implements a class for "users" of that class. In this case, the "user" is a programmer, not the ultimate user of the application.Authors of successful applications do a good job of understanding and implementing the needs ofthe application's users. Similarly, well-designed, useful classes are designed with a close attention to the needs of the users of the class.In another way, the division between class designer and class user reflects the division betweenusers of an application and the designers and implementors of the application. Users care only if the application meets their needs in a cost-effective way. Similarly, users of a class care only about its interface. Good class designers define a class interface that is intuitive and easy to use. Users care about the implementation only in so far as the implementation affects their use of the class. If the implementation is too slow or puts burdens on users of the class, then the users must care. In well-designed classes, only the class designer worries about the implementation.In simple applications, the user of a class and the designer of the class might be one and the same person. Even in such cases, it is useful to keep the roles distinct. When designing the interface to a class, the class designer should think about how easy it will be to use the class. When using the class, the designer shouldn't think about how the class works.When referring to a "user," the context makes it clear which kind of user is meant. If we speak of "user code" or the "user" of the Sales_item class, we mean a programmer whois using a class in writing an application. If we speak of the "user" of the bookstore application, we mean the manager of the store who is running the application.Data abstraction and encapsulation provide two important advantages:1.Class internals are protected from inadvertent user-level errors, which might corrupt the state of the object.2.The class implementation may evolve over time in response to changing requirements or bug reports without requiring change in user-level code.By defining data members only in the private section of the class, the class author is free to make changes in the data. If the implementation changes, only the class code needs to be examined to see what affect the change may have. If data are public, then any function that directly accesses the data members of the old representation might be broken. It would be necessary to locate and rewrite all those portions of code that relied on the old pesentation before the program could be used again.Similarly, if the internal state of the class is private, then changes to the member data can happen in only a limited number of places. The data is protected from mistakes that users might introduce. If there is a bug that corrupts the object's state, the places to look for the bug are localized: When data are private, only a member function could be responsible for the error. The search for the mistake is limited, greatly easing the problems of maintenance and program correctness.If the data are private and if the interface to the member functions does not change, then user functions that manipulate class objects require no change.Because changing a class definition in a header file effectively changes the text of every source file that includes that header, code that uses a class must be recompiled when the class changes.Classes are the most fundamental feature in C++. Classes let us define new types that are tailored to our own applications, making our programs shorter and easier to modify.Data abstractionthe ability to define both data and function membersand encapsulationthe ability to protect class members from general accessare fundamental to classes. Member functions define the interface to the class. We encapsulate the class by making the data and functions used by the implementation of a class private.Classes may define constructors, which are special member functions that control how objects of the class are initialized. Constructors may be verloaded. Every constructor should initialize every data member. Constructors should use a constructor initializer list to initialize the data members. Initializer lists are lists of namevalue pairs where the name is a member and the value is an initial value for that member.Classes may grant access to their nonpublic members to other classes or functions. A class grants access by making the class or function a friend.Classes may also define mutable or static members. A mutable member is a data member that is never const; its value may be changed inside a const member function. Astatic member can be either function or data; static members exist independently of the objects of the class type.Copy ControlEach type, whether a built-in or class type, defines the meaning of a (possibly empty) set of operations on objects of that type. We can add two int values, run size on a vector, and so on. These operations define what can be done with objects of the given type.Each type also defines what happens when objects of the type are created. Initialization of objects of class type is defined by constructors. Types also control what happens when objects of the type are copied, assigned, or destroyed. Classes control these actions through special member functions: the copy constructor, the assignment operator, and the destructor. This chapter covers these operations.When we define a new type, we specifyexplicitly or implicitlywhat happens when objects of that type are copied, assigned, and destroyed. We do so by defining special members: the copy constructor, the assignment operator, and the destructor. If we do not explicitly define the copy constructor or the assignment operator, the compiler will (usually) define them for us.The copy constructor is a special constructor that has a single parameter that is a (usually const) reference to the class type. The copy constructor is used explicitly when we define a new object and initialize it from an object of the same type. It is used implicitly when we pass or return objects of that type to or from functions.Collectively, the copy constructor, assignment operator, and destructor are referred to as copy control. The compiler automatically implements these operations, but the class may define its own versions.Copy control is an essential part of defining any C++ class. Programmers new to C++ are often confused by having to define what happens when objects arecopied, assigned, or destroyed. This confusion is compounded because if we do not explicitly define these operations, the compiler defines them for usalthough they might not behave as we intend.Often the compiler-synthesized copy-control functions are finethey do exactly the work that needs to be done. But for some classes, relying on the default definitions leads to disaster. Frequently,the most difficult part of implementing the copy-control operations is recognizing when we need to override the default versions. One especially common case that requires the class to define its own the copy-control members is if the class has a pointer member.The Copy ConstructorThe constructor that takes a single parameter that is a (usually const) reference to an object of the class type itself is called the copy constructor. Like the default constructor, the copy constructor can be implicitly invoked by the compiler. The copy constructor is used to:1.Explicitly or implicitly initialize one object from another of the same type;2.Copy an object to pass it as an argument to a function;3.Copy an object to return it from a function;4.Initialize the elements in a sequential container;5.Initialize elements in an array from a list of element initializers.Forms of Object DefinitionRecall that C++ supports two forms of initialization (Section 2.3.3, p. 48): direct and copy.Copy-initialization uses the = symbol, and direct-initialization places the initializer in parentheses.The copy and direct forms of initialization, when applied to objects of class type, are subtly different. Direct-initialization directly invokes the constructor matched by the arguments. Copy-initialization always involves the copy constructor. Copy-initialization first uses the indicated constructor to create a temporary object (Section 7.3.2, p. 247). It then uses the copy constructor to copy that temporary into the one we are creating: string null_book = "9-999-99999-9"; // copy-initializationstring dots(10, '.'); // direct-initializationstring empty_copy = string(); // copy-initializationstring empty_direct; // direct-initializationFor objects of class type, copy-initialization can be used only when specifying a single argument or when we explicitly build a temporary object to copy.When dots is created, the string constructor that takes a count and a character is called and directly initializes the members in dots. To create null_book, the compiler first creates a temporary by invoking the string constructor that takes a C-style character string parameter. The compiler then uses the string copy constructor to initialize null_book as a copy of that temporary.The initialization of empty_copy and empty_direct both call the string default constructor. In the first case, the default constructor creates a temporary object, which is then used by the copy constructor to initialize empty_copy. In the second case, the default constructor is run directly on empty_direct.The copy form of initialization is primarily supported for compatibility with C usage. When it can do so, the compiler is permitted (but not obligated) to skip the copy constructor and create the object directly.Usually the difference between direct- or copy-initialization is at most a matter of low-level optimization. However, for types that do not support copying, or when using a constructor that is nonexplicit (Section 12.4.4, p. 462) the distinction can be essential: ifstream file1("filename"); // ok: direct initializationifstream file2 = "filename"; // error: copy constructor is private// This initialization is okay only if// the Sales_item(const string&) constructor is not explicitSales_item item = string("9-999-99999-9");The initialization of file1 is fine. The ifstream class defines a constructor that can be called with a C-style string. That constructor is used to initialize file1.The seemingly equivalent initialization of file2 uses copy-initialization. That definition is not okay. We cannot copy objects of the IO types (Section 8.1, p. 287), so we cannot use copy-initialization on objects of these types.Whether the initialization of item is okay depends on which version of our Sales_item class we are using. Some versions define the constructor that takes a string as explicit. If the constructor is explicit, then the initialization fails. If the constructor is not explicit, then the initialization is fine.If a class does not define one or more of these operations, the compiler will define them automatically. The synthesized operations perform memberwise initialization, assignment, or destruction: Taking each member in turn, the synthesized operation does whatever is appropriate to the member's type to copy, assign, or destroy that member. If the member is a class type, the synthesized operation calls the corresponding operation for that class (e.g., the copy constructor calls the member's copy constructor, the destructor calls its destructor, etc.). If the member is a built-in type or a pointer, the member is copied or assigned directly; the destructor does nothing to destroy members of built-in or pointer type. If the member is an array, the elements in the array are copied, assigned, or destroyed in a manner appropriate to the element type.中文译文类的简介解决书店问题之前,还需要弄明白如何编写数据结构来表示交易数据。

论文翻译5000字

论文翻译5000字

Customer delight in a retail context: investigating delightful and terrible shopping experiencesMark J. Arnold, Kristy E. Reynold, NicolePonder, Jason E.LuegAbstract:The concept of delight is of great interest to practitioners who understand that to keep customers loyal, a firm must go beyond merely satisfying to truly delighting them [Bus. Mark. Dig.17 (1992) 17; Mark. News 24 (1990) 10]. However, few studies specifically dedicated to customer delight have surfaced in the marketing literature [J. Retail. 73 (1997) 311], and no research to the authors’ knowledge has explored delight in a retail setting. Therefore, the purpose of this study was to examine customer delight in a retail-shopping context. Specifically, qualitative research was conducted to determine the sources of delightful and terrible shopping experiences for retail shoppers. Critical incident analysis of 113 depth interviews with shoppers revealed several factors associated with delightful or terrible shopping experiences and the resulting consequences from these experiences. A number of strategic implications are discussed, and limitations and directions for future research are also addressed.Keywords: Customer delight; Shopping; Critical incident technique1. IntroductionOver the past decade, practitioners and academics alike have argued that an essential strategy for success and survival in today’s marketplace is the creation and maintenance of satisfied and loyal customers (Parasuraman et al.,1985; Reichheld and Sasser, 1990; Rust and Zahorik, 1992,1993; Zeithaml et al., 1990). Customer satisfaction has been linked to a number of important outcomes, including increasedmarket share, profitability, customer retention and oyalty, purchase intentions, usage rates, and the benefits associated with positive word-of-mouth effects (Anderson and Sullivan, 1993; Anderson et al., 1994; Bitner, 1990; Boulding et al., 1993; Cronin and Taylor, 1992; Fornell and Wernerfelt, 1987, 1988; LaBarbera and Mazursky, 1983;Zeithaml, 2000; Zeithaml et al., 1996). As a result, firms have made significant financial and human resource investments into the measurement and analysis of customer satisfaction and its subsequent improvement (Jones and Sasser, 1995; Oliver, 1999; Reichheld and Sasser, 1990; Rust et al., 1995).However, while evidence of the value of customer satisfaction continues to accumulate, firms are increasingly having difficulty connecting satisfaction efforts to the ‘‘bottom line’’ (Reichheld,1996). For example, a study by the Juran Institute found that fewer than 30% of 200 firms believed that their satisfaction management efforts added to their bottom line, and fewer than 2% were able to measure a bottom-line improvement (Hepworth and Mateus, 1994). Indeed, studies have consistently shown that many customers who switch are often satisfied with their prior brand experience, with overall switching among satisfied customers across many industries approaching 80% (Keaveney, 1995; Oliver, 1999; Reichheld, 1996).In response to these developments, practitioners have suggested that merely attaining satisfaction may be insufficient, and that going beyond customer satisfaction to ‘‘customer delight’’ is required (Schlossberg, 1990). Executives in leading companies often ass ert that customer satisfaction by itself is insufficient for developing long-term loyalty because customers expect to be satisfied in today’s marketplace and simply meeting those expectations is insufficient (Oliver et al., 1997). In other words, customers are satisfied when the company can avoid problems (i.e., the ‘‘zerodefects’’ mentality), but to keep customers for the longrun, companies must do more.For many companies, ‘‘doing more’’ suggests the generationof higher levels of emotion than those associated with mere satisfaction evaluations, and the growing belief amongmany executives is that customers exposed tounexpected, pleasant experiences—those experiences which are delightful—are far more likely to develop into long-term loyalfollowers. Hence, creating delighted customers clearlyrequires new approaches to customer management thanmore traditional satisfaction-building efforts can offer.These developments, in conjunction with equivocal academic research regarding the value of increasing customer satisfaction (Reichheld, 1993), have led to a growing interest among retail firms in creating customer delight asthe basis for long-term customer profitability.In line with these marketplace developments, recent thinking on the part of service quality and s atisfaction researchers has begun to focus on these ‘‘higher levels’’ of satisfaction that may generate exceptional results in the form of unshakable customer loyalty. While customer delight has been thought to be key to true customer loyalty and loyalty-driven profits (Oliver et al., 1997), it remains largely unexplored in academic research. Therefore, before delight can be properly linked to the bottom line, it is imperative that retailers understand the causes of such experiences.Researchers in social psychology have distinguished between delight and lower arousal levels of happiness (de Rivera et al., 1989), and several studies in marketing have addressed emotions in the satisfaction response (Oliver and Westbrook, 1993). However, few studies specifically dedicated to customer delight have appeared (e.g., Oliver et al., 1997; Rust and Oliver, 2000), and no research to the authors’ knowledge has explored delight in a retail setting.Furthermore, although Schneider and Bowen (1999) have addressed customer outrage and others have examined such issues as identifying unfavorable or dissatisfactory service encounters (cf. Bitner et al., 1990, 1994), the research on ‘‘terrible’’ shopping experiences is very limited. Clearly there is a need for such knowledge.Therefore, the purpose of this paper is to examine the concept of customer delight in a retail setting. Specifically, the sources of delightful shopping experiences are explored and compared with sources of terrible shopping experiences to construct a taxonomic framework in which shoppers’ experiences are classified. To investigate these questions, the critical incident technique (CIT; Flanagan, 1954) is employed in an emergent research design. Critical incident approaches have been widely used in prior research investigating service encounters (Bitner et al., 1990, 1994), service quality (Iacobucci et al., 1995), customer switching behavior (Keaveney, 1995), and selfservice technologies (Meuter et al., 2000). This technique is employed here to explore sources and outcomes of delightful and terrible shopping experiences in an attempt to identify broad groupings of factors that influence whatmakes a shopping experience delightful or terrible and also the outcomes of a delightful or terrible shoppingexperience.First, an overview of the literature on customer delight is presented. Following this, the results of a qualitative investigation involving over 100 depth interviews with shoppers are described. Finally, results, limitations, and directions for future research are discussed.2. BackgroundWhile practitioners have realized the importance of delighting customers for some time (cf. Coyne, 1989), only recently has academic research in marketing explored the construct of customer delight. The review of the literature is organized around a discussion of behavioral conceptions of delight, its affective basis, and other important consumer and firm variables that are likely to influence the formation of delight and its outcomes. In addition, the limited amount of research that relates most closely to ‘‘terrible’’ customer experiences—unfavorable or dissatisfying service encounters— is briefly reviewed.2.1. Behavioral conception of delightThe expectancy–disconfirmation model (Oliver, 1980)provides basis for understanding the concept of delight.Within this framework, consumers are thought to compare perceived performance with prior expectations, and if performance exceeds expectations, then a state of positive disconfirmation exists and the customer is satisfied. However, researchers have made the distinction that disconfirmation can vary in terms of its ‘‘unexpectedness’’ (Oliverand Winer, 1987). For example, performance experienced outside a range of experience-based norms can result in three categories of confirming/disconfirming events: confirmed performance, whereslight performance deviations are considered normal; disconfirmed performance which is plausible, but experienced infrequently; and disconfirmed performance which is highly unlikely based on past experience, and hence is unexpected or surprising (Oliver, 1989;Oliver and Winer, 1987; Woodruff et al., 1982). It is thislatter category that has been described as evoking ‘‘surprise disconfirmation’’ (Oliver, 1997; Oliver et al., 1997), andprovides basis f or understanding the cognitive foundation of delight.2.2. Affective basis of delightHowever, delight is much more than just another form of cognitive appraisal. Research on emotions in social psychology describes delight as a secondary-level emotion, which is characterized by a combination of lower level emotions. Plutchik (1980) proposed a ‘‘psychoevolutionary theory of emotion’’ which identifies eight basic emotions: joy, acceptance, fear, surprise, sadness, disgust, anger, an danticipation. He arranged these basic emotions in a circularpattern, called a circumplex, so that particular mixes of these basic emotions are possible. Therefore, these eight basic emotions can form primary, secondary, and tertiary dyads. Asecondary dyad may be described as a combination of two fundamental emotions result in higher order, more complex affects. Delight may be adequately described as a secondary dyad, consisting of a combination of joy and surprise(Plutchik, 1980). Other emotion frameworks similarly describe delight as a combination of arousal and pleasantness(Russell, 1980) or highly activated positive affect (Watsonand Tellegen, 1985). Finally, Richins (1997) developed theConsumption Emotion Set (CES), which identifies thoseemotions that are particularly relevant to the study ofconsumption in the marketing discipline. In this classification,delight is considered to be a descriptor of the ‘‘joy’’cluster. Other descriptors in this cluster include happy, glad,and cheerful.Consumer research has mirrored this conceptualizationof delight. Westbrook and Oliver (1991) studied the emotional profiles of automobile purchasers, and found difference samong respondents who reported satisfaction: one group experiencing happiness and contentment, and an other rexperiencing pleasant surprise, or delight. Oliver and Westbrook(1993) reported similar findings in that the group exhibiting the highest levels of joy and surprise were labeleddelighted. Oliver (1993) found significant relationships between positive affect (interest and joy) and satisfaction/dissatisfaction responses. Finally, Mano and Oliver (1993) showed different dimensions of positive–negative affect,including moderate arousal positive affect (pleasure), higharousalpositive affect (delight), and high nonspecific arousal(surprise).This research has increasingly recognized that suchemotions coexist with satisfaction judgments (cf., Manoand Oliver, 1993). Oliver (1997) notes that satisfaction‘‘modes’’ exist whereby different satisfactions are character rizedby the various affects attached to the satisfactionevaluation. For example, ‘‘satisfaction-as-delight’’ is character rize d by both expectation and disconfirmation processingthat result in a very intense primary affective response ofpleasant surprise or deligh t. Thus, delight appears to resultfrom a ‘‘blend’’ of pleasure and arousal, or more specifically,as a combination of joy and surprise (Oliver et al., 1997).2.3. Antecedents and consequences of delightIn addition to providing a better understanding of theconstruct of delight, recent research suggests a number ofantecedent constructs. The results of two structural modelsin two service settings (symphony patrons and wildlifeattendees) showed that delight was a function of surprisinglyhigh positive disconfirmation, arousal, and positive affect(Oliver et al., 1997). Structural differences were foundacross the two samples: delight directly affected repurchaseintentions only in the symphony sample, and indirectlyaffected intentions in the park sample.Outcomes of delight have generally focused on repurchase intentions. For example, researchers examining hedonic consumption have hypothesized that extremely positive,consumption-related emotions are likely to lead to very strong forms of commitment and repurchase intentions (Holbrookand Hirschman, 1982). Other research investigatingthe competitive implications of delight finds that generatingcustomer delight can pay off, but only if satisfaction stronglyaffects repurchase intention, the firm values future profits,satisfaction of competitors’ customers is important, and thefirm is able to attract dissatisfied customers of competitors(Rust and Oliver, 2000). Furthermore, generating delight among customers results in higher future expectations, thereby making it more difficult for the firm to generate delight repeatedly.Finally, a number of important consumer- and firm-level variables are likely to have moderating effects. For example,researchers have specifically suggested that both customerinvolvement and service variability are likely moderatinginfluences on the relationship between psychological antecedentconstructs and customer delight (Oliver et al., 1997).Furthermore, other research suggests the presence of moderatinginfluences on the delight–outcome relationship, suchas consumer self-regulation (Babin and Darden, 1995;Bagozzi et al., 1992; Kuhl, 1986), as well as more macrovariables,such as industry competitiveness (e.g., Andersonet al., 1994; Fornell, 1992).2.4. Unfavorable/dissatisfying experiencesAlthough the concept of ‘‘terrible’’ customer experienceshas not been defined or studied in retail settings, pastresearch has focused on identifying dissatisfying (and satisfying)incidents in service encounters. Bitner et al. (1990)examined favorable and unfavorable serviceencounters,based on the customer’s perspective, discovering that bothsatisfactory and unsatisfactory incidents could be attributedto one or more of three major types of employee behaviors:how the employee responded to a service delivery failure,how the employee responded to customer needs andrequests, and unprompted or unsolicited employee actions.Bitner et al. (1994) later investigated the sources of satisfactoryand dissatisfactory service encounters from theservice employee’s viewp oint. The results of this studyrevealed four groups of satisfactory and dissatisfactoryincidents: how employees responded to failures, to problemcustomers, and to requests, and unprompted action byemployees.Schneider and Bowen (1999) made an interesting argumentthat both customer delight and customer outrage stemfrom perceived justice or injustice. In a retail setting, if thecustomer’s needs for security, justice, and/or self-esteem areviolated in some way, a terrible shopping experience inwhich the customer may become filled with outrage mayresult. For example, a customer’s need for justice might beviolated if the customer was overcharged for an item or if a salesperson made promises or commitments to a customerthat were later broken. A customer’s need for self-esteemmight be violated if salespeople were uncaring and rude ordid not seem interested in assisting the customer. Thesesituations may indeed lead the customer to endure a terribleshopping experience.Keaveney (1995) identified critical incidents in service encounters that led to customer-switching behaviors. Among customers’ reasons for switching were inconvenience, pricing,core service failures, service encounter failures, employeeresponses to service failures, ethical problems, attractionby competitors, and involuntary switching. Ganesh et al.(2000) also investigated customer-switching behavior in aservices (banking) context, distinguishing customers whoswitched banks due to dissatisfaction from other groups ofcustomers. Finally, Kelley et al. (1993) identified types ofretail failures. Types of retail failures were categorized intothree groups: (1) employee responses to service deliverysystem or product failures; (2) employee responses to customerneeds and requests; and (3) unprompted and unsolicited employee actions.Given this background and the fact that neither ‘‘delightful’’nor ‘‘terrible’’ customer experiences in a retail shopping context has been examined, this exploratory researchdelves deeper into these issues by examining the factors thatproduce delightful as well as terrible shopping experiencesfor retail customers. The research method is discussed next,followed by a presentation of the results.3. MethodThe CIT was selected as the method to identify the underlying factors that led to delightful and terrible shopping experiences (Flanagan, 1954). Given that the phenomenon of customerdelight remains relatively unexplored in academic research, the CIT method was chosen as an exploratory research design, which emphasizes discovery over confirmation (Deshpande, 1983). The CIT has been used successfully in a number of retailing and services studies in which the goal was to provide research relevant to both managers and consumer researchers (Bitner et al., 1994; Keaveney, 1995; Ke lley et al., 1993). This particular method considers the ‘‘stories that people have told and asksquestions of the stories in order to classify each one within the scheme’’ (Bitner et al., 1990, p. 73).3.1. Data collectionThe CIT is a systematic procedure used for identifying events or behaviors that lead to certain outcomes, like success or failures on specific tasks (Bitner et al., 1990),satisfactions or dissatisfactions with a service provider (Bitner et al., 1994), or as reported here, delightful andterrible shopping experiences. Data were collected using the CIT with open-ended, structured interviews with a set of informants who were familiar with the phenomenon of interest (e.g., shopping and service patronage). The results of these interviews were then content analyzed with the purpose of identifying categories of critical incidents that lead to outcomes of interest (see Bitner et al., 1990, 1994; Ronan and Latham, 1974).Marketing research students trained in depth interviewing techniques conducted the interviews with nonstudent respondents. This project was a required component of a marketing research class. The use of students in data collection has been employed elsewhere (Gwinner et al., 1998), and particularly as interviewers when collecting data for critical incident analysis (Bitner et al., 1990, 1994). This approach provided the ability to investigate far greater numbers of transcribed interviews that would not be possible without such assistance, thereby providing a richer and more completeunderstanding of the constructs under investigation.The interviewers were given a detailed discussion guide that provided a series of questions to explore with the shopper–respondent. First, the respondent was primed by discussing with the interviewer how s/he feels about shopping in general across different retail formats. Then the hopper was asked to describe an experience s/he couldremember that was absolutely, positively delightful, where delight was explicitly described to the shopper as feelings of both joy or happiness, and surprise (cf. Oliver, 1997, 1999; Plutchik, 1980; Westbrook and Oliver, 1991).The interviewers probed by asking when, where, and how long the experience was, and what exactly was so delightful about this experience. Expectations were discussed, and the interviewers explored the feelings and thoughts the shopper had during the delightful experience and after it was over. The same process was employed for terrible shopping experiences, only, theinterviewers probed the shoppers to recall a shopping experience that was absolutely, positively terrible,one of the most unpleasant experiences the respondent shopper has ever had.Each interview lasted on average 30–45 min, and wastape recorded and transcribed into electronic for mat. Theinter viewers recorded the respondent’s name and telephone number for research verification purposes. No questionableinterviews were noted after following up by telephone witha random subset of respondents. A total of 123 interviews were conducted over the course of 1 month, and 10 were judged unusable, leaving a final sample of 113 informants. Approximately 68% were female and 32% were maleinformants. Respondents were free to recount their delightfuland terrible shopping experiences within any retail setting except grocery and drug stores. This resulted inthick descriptions of delightful and terrible shopping experiences,in a variety of retail settings: general mall experiences ,specialized clothing stores (e.g., Ann Taylor and bridal shops), specialized merchandisers (e.g., cigar store,music store and dive shop), discount/mass merchandisers(e.g., Wal-Mart and Target), upscale retailers (e.g., Dillard’sand Sax Fifth Avenue), electronics (e.g., Best Buy),furniture stores, automobile dealers, hardware stores, flea markets, and other miscellaneous retail formats (e.g., fabricstores and jewelry stores).4. Results and discussion The depth interviews provided a rich source of data in which to investigate the groups of factors characteristic ofboth delightful and terrible shopping experiences. Tables 1 and 2 show each of the major groups and categories within each group, along with the number of incidents counted for each category. Tables 3 and 4 present sample excerpts fromrespondents’ critical incidents fo r each of the categories for delightful shopping experiences and terrible shopping experiences.4.1. Delightful experiences—major groups and categoriewithin groups The sorting of the incidents led to two major groups of factors that appear to be associated with delightful shopping experiences: interpersonal and non-interpersonal. The interpersonal factor refers to situations when the source of the delightful experience is attributable to the actions of a salesperson or service provider. The non-interpersonal factor relates to situations in which the basis of the delightful experience springs from product procurement or value attainment. The critical incident analysis alsoproduced a group of outcomes associated with delightful experiences.4.1.1. Interpersonal factorsWithin the interpersonal group, five categories emerged from the data. Interpersonal effort refers to incidents in which the salesperson is extremely helpful in some way. For example, a salesperson may go out of his/her way to explain how a product functions or to provide additional product or service information. The second type of incident in the interpersonal group isinterpersonal engagement, which relates to situations in which the salesperson is extremel friendly and nice to the customer. These first two categories together are analogous to incidents grouped into a category called ‘‘attention paid to the customer,’’ which emerged in the Bitner et al. (1990) study. In that study, favorable encounters resulted when employees provided extra information, anticipated the customer’s needs, showed interest ina customer or were especially attentive to a customer.According to Bitner et al. (1990), behaviors, such as these, on the part of the salesperson, can make a customer feel unique and special. Problem resolution refers to instances in which the salesperson solves the customer’s problem, possibly even bending the rules’’ to accommodate the customer. For example, a customer’s warranty has expired, but the salesperson arranges for the product to be repaired free of charge The problem resolution factor found here is similar to the Bitner et al. (1990) ‘‘response to customer preferences,which may include an employee accommodating a request that goes beyond the scope of or is in violation of the company’s policies or rules. Kelley et al. (1993) found that correcting a problem or failure is an effective ‘‘recovery’’ tactic. In their study, 96% of respondents reported that they still shop at a retailer that corrected a problem or failure.According to Bitner et al. (1990), highly favorable encountersresult when the employee acknowledges the customer’sproblem and takes responsibility to solve it The term interpersonal distance is employed to describesituations in which a customer is delighted by a salesperson who is not too aggressive or ‘‘pushy.’’ Other delightful incidents may involve a salesperson spending a considerable amount of time assisting the customer or searching for a product. This category is referred to as time commitment. A salesperson calls t he retailers’ other locations to find a certain size, for instance. This factor is related to the ‘‘attention paid to the customer’’ group reported by Bitner et al. (1994).4.1.2. Non-interpersonal factorsCustomers were also delighted by occurrences other than salesperson behaviors. Oftentimes, a customer may unexpectedly locate a long-needed product or finds exactly what s/he is seeking. Thus, unanticipated acquisition is often associated with creating a delightful shopping experience.Unanticipated value, finding an unexpected bargain, or purchasing a product at a lower price than expected may also contribute to producing delight in a shopping situation.在零售方面的客户满意的和可怕的购物体验的调查Mark J. Arnold, Kristy E. Reynold, Nicole Ponder, Jason E. Lueg 摘要:欢乐的概念是极大的兴趣,从业者明白,为了保持客户的忠诚度,企业必须超越仅仅满足客户而是可以真正取悦他们,已经浮出水面的专门负责研究客户满意度的几项营销文献中,并没有运用作者的知识探讨在零售环境中的客户喜悦感。

五分钟搞定5000字外文翻译

五分钟搞定5000字外文翻译

五分钟搞定5000字-外文文献翻译
工具大全/node/2151
在科研过程中阅读翻译外文文献是一个非常重要的环节,许多领域高水平的文献都是外文文献,借鉴一些外文文献翻译的经验是非常必要的。

由于特殊原因我翻译外文文献的机会比较多,慢慢地就发现了外文文献翻译过程中的三大利器:G oogle“翻译”频道、金山词霸(完整版本)和CNKI“翻译助手"。

具体操作过程如下:
1.先打开金山词霸自动取词功能,然后阅读文献;
2.遇到无法理解的长句时,可以交给Google处理,处理后的结果猛一看,不堪入目,可是经过大脑的再处理后句子的意思基本就明了了;
3.如果通过Google仍然无法理解,感觉就是不同,那肯定是对其中某个“常用单词”理解有误,因为某些单词看似很简单,但是在文献中有特殊的意思,这时就可以通过CNKI的“翻译助手”来查询相关单词的意思,由于CNKI的单词意思都是来源与大量的文献,所以它的吻合率很高。

另外,在翻译过程中最好以“段落”或者“长句”作为翻译的基本单位,这样才不会造成“只见树木,不见森林”的误导。

注:
1、Google翻译:/language_tools
google,众所周知,谷歌里面的英文文献和资料还算是比较详实的。

我利用它是这样的。

一方面可以用它查询英文论文,当然这方面的帖子很多,大家可以搜索,在此不赘述。

回到我自己说的翻译上来。

下面给大家举个例子来说明如何用吧
比如说“电磁感应透明效应”这个词汇你不知道他怎么翻译,。

毕业设计 计算机专业外文翻译 5000字

毕业设计 计算机专业外文翻译 5000字

题目Programming Overlay Networkswith Overlay SocketsProgramming Overlay Networks with Overlay Sockets The emergence of application-layer overlay networks has inspired the development of new network services and applications. Research on overlay net-workshas focused on the design of protocols to maintain and forward data in an overlay network, however, less attention has been given to the software development process of building application programs in such an environment. Clearly,the complexity of overlay network protocols calls for suitable application programming interfaces (APIs) and abstractions that do not require detailed knowledge of the overlay protocol, and, thereby, simplify the task of the application programmer. In this paper, we present the concept of an overlay socket as a new programming abstraction that serves as the end point of communication in an overlay network. The overlay socket provides a socket-based API that is independent of the chosen overlay topology, and can be configured to work for different overlay topologies. The overlay socket can support application data transfer over TCP, UDP, or other transport protocols. This paper describes the design of the overlay socket and discusses API and configuration options.1 IntroductionApplication-layer overlay networks [5, 9, 13, 17] provide flexible platforms for develop-ing new network services [1, 10, 11, 14, 18–20] without requiring changes to the network-layer infrastructure. Members of an overlay network, which can be hosts, routers, servers, or applications, organize themselves to form a logical network topology, and commu-nicate only with their respective neighbors in the overlay topology. A member ofan overlay network sends and receives application data, and also forwards data intended for other members. This paper addresses application development in overlay networks. We use the term overlay network programming to refer to the software development process of building application programs that communicate with one another in an application-layer overlay_This work is supported in part by the National Science Foundation through grant work. The diversity and complexity of building and maintaining overlay networks make it impractical to assume that application developers can be concerned with the complexity of managing the participation of an application in a specific overlay networktopology.We present a software module, called overlay socket, that intends to simplify the task of overlay network programming. The design of the overlay socket pursues the following set of objectives: First, the application programming interface (API) of the overlay socket does not require that an application programmer has knowledge of the overlay network topology. Second, the overlay socket is designed to accommodate dif-ferent overlay network topologies. Switching to different overlay network topologies is done by modifying parameters in a configuration file. Third, the overlay socket, which operates at the applicationlayer,can accommodate different types of transport layer protocols. This is accomplished by using network adapters that interface to the un-derlying transport layer network and perform encapsulation and de-encapsulation of messages exchanged by the overlay socket. Currently available network adapters are TCP, UDP, and UDP multicast. Fourth, the overlay socket provides mechanisms for bootstrapping new overlay networks. In this paper, we provide an overview of the overlay socket design and discuss over-lay network programming with the overlay socket. The overlay socket has been imple-mented in Java as part of the HyperCast 2.0 software distribution [12]. The software has been used for various overlay applications, and has been tested in both local-area as well as wide-area settings. The HyperCast 2.0 software implements the overlay topolo-gies described in [15] and [16]. This paper highlights important issues of the overlay socket, additional information can be found in the design documentation available from[12]. Several studies before us have addressed overlay network programming issues. Evenearly overlay network proposals, such as Yoid [9], Scribe [4], and Scattercast [6], have presented APIs that aspire to achieve independence of the API from the overlay network topology used. Particularly, Yoid and Scattercast use a socket-like API, how-ever, these APIs do not address issues that arise when the same API is used by different overlay network topologies. Several works on application-layer multicast overlays inte-grate the application program with the software responsible for maintaining the overlay network, without explicitly providing general-purpose APIs.These include Narada [5], Overcast [13], ALMI [17], and NICE [2]. A recent study [8] has proposed a common API for the class of so-called structured overlays, which includes Chord [19], CAN [18], and Bayeux [20], and other overlays that were originally motivated by distributed hash tables. Our work has a different emphasis than [8], since we assume a scenario where an application programmer must work with several, possibly fundamentally dif-ferent, overlay network topologies and different transmission modes (UDP, TCP), and, therefore, needs mechanisms that make it easy to change the configuration of the un-derlying overlay network..Internet Overlay socket Application Overlay socket Application Application Overlay socket Application Application Overlay socket Application Overlay Network. Fig. 1. The overlay network is a collection of overlay sockets. Root (sender) Root (receiver) (a) Multicast (b) Unicast.Fig. 2. Data forwarding in overlay networks.The rest of the paper is organized as following. In Section 2 we introduce con-cepts, abstractions, and terminology needed for the discussion of the overlay socket. In Section 3 we present the design of the overlay socket, and discuss its components. In Section 4 we show how to write programs using the overlay socket. We present brief conclusions in Section 5.2 Basic ConceptsAn overlay socket is an endpoint for communication in an overlay network, and an overlay network is seen as a collection of overlay sockets that self-organize using an overlay protocol (see Figure 1). An overlay socket offers to an application programmer a Berkeley socket-style API [3] for sending and receiving data over an overlay network.Each overlay socket executes an overlay protocol that is responsible for maintaining the membership of the socket in the overlay network topology. Each overlay socket has a logical address and a physical address in the overlay network. The logical address is dependent on the type of overlay protocol used. In the overlay protocols currently implemented in HyperCast 2.0, the logical addresses are 32- bit integers or_x_y_coordinates, where x and y are positive 32-bit positive integers. The physical address is a transport layer address where overlay sockets receive messages from the overlay network. On the Internet, the physical address is an IP address and a TCP or UDP port number. Application programs that use overlay sockets only work with logical addresses, and do not see physical addresses of overlay nodes. When an overlay socket is created, the socket is configured with a set of configu-ration parameters, called attributes. The application program can obtain the attributes from a configuration file or it downloads the attributes from a server. The configuration file specifies the type of overlay protocol and the type of transport protocol to be used,.but also more detailed information such as the size of internal buffers, and the value of protocol-specific timers. The most important attribute is the overlay identifier (overlay ID) which is used as a global identifier for an overlay network and which can be used as a key to access the other attributes of the overlay network. Each new overlay ID corresponds to the creation of a new overlay network. Overlay sockets exchange two types of messages, protocol messages and application messages. Protocol messages are the messages of the overlay protocol that main-tain the overlay topology. Application messages contain applicationdata that is encap-sulatedn an overlay message header. An application message uses logical addresses in the header to identify source and, for unicast, the destination of the message. If an overlay socket receives an application message from one of its neighbors in the over-laynetwork, it determines if the message must be forwarded to other overlay sockets, and if the message needs to be passed to the local application. The transmission modes currently supported by the overlay sockets are unicast, and multicast. In multicast, all members in the overlay network are receivers.In both unicast and multicast,the com-mon abstraction for data forwarding is that of passing data in spanning trees that are embedded in the overlay topology. For example, a multicast message is transmitted downstream a spanning tree that has the sender of the multicast message as the root (see Figure 2(a)). When an overlay socket receives a multicast message, it forwards the message to all of its downstream neighbors (children) in the tree, and passes the mes-sage to the local application program. A unicast message is transmitted upstream a tree with the receiver of the message as the root (see Figure 2(b)). An overlay socket that receives a unicast message forwards the message to the upstream neighbor (parent) in the tree that has the destination as the root. An overlay socket makes forwarding decisions locally using only the logical ad-dresses of its neighbors and the logical address of the root of the tree. Hence, there is a requirement that each overlay socket can locally compute its parent and its children in a tree with respect to a root node. This requirement is satisfied by many overlay network topologies, including [15, 16, 18–20].3 The Components of an Overlay SocketAn overlay socket consists of a collection of components that are configured when the overlay socketis created, using the supplied set of attributes. These components include the overlay protocol, which helps to build and maintain the overlay network topology, a component that processes application data, and interfaces to a transport-layer network. The main components of an overlay socket, as illustrated in Figure 3, are as follows:The overlay node implements an overlay protocol that establishes and maintains the overlay network topology. The overlay node sends and receives overlay protocol messages, and maintains a set of timers. The overlay node is the only component of an overlay socket that is aware of the overlay topology. In the HyperCast 2.0. Overlay socket Forwarding EngineApplication Programming InterfaceStatistics InterfaceProtocol MessagesApplicationReceiveBufferApplicationTransmitBuffer Overlay NodeO verlay NodeInterfac eNode AdapterAdapter InterfaceSocket AdapterA dapter InterfaceApplication MessagesApplication ProgramTransport-layer NetworkApplication MessagesFig. 3. Components of an overlay socket.software, there are overlay nodes that build a logical hypercube [15] and a logical Delaunay triangu-lartion [16].The forwarding engine performs the functions of an application-layer router, that sends, receives, and forwards formatted application-layer messages in the overlay network. The forwarding engine communicates with the overlay node to query next hop routing information for application messages. The forwarding decision is made using logical addresses of the overlay nodes. Each overlay socket has two network adapters that each provides an interface to transport-layer protocols, such as TCP or UDP. The nodeadapter serves as the in-terface for sending and receiving overlay protocol messages, and the socket adapter serves as the interface for application messages. Each adapter has a transport level address, which, in the case of the Internet, consists of an IP address and a UDP or TCP port number. Currently, there are three different types of adapters, for TCP, UDP, and UDP multicast. Using two adapters completely separates the handling of messages for maintaining the overlay protocol and the messages that transport application data.The application receive buffer and application transmit buffer can temporarily store messages that, respectively, have been received by the socket but not been deliv-ered to theapplication, or that have been released by the application program, but not been transmitted by the socket. The application transmit buffer can play a role when messages cannot be transmitted due to rate control or congestion control con-straints. The application transmit buffer is not implemented in the HyperCast 2.0 software.Each overlay socket has two external interfaces. The application programming in-terface (API) of the socket offers application programs the ability to join and leave existing overlays, to send data to other members of the overlay network, and receive data from the overlay network. The statistics interface of the overlay socket provides access to status information of components of the overlay socket, and is used for monitoring and management of an overlay socket. Note in Figure 3 that some components of the overlay socket also have interfaces, which are accessed by other components of the overlay socket. The overlay manager is a component external to the overlay socket (and not shown in Figure 3). It is responsible for configuring an overlay socket when the socket is created. The overlay manager reads a configuration file that stores the attributes of an overlay socket, and, if it is specified in the configuration file, may access attributes from a server, and then initiates the instantiation of a new overlay socket.4 Overlay Network ProgrammingAn application developer does not need to be familiar with the details of the components of an overlay socket as described in the previous section. The developer is exposed only to the API of the overlay socket and to a file with configuration parameters.The configuration file is a text file which stores all attributes needed to configure an overlay socket. The configuration file is modified whenever a change is needed to the transport protocol, the overlay protocol, or some other parameters of the overlay socket. In the following, we summarize only the main features of the API, and we refer to [12] for detailed information on the overlay socket API.4.1 Overlay Socket APISince the overlay topology and the forwarding of application-layer data is transparent to the application program, the API for overlay network programming can be made simple. Applications need to be able to create a new overlay network, join and leave an existing overlay network, send data to and receive data from other members in the overlay.The API of the overlay socket is message-based, and intentionally stays close to the familiar Berkeley socket API [3]. Since space considerations do not permit a description of the full API, we sketch the API with the help of a simplified example. Figure 4 shows the fragment of a Java program that uses an overlay socket. An application program configures and creates an overlay socket with the help of an overlay manager (o m). The overlay manager reads configuration parameters for the overlay socket from a configu-ration file (hypercast.pro p), which can look similarly as shown in Figure 5. The applica-tion program reads the overlay ID with command om.getDefaultProperty(“OverlayID”) from the file, and creates an configuration object (confi g) for an overlay socket with the.// Generate the configuration object OverlayManager om = newOverlayManager("hypercast.prop");String MyOverlay = om.getDefaultProperty("OverlayID"); OverlaySocketConfig config = new om.getOverlaySocketConfig(MyOverlay); // create an overlay socketOL Socket socket = config.createOverlaySocket(callback);// Join an overlaysocket.joinGroup();// Create a messageOL Message msg = socket.createMessage(byte[] data, int length);// Send the message to all members in overlay networksocket.sendToAll(msg);// Receive a message from the socketOL Message msg = socket.receive();Fig. 4. Program with overlay sockets.# OVERLAY Server:OverlayServer =# OVERLAY ID:OverlayID = 1234KeyAttributes= Socket,Node,SocketAdapter# SOCKET:Socket = HCast2-0HCAST2-0.TTL = 255HCAST2-0.ReceiveBufferSize = 200# SOCKET ADAPTER:SocketAdapter = TCPSocketAdapter.TCP.MaximumPacketLength = 16384# NODE:Node = DT2-0DT2-0.SleepTime = 400# NODE ADAPTER:NodeAdapter = NodeAdptUDPServer NodeAdapter.UDP.MaximumPacketLength = 8192 NodeAdapter.UDPServer.UdpServer0 =128.143.71.50:8081Fig. 5. Configuration file (simplified) given overlay ID. The configuration objectalso loads all configuration information from the configuration file, and then creates the overlay socket(config.createOverlaySocke t).Once the overlay socket is created, the socket joins the overlay network (socket.join-Grou p). When a socket wants to multicast a message, it instantiates a new message (socket.createMessage) and trans-mits the message using the sendToAll method. Other transmission options are send-To-Parent, send-To-Children, sendToNeighbors, and sendToNode, which, respectively, send a message to the upstream neighbor with respect to a given root (see Figure 2), to the downstream neighbors, to all neighbors, or to a particular node with a given logical address.4.2 Overlay Network Properties ManagementAs seen, the properties of an overlay socket are configured by setting attributes in a configuration file. The overlay manager in an application process uses the attributes to create a new overlay socket. By modifying the attributes in the configuration file, an application programmer can configure the overlay protocol or transport protocol that is used by the overlay socket. Changes to the file must be done before the socket is created. Figure 5 shows a (simplified) example of a configuration file. Each line of the configuration file assigns a value to an attribute. The complete list of attributes and the range of values is documented in [12]. Without explaining all entries in Figure 5, the file sets, among others, the ov erlay ID to …1234 ‟, selects version 2.0 of the DT protocol as overlay protocol (…Node=DT2-0 ‟), and it sets the transport protocol of the socket adaptor to TCP(…SocketAdapter=TCP ‟).Each overlay network is associated with a set of attributes that characterize the properties of the over-lay sockets that participate in the overlay network. As mentioned earlier, the most important attribute is the overlay ID, which is used to identify an y network, andwhich can be used as a key toaccess all other attributes of an overlay network. The overlay ID should be a globally unique identifier.A new overlay network is created by generating a new overlay ID and associating a set of attributes that specify the properties of the overlay sockets in the overlay network. To join an overlay network, an overlay socket must know the overlay ID and the set of attributes for this overlay ID. This information can be obtained from a configuration file, as shown in Figure 5.All attributes have a name and a value, both of which are strings. For example, the overlay protocol of an overlay socket can be determined by an attribute with name NODE. If the attribute is set to NOD-E=DT2- 0, then the overlay node in the overlay socket runs the DT (version 2) overlay protocol. The overlay socket distinguishes between two types of attributes: key attributes and configurable attributes. Key attributes are specific to an overlay network with a given overlay ID. Key attributes are selectedwhen the overlay ID is created for an overlay network, and cannot be modified after-wards.Overlay sockets that participate in an overlay network must have identical key attributes, but can have different configurable attributes. The attributes OverlayID and KeyAttributes are key attributes by default in all overlay networks. Configurable at-tributes specify parameters of an overlay socket, which are not considered essential for establishing communication between overlay sockets in the same overlay network, and which are considered …tunable‟.5 ConclusionsWe discussed the design of an overlay socket which attempts to simplify the task of overlay network programming. The overlay socket serves as an end point of commu-nication in the overlay network. The overlay socket can be used for various overlay topologies and support different transport protoc-ols. The overlay socket supports a simple API for joining and leaving an overlaynetwork, and for sending and receiving data to and from other sockets in the overlay network. The main advantage of the overlay socket is that it is relatively easy to change the configuration of the overlay network. An implementation of the overlay socket is distributed with the HyperCast2.0 soft-ware. The software has been extensively tested. A variety of different applications, such as distributed whiteboard and a video streaming application, have been developed with the overlay sockets. Acknowledgement. In addition to the authors of this article the contributors include Bhupinder Sethi, Tyler Beam, Burton Filstrup, Mike Nahas, Dongwen Wang, Konrad Lorincz, Jean Ablutz, Haiyong Wang, Weisheng Si, Huafeng Lu, and Guangyu Dong.应用层覆盖网络的出现促进了新网络服务和应用的发展。

毕 业 设 计(英文翻译)

毕 业 设 计(英文翻译)

附录G:英文翻译参考(要求学生完成与论文有关的外文资料中文字数5000字左右的英译汉,旨在培养学生利用外文资料开展研究工作的能力,为所选课题提供前沿参考资料。

)毕业设计(英文翻译)题目系别:专业:班级:学生姓名:学号:指导教师:一位从事质量管理的人约瑟夫·朱兰出生于圣诞夜,1904 在罗马尼亚的喀尔巴阡山脉山中。

他青年时期的村庄中贫穷、迷信和反犹太主义甚是猖獗。

1912年朱兰家搬到了明尼阿波尼斯州,虽然充满了危险,但是它却让一个男孩充满信心和希望。

从如此多了一个在质量观念的世界最好改革者之一。

在他90年的生活中,朱兰一直是一个精力充沛的思想者倡导者,推动着传统的质量思想向前走。

因为九岁就被雇用,朱兰表示在他的生活工作上永不停止。

记者:技术方面如何讲质量?朱兰:技术有不同方面:一、当然是精密。

物的对精密的需求像电子学、化学…我们看来它们似乎需要放大来说,和重要的原子尘的有关于质量。

要做到高精密具有相当大的挑战,而且我们已经遇见非常大的挑战。

另外的一个方面是可信度-没有失败。

当我们举例来说建立一个系统,同类空中交通管制的时候,我们不想要它失败。

我们必须把可信度建入系统。

因为我们投入很大的资金并依赖这些系统,系统非常复杂,这是逐渐增加的。

除此之外,有对公司的失败费用。

如果事物在领域中意外失败,可以说,它影响民众。

但是如果他们失败在内部,然后它影响公司的费用,而且已经试着发现这些费用在哪里和该如何免除他们。

因此那些是相当大的因素:精密、可信度和费用。

还有其它的,当然,但是我认为这些是主要的一些。

记者:据说是质量有在美国变成一种产业的可能?朱兰:资讯科技当然有。

已经有大的变化。

在世纪中初期当质量的一个想法到一个检验部门的时候,这有了分开的工作,东西被做坏之后。

检验是相当易错的程序,实际上。

而且无论如何,资讯科技在那天中相当花时间,直到某事已经被认为是否资讯科技是正确的。

应该强调计划,如此它不被错误首先订定。

五千字外文翻译

五千字外文翻译

SCRAPER WINCH MOTORS ON SOUTH AFRICAN GOLD MINES – ANINVESTIGATION INTO THEIR FAILUREJF Pritchard CF LandyDept. of Electrical EngineeringABSTRACTThis paper investigates some of the probable reasons forfailure of squirrel cage induction machnes dnving scraperwinches in South African Gold Mines. The paper shows theresults of load current and voltage unbalance measurements that were recorded on winches in operation. There arefurther measurements showing the presence of time harmonics in the supply to some winches. More importantly,the paper shows the measured torque-speed curve of atypicai scraper winch machine. This curve seems to inhace that there are significant space harmonics present in the air gap of the winches, which may be causing rotor heating and pre-mature bearing failure.INTRODUCTIONIn South African gold mines, a winch known as a “scraper winch” is used to scrape ore-bearing rock from the rock -face after blasting. The winch consists of a mechanical winch powered by a squirrel cage induction motor. The mostcommon rating for the scraper winch motor is 37kW, 525V,5 1A.It is well known in the SA mining industry that these winches do not last for more than about 4 to 6 months in operation underground before they bum out and have to be sent to the surface for re-winding. A number of theories have been advanced by engineers working on the mines as to why these machines fail so often, however, none of these theories have so far been adequately documented or proven.Scraper winches normally operate in the stopes (the sections where mining operations are on-going) and as such, it is difficult to install and remove them easily since the railway lines underground do not extend all the way into the stopes. Once a winch bums out, it may often take up to 2 to 3 full shifts before a new winch can be installed in its place and as a result, a significant amount of production is lost. If one considers that a large gold mine with more than one active shaft, may have up to 1000 scraper winches in operation at any one time (and these winches are being replaced on average, twice a year), and one factors in the cost of rewinds as well as lost production, it becomes evident that scraper winches are costing the gold mining industry a lot of money every year. This paper highlights some research that has been done at the University of the Witwatersrand to investigate the reasons for failure of scraper winch motors in South African gold mines. The paper describes part of the preliminary investigation that involved researchmg literature on squirrel cage induction machine failures as well as the results of visits to machine repair organisations involved with winch motor repairs for the mines. Thereafter, the results of measurements that were taken underground are discussed. Laboratory tests that were camed out on scraper winch motors are also highlighted and the results thereof are discussed.THE PRELIMINARY INVESTIGATIONThe reasons for squirrel cage induction machine failures are quite well documented in the literature [1,2,3,7]. It seems that in meQum voltage, small machmes, the predominant componentthat fails is the stator winding insulation. Stator failures can often be attributed to electrical supply problems such as voltage unbalance, single phasing, time harmonic voltages in the supply, undervoltage, overvoltage and voltage transients. There are also load factors such as mechanical overloading of the machine, and thermal cycling of the insulation that can lead to thermal as well as mechanical ageing of the insulation. Environmental factors111 are also often cited as stresses that act on the stator insulation. In particular, voltage tracking (even in med” voltage motors) across the slot insulation due to moisture and dirt finding their way inside the machne is a common rea son for failures in machines that operate in “dusty”environments. Clogging of the airways, corrosion of the laminations and deterioration of the insulation due to moisture [1,4] are also sometimes quoted as environmental reasons for failure. Mechanical abrasion of the insulation due to foreign particles entering the machine may also lead to machine failure.DriR-uroof machinesDuring the investigation, a number of failed scraper winch motors were observed at two machine repair organizations. Of these, the majority were enclosed in drip-proof enclosures, while some were housed in totally enclosed, fan cooled enclosures (TEFC enclosures). The drip proof machines were found to all have evidence of rust on the stator cores, with small stones and mine sludge being found in the overhangs of the machines. Large amounts of grease and oil were also found inside most machines, which came either from the bearings, or from the gear-box to whch the machines are attached, or both. In one case a stone of 3cm diameter was found in the overhang. One repairer claimed that he sometimes finds it necessary to press the rotor out of the stator using a machine (once the bearings were of€) due to the large number of foreign particles jammed into the air gap. Regarding the drip-proof machines, it became evident hat a major factor leading to failure was abrasion of the stator insulation due to the presence of foreign particles inside the machine.Because of these obvious short-comings associated with drip-proof motors, according to one source in the mining industry, most of the mines nowadays purchase only TEFC machines. For this reason, it was decided to neglect drip proof machines in the investigation and focus solely on TEFC machines.TEFC machinesOf the failed TEFC machines, it seemed that there was also evidence of rust and sometimes grease inside some of the “sealed‟ machines, however, it was of a lesser extent compared to the drip-proof machines. It seems that the grease found in these machines also worked its way into the sealed housing from the bearings and the adjacent gear-box. The appearance of rust in supposedly “sealed machines is also not dflicult to explain if one considers that when a machine is run, the air inside heats up and expands, hence pressure the seals and some of it may find its way out. When the machine is allowed to cool, the air inside contracts and a partial vacuum is established which may allow moisture-laden air to enter the machine, depending on how well it is sealed.Both machne repairers claimed that when machines come in for repair they sometimes findthat an earth fault that…was noticed when the machine came in initially, is alleviated when the machine is opened up and dried out. Also, it seems that the bearings are almost always in need of replacement and the machine repairers replace the bearings every time asa matter of course. Based on this evidence, it seems that bearing failures and voltage traclung due to moisture may at least be one component leading to TEFC scraper winch failures.pH measurements inside failed machinesSome engineers have claimed that scraper winches fail because of non-balanced pH aqueous solutions finding their way onto the stator winding and corroding it. While it is not clear that an acidic or alkali solution does in fact corrode the insulation or the impregnating varnish faster than normal water [4], it was decided to check if this may in fact be one additional factor to consider.A relatively recent paper in a mining journal [5] indicates that fissure water in South African gold mines has a pH value that varies from 2.67 in some areas in the Witwatersrand to 9.77 in the Free State. Furthermore,another paper was found [6] that showed that significant amounts of nitrous fumes are given off during the blasting process whch can combine with water vapour (of which there is an abundance underground) to produce nitrous acid. Since the scraper motors are very near to the blasting area and are always in the presence of water vapour, it seems that dilute acids and alkalis may find their way into scrapermachmes in some mines.As a further test, a sample of 10 failed, drip proof machines (since they are more exposed to the environment than TEFC machines) from 2 mines in the Witwatersrand were opened up and tested for pH content using colour fixed pH indxator sticks (with a pH accuracy of 1). The procedure was to dip the sticks into distilled water and then press them against the inside of the stator bore in 4 different places. Of all the machines that were tested, not one registered a pH content of other than 7 (balanced), indicating that there was no sigruficant acid or alkali concentration inside the machines. Although this was a rather crude experiment on a very small sample of machines, it does seem to indicate that pH content is not a real factor when looking for reasons for failure of scraper winch motors.UNDERGROUND MEASUREMENT RESULTSIn order to assess the quality of the supply to scraper winch motors underground, as well as to assess the loading on the machines, it was decided to log measurements of the three phase line current, voltage and power to a series of machines in operation underground. Coupled with this, it was decided to record spot current waveforms for analysis later.The data was sampled and logged on a portable computer using a 16 bit data acquisition card PAC). The measurement transducers consisted of two wide bandwidth, battery powered current probes and two small voltage transformers. These were connected to a unit housing a high order anti-aliasing filter, which in turn passed the signal to the DAC. The voltage and current on two lines was measured directly using the transducers and the voltage and current on the other 2 phases was inferred using the fact that the voltage and current in a 3 phase, 3 wire system sum to zero. The input power was measured using the standard 2 wattmeter method,using the voltage and current transducers, with the multiplication etc., being done in the software.The software was set up in such a way as to allow the DAC to sample at 15& and acquirebatches of 3000 points. This enabled a true RMS reading of all 3 line voltages and currents to be taken roughly every 314 of a second and recorded. The high loggmg frequency was necessary in order to capture machmes running up, as well as rapid load changes which can happen in less than a second. The current waveforms that were captured were also sampled at 15&, with 60000 points being stored. This was done to give a frequency resolution of 0.25Hi in the frequency domain.Due to the physical constraints involved with measuring underground, it was only possible to log data measured at one machine site for three shifts. Unfortunately, the only suitable site for measurement was in an area of the mine where the machines were not being pushed too hard (according to some miners) because of the relatively short haulage path for the winches (for more discussion of the actors affecting loading on the machine, see [lo]). While the results that were recorded may presumably not be taken to be true of scraper winches in general, they do give what appears to be a good indication of the duty cycle of scraper winches. Figures 1-3 below show the average current (i.e. the sum of all three phases divided by 3) that was recorded over 3 shifts of operation.It is clear from the current plots that the scraper winch being observed has a highly irregular duty cycle. It is also clear from the plots that the amount of loading is very irregular. The large current peaks correspond to starting current peaks. The reason some starting peaks are less than others is to do with the fact that the sample batches were not synchronised with the starting of the machine. Since the machme can run up to speed in almost a second (there is no load during starting), the lower starting peaks correspond to a sample batch that was taken by the time the machine had almost run up to speed.If one analyses the data in the plots carefully, it becomes evident that the worst case duty cycle is 60% of one hour, while the average duty cycle is 50%. Th e average “on time” per start (as calculated over all 3 shifts) is 5 minutes, while the average number of starts per half hour is 3. The maximum number of starts per half hour is 5. The average on time per half hour is 15 minutes.The plots show that apart from starting and one or two short periods of overload, this machine was not heavily loaded over the three nights of observation (the rated current is 51A). In order to definitively state the average load current for a 37kW scraper winch in operation, one would have to take more measurements on a larger variety of machines in operation than these.Regarding voltage unbalance, one may state the % unbalance as follows [7]:%100%⨯-=average averagev v v unbalancewhere V is the RMS line voltage of a particular line. The worst case voltage unbalance over all three shifts is shown for the affected phase in figure 4 below.The figure shows that apart from one short period ofsubstantial voltage unbalance, there was no real voltage unbalance in the supply to the observed machine. Most researchers say that asupply voltage unbalance of up to 3% is acceptable for most induction motors, however in this case, the unbalance is almost always less than 1%.If one plots the average 3 phase line voltage out and averages that over the periods that the machine is on, one finds that at the site in question, the scraper winch was supplied with an average voltage of 500V during its “on” periods. While the rated voltage is 525V, this machine was not affected at all by a corresponding overcurrent as the plots on the previous page show. The time domain current waveform that was captured underground during the machine‟s operation was processed afterwards by performing a fast Fourier transform on it. The FFT was done in Matlab@, with due attention being given to spectral leakage effects. The frequency domam data of relevance is plotted in the figure below. The current amplitudes are normalised to the 50Hz current and are given in decibels (2010glo(actual magnitude)).The plot in figure 5 shows that there are significant third and fifth harmonic currents present in the stator current (magnitudes are 1.6% and 4.4% of the fundamental respectively). These time harmonics, particularly the fifth harmonic (which is negative phase sequence) can cause considerable heating of the rotor circuit (Gomes [9]). The harmonic content and magnitude may vary from region to regon within a mine and even more so from mine to mine, however the harmonic currents shown in this plot (particularly the ffih harmonic) are unacceptably high and will definitely contribute towards shortening the life of themachine.LABORATORY TEST WSULTSFor the laboratory work, 2 scraper winch motors were tested. A TEFC machme which had been in service for some time on a mine and had been re-wound recently was initially tested. It had not been in service since the re-wind. The second machine was new and was supplied by the manufacturer. When the two machines were stripped and compared, it was found that their electrical designs were identical and their mechanical designs were almost identical, with only minor differences in the casing being noticed.It was decided that the amount of loadmg shown in figures (1-3) could not be taken to be a typical load on a scraper winch motor in operation and hence for the laboratory tests, the rated current was used. However, it was decided that the duty cycle information in the plots may be considered typical. Since it was anticipated that the bearings of the machine would be getting too hot, heat sensors (resistive temperature detectors - RTD‟s) were fitted into holes drilled in the end-shields of the machine from the mine (machine 1) and pushed up against the outer race of the bearings. In addition, an RTD was placed on each overhang, as close as possible to the core. These sensors were placed at the top of the overhang on the outside and were held in place by some silicon gel. A number of heat runs were done at rated output power and Werent duty cycles. These results are plotted in the table below.The machine was operated at a voltage of between 490 and 500V and the rated current for this voltage was calculated by working out the losses for the machine at a range of currents and then calculating the output power by subtracting the machine losses from the input power.The table shows that for the cases where the average winding temperature rise was measured (done by measuring the change in the DC stator windmg resistance), the average temperature was higher than the overhang temperatures.This is because the overhang temperature sensors are only able to measure the temperature at a point, whereas the average winding resistance method inherently averages the temperature distribution around the machine inside the conductors themselves.The shaft temperature measurements indicated above were taken using a temperature probe which was positioned as close to the drive end end-shield as possible, immediately after the machine stopped. To a first approximation, the shaft temperature rise was taken to indicate the temperature rise of the inner drive end bearing race.If one considers that the ambient temperature in the vicinity of a scraper winch in operation in a mine may be as high as 35°C typically, the actual temperatures measured would be those in the table plus 35°C. Thls would place the shaft temperature at 112°C for the worst case and 95°C for the best case condition in the table. The diagram below shows the actual assembly of the drive end bearing and shaft for the machine under test.If one considers that the shaft temperature is measured immediately adjacent to the oil seal as shown in the diagram, it is conceivable that the temperature of the bearing seal (on the bearing side closest to the rotor) is because of the space displacement.According to the bearing manufacturers, a sealed bearing may not operate at a temperature of higher than 110°C without the lubricant leaking out. In this case, after about 10 different heat runs were done, all at or below rated current, it was noticed that there was a sigNticant amount of lubricant lying under the machine. When the machine was stripped, it was found that there was a large pool of lubricant inside the bearing housing as well as inside the machine next to the stator overhang. Also, the rotor steel had become extremely dark indicating that the rotor was getting very hot during operation. This evidence was consistent with the observations made at the machine repairers where it was found that there were large quantities of grease lying inside the machine housing.The second machine (the new machine) was subsequently coupled to the load being used (a DC machine) and a continuous heat run was performed on it. The rated current of the machine (as given by the manufacturers) is 51A, but because the machine was being fed by 500V instead of 525V, the heat run was performed at a load current of 54A. In this case, the machme had heat sensitive strips pasted inside; on the shaft, end-rings and the bearing seals facing the rotor. After the machine had run continuously for 4 hours and 40 minutes, the drive end bearing seized completely and the machine stalled. When the machine was opened, all the temperature strips had gone off-scale.The results from these tests showed that although the stator winding wasn‟t getting excessively hot for class F insulation, the rotors were getting extremely hot and damaging the bearings. It was suspected at this stage that the machine rotors were getting hot because of large high frequency currents flowing in the rotor bars due to space harmonic effects in the air-gap of the machine.Landy [9] shows that harmomc currents of significant magnitude flowing in the rotors ofinduction machmes can be picked up by measuring the torque speed curve of the machine under reduced voltage conditions. The harmonic mmfs caused by the stepped nature of the mmf wave in the air gap, produce harmonic currents in the rotor circuit. These harmonic currents in turn produce a “family” of harmonic“ f s of their own which interact with the stator mmf waves to produce either asynchronous or synchronous torques which will be superimposed on the fundamental torque speed envelope. Figure 6 below shows the measured torque speed w e of the new machine (which is the same as that of the older machine) along with the curve that would be expected if there were no space harmonics present in the machine. For convenience, the curve has been normalised with respect to the maximum pull-out torque.It is obvious from figure 7 that there are very significant space harmonic effects in the air-gap of the machmes under test. The machines have relatively deep rectangular bars and if there are large, high frequency rotor harmonic currents (as the torque-speed curve suggests), they will flow close to the top of the bar and cause severe heating of the rotor bars and the rotor as a whole.CONCLUSIONSThis paper has shown that there are a number of factors that may be shortening the life of TEFC scraper winch motors. In particular, it appears that at some machine sites underground, there are time harmonic voltages present in the supply to the machines which can cause unacceptable heating of the machines and hence reduce their life. V oltage unbalance does not appear to be a problem, but there is evidence that there is a lower voltage than 525V at some Sites.Furthermore, as was evidenced by observations of failed machines, there appear to be numerous incidences of moisture getting into the machine windings whilst in operation underground. This can assist voltage tracking across the insulation and cause an earth or phase-phase fault inside the machine. The moisture can also damage the machine bearings and stator laminations with time.Coupled with this evidence, the paper shows strong experimental evidence which suggests that typical 37kW scraper winch motors may be experiencing bearing failures induced byexcessive rotor generated heat. As a feasible explanation for this, a measurement of the steady-state torque speed curve of two 37kW, TEFC scraper winch motors reveals that there appear to be large magnitude, high frequency currents circulating in the rotor bars. Thus, even though the loading experienced by a scraper winch may be lower than the rated current (as was shown for a particular winch underground), that winch may still experience a bearing failure because of the space harmonic rotor heating effects. A further analysis of the space harmonic effects expected in the winch motors in the laboratory is being undertaken at present, with a view to recommendmg design changes to the standard scraper winch motors.ACKNOWLEDGEMENTSThe authors would like to thank AngloVad Minerals and Hartebeestfontein Gold Mine for their financial assistance and for supplying a scraper winch for laboratory work. In addition, the authors would like to acknowledge the assistance of Powermote (PTY) LTD who supplied a scraper winch as well, and gave some details on its design. Finally, thanks must also go to the Eskom TESP program for further financial assistance and to the University of the Witwatersrand who supplied the laboratory facilities for the research.REFERENCES1. Bonnet A.H., Soukop G.C., Cause andAnalysis of Stator and Rotor Failures in Three-phase Squirrel-Cage Induction Motors, IEEE Transactions on Industry Applications, V ol. 28, No.4, JulyIAugust 19922.Bonnet A.H., Soukop G.C, Rotor Failures in Squirrel-Cage Induction Motors, LEEE Transactions on Industry Applications, V ol. IA-22, No. 6, NovemberDecember 2.1986, pp 1165-1 1733. Bonnet A.H., Analysis of Winding Failures in Three-Phase Squirrel Cage Induction Motors, IEEE Transactions on Industry Applications, V ol. IA- 14, No. 3, MayJJune 1978 pp. 223-2264. Campbell F. J., Temperature Dependance of Hydrolysis of Polyimide Wire Insulation, IEEE Transactions on Electrical Insulation V ol. EI-20 No.1, February 1985,5.Pulles W., Water Pollution: ItsManagement and Control in the South African Gold Mining Industry, Journal of the Mine Ventilation Society of South Africa, february 1992, pp 18-36,pp 11 1-1 166. Burton R.C. and Wrigley D.E., Blast Fume Filters in Mines - A Review of the Current State of the Art, Journal of the Mine Ventilation Society of South Africa, October 1991, pp 167-1717.Woll R.F., Effect of Unbalanced V oltage on the Operation of Polyphase Induction Motors, IEEE Transactions on Industry Applications, V ol. IA-11, No.1, January/February 1975, pp 38-428.Gomes A.A.D.F.P, Landy C.F., The Effects of Supply Time Harmonics on the Torque Speed Curves of Squirrel Cage Induction Machines, proc. IEEE Intemational Conference on Electrical Machines-Design and Application, London, July 1982, p104ndy C.F., A Technique For Assessing Space Harmonic Effects in Squirrel Cage Induction Motors, SAJEE Transactions, vol73, part 1, 1982, pp 3-1110. Pritchard J.F., An Investigation into the Reasons for Failure of Scraper Winch Motors on South African GoldMines, M.Sc. (eng.) Thesis, University of the Witwatersrand, 1996 Authorized licensed中文译文南非金矿的刮刀绞盘电机-他们的失败调查摘要本文研究的是在南非金矿使用的刮板绞车采用的鼠龙式异步电机故障的原因。

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山东理工大学英-中文翻译材料英文题目:Brief Introduction中文题目:.NET简介学院:计算机科学与技术专业:软件工程学生姓名:米东文指导教师:刘秋香二O一五年六月Brief Introduction to .NETThe .NET FrameworkThe .NET Framework is a multi-language environment for building, deploying, and running XML Web services and applications. It consists of three main parts:∙Common Language Runtime Despite its name, the runtime actually has a role in both a component's runtime and development time experiences. While the component is running, the runtime is responsible for managing memory allocation, starting up and stopping threads and processes, and enforcing security policy, as well as satisfying any dependencies that the component might have on other components. At development time, the runtime's role changes slightly; because it automates so much (for example, memory management), the runtime makes the developer's experience very simple, especially when compared to COM as it is today. In particular, features such as reflection dramatically reduce the amount of code a developer must write in order to turn business logic into a reusable component.∙Unified programming classes The framework provides developers with a unified, object-oriented, hierarchical, and extensible set of class libraries (APIs). Currently, C++ developers use the Microsoft Foundation Classes and Java developers use the Windows Foundation Classes. The framework unifies these disparate models and gives Visual Basic and JScript programmers’ access to class libraries as well. By creating a common set of APIs across all programming languages, the common language runtime enables cross-language inheritance, error handling, and debugging.All programming languages, from JScript to C++, have similar access to the framework and developers are free to choose the language that they want to use.∙ builds on the programming classes of the .NET Framework, providing a Web application model with a set of controls and infrastructure that make it simple to build ASP Web applications. includes a set of controls that encapsulate common HTML user interface elements, such as text boxes and drop-down menus. These controls run on the Web server, however, and push their user interface as HTML to the browser. On the server, the controls expose an object-oriented programming model that brings the richness of object-oriented programming to the Web developer. also provides infrastructure services, such as session state management and process recycling, which further reduce theamount of code a developer must write and increase application reliability. In addition, uses these same concepts to enable developers to deliver software as a service. Using XML Web services features, developers can write their business logic and use the infrastructure to deliver that service via SOAP.DATA CONNECTIONIntroductionThe top of the stack is the API or object library layer. Applications connect to Microsoft® SQL Server through either API functions or interfaces exposed by an object library. Examples of APIs used to access SQL Server include ODBC and DB-Library. Examples of object libraries used to access SQL Server include OLE DB, ADO, and . Because ADO ultimately uses OLE DB to communicate with the server, there are really just two object libraries commonly used by Windows applications to communicate with SQL Server: OLE DB and . Connecting through ADO or is certainly more common than doing so over ODBC (although SQL Server's Query Analyzer and Enterprise Manager Still connect over ODBC), so I'll discuss the client-side of SQL Server's connection architecture in terms of ADO/OLE DB and . Most apps these days get to SQL Server by way of an object library rather than ODBC or something similar.ADO and OLE DBOLE DB clients (also known as consumers) communicate with servers and other back-ends by means of a client-side provider. This provider is a set of one or more COM components that translate application requests into network interposes communication (IPC) requests. In the case of SQL Server, the OLE DB provider that is most commonly used is SQLOLEDB, the Microsoft-provided OLE DB provider for SQL Server. SQLOLEDB comes with SQL Server and is installed as part of the Microsoft Data Access Components (MDAC) stack.Applications that communicate with SQL Server using ADO do so by first establishing a connection to the server using a Connection object. ADO's Connectionobject accepts a connection string that specifies the OLE DB provider to be used as well as the parameters to pass to it. You'll see "SQLOLEDB" in this string if an app is connecting to SQL Server using the SQLOLEDB provider.It's also possible for an ADO application to connect over ODBC to SQL Server. To do this, the app uses the OLE DB provider for ODBC and specifies an ODBC data source that references the target SQL Server in its connection string. In this scenario, the application communicates with OLE DB, and the OLE DB provider for ODBC makes the appropriate ODBC API calls to talk to SQL Server. applications typically connect to SQL Server using the .NET Framework Data Provider for SQL Server. This native provider allows objects to communicate directly with SQL Server. Typically, an application uses a SqlConnection object to establish a connection, and then uses a SqlCommand object to send commands to the server and receive results back from it. The SqlDataAdapter and SqlDataReader classes are typically used in conjunction with SqlCommand to interact with SQL Server from managed code applications.By making use of the OleDbConnection class, applications can also use the SQLOLEDB OLE DB provider to interact with SQL Server. And they can access SQL Server by way of ODBC through the OdbcConnection class. So, from managed code alone, you have three distinct ways of accessing SQL Server from an application. This is good to know from a troubleshooting standpoint because it can help you isolate connection-related problems you encounter to a particular data access layer or library.Client-Side Net-LibrariesThe next layer down in the stack is the Net-Library. A Net-Library provides the conduit between the API or object library an application uses to communicate with SQL Server and the networking protocols used to exchange data with the network. SQL Server provides Net-Libraries for all major networking protocols. These libraries transparently handle sending requests from the client to the SQL Server and returningthe server's responses to the client. You can configure which Net-Libraries are available on a particular client using SQL Server's Client Network Utility. Supported client-side protocols include TCP/IP, Named Pipes, Multiprotocol (RPC), and a few others.One Net-Library that's worth special mention here is the shared memory Net-Library. As the name suggests, this Net-Library uses Windows' shared memory facility to communicate between a SQL Server client and server. Naturally, this means that the client and server must reside on the same physical machine.Because it is able to bypass the physical network stack, the shared memory Net-Library can be considerably faster than other Net-Libraries. Access to the shared memory region is protected by synchronization objects, so the speed of the communication between the client and server is constrained mainly by Windows' ability to signal and unsigned kernel objects and processes' ability to copy data to and from the shared memory region.You can indicate that the shared memory Net-Library should be used by specifying either a period or (local) as your machine name when connecting. You can also prefix your machine\instance name with loc:when connecting to indicate that you want to use the shared memory Net-Library.Understand that, even when connecting to a SQL Server on the same machine, the shared memory Net-Library is not necessarily your best connection option. The directness of the connection between the client and server can limit its scalability in some situations. As with other elements in an application's overall architecture, you should always thoroughly test a given technology solution before assuming that it scales well or is faster than alternate approaches.ConnectionsWhen a client connects, SQL Server's user mode scheduler (UMS) component assigns it to a particular scheduler. At startup, SQL Server creates a separate UMS scheduler for each CPU on the system. As clients connect to the server, they are assigned to the scheduler with the fewest number of connections. Once connected, aclient never changes schedulers—it will remain on its assigned scheduler until it disconnects.This has important implications for applications that establish multiple connections to the server. If an application is poorly designed or does not evenly distribute work across its connections, it's possible for the app to cause needless contention for CPU resources between some of its connections, while others remain virtually idle.Say, for example, that at application establishes four connections to SQL Server that is running on a machine with two processors and that connections 1 and 3 end up on processor 0, while connections 2 and 4 end up on processor 1. If the lion's share of the app's work is carried out over connections 1 and 3, they will contend for CPU 0 while CPU 1 might remain virtually idle. In this situation, there's nothing the app can do but disconnect/reconnect some of its connections and hope that connections 1 and 3 end up on different CPUs (there's no way to specify processor affinity when connecting) or redistribute its workload across its connections such that they are more balanced. The latter is, of course, far preferable to the former.Connection MemorySQL Server sets aside three packet buffers for every connection made from a client. Each buffer is sized according to the default network packet size specified by the sp_configure stored procedure. If the default network packet size is less than 8KB, the memory for these packets comes from SQL Server's buffer pool. If it's 8KB or larger, the memory is allocated from SQL Server's MemToLeave region.It's worth noting that the default network packet size for the .NET Framework Data Provider for SQL Server is 8KB, so the buffers associated with managed code client connections typically come from SQL Server's MemToLeave region. This contrasts with classic ADO applications, where the default packet size is 4KB, and the buffers are allocated form the SQL Server buffer pool.EventsOnce connected, client requests typically fall into one of two broad categories: language events and remote procedure calls. Although there are certainly others, most requests from a SQL Server client to a server consist of one of these two types. A language event is a batch of T-SQL sent from the client to the server. For example, if you call the Execute method of an ADO Command object whose CommandText property is set to a T-SQL query and whose CommandType property is set to adCmdText, the query is submitted to the server as a language event. Likewise, if you set CommandType to adCmdTable and call the Execute method, ADO will generate an internal query that selects all the columns in the table identified by the CommandText property and submit it to the server as a language event. On the other hand, if you set CommandType to adStoredProc, calling Execute will cause ADO to submit a remote procedure call request to the server to execute the stored procedure listed in the CommandText property.Why do you care about whether you're submitting requests to the server as language events or RPCs? You care because RPCs, generally speaking, perform better, especially when you're repeatedly calling the same query with different filter values. Although SQL Server can auto-parameterize plain language event requests, its ability to do so is pretty limited. It will not attempt to auto-parameterize certain types of queries at all. This can cause different executions of what is essentially the same query to incur the cost of plan compilation on the server simply because they filter on different values. Quite often, this is not what you want—you want to compile a new plan for the first execution of a query, then reuse the plan for subsequent executions that happen to feature different parameters.An RPC, on the other hand, encourages plan reuse by explicitly parameter zing a query rather than relying on the server to do it. A single plan is generated for the first execution of the procedure, and subsequent executions automatically reuse it, even if they supply different values for the parameters. Calling a stored procedure using an RPC versus doing so through a language event not only saves the execution time and CPU resources required for plan compilation, it also makes better use ofSQL Server's memory resources because it avoids wasting memory on redundant execution plans.This is the same reason that sp_executesql is generally preferred to EXEC() when executing dynamic T-SQL. Sp_executesql works by creating a stored procedure using the specified query, then calling it using the supplied parameters. Unlike EXEC(), sp_executesql provides a mechanism that allows you to parameterize dynamic T-SQL and encourage plan reuse. A dynamic query that is executed using sp_executesql has a much better chance of avoiding unnecessary compilation and resource costs than one ran using EXEC().TDSRPCs, language events, and other types of requests sent from a client to SQL Server are formatted into a SQL Server-specific data format known as Tabular Data Stream (TDS). TDS is the "language" spoken between SQL Server clients and servers. Its exact format is no longer documented, but a client must speak TDS if it wishes to communicate with SQL Server.Currently, SQL Server supports three versions of TDS: TDS 8.0 (for SQL 2000 clients), TDS 7.0 (for SQL Server 7.0 clients), and TDS 4.2 (for SQL Server 4.2, 6.0, and 6.5 clients). The only version that completely supports all SQL Server 2000 features is TDS 8.0. The others are maintained for backward compatibility.Server-Side Net-LibrariesOn the server side, client requests are initially received by listeners SQL Server sets up to listen on particular networking protocols. These listeners consist of networking libraries on the server and the server-side Net-Libraries that provide a conduit between them and the server. You can configure the protocols on which the server listens using the Server Network Utility. Except when dealing with clusters, SQL Servers support the same range of networking protocols as is supported by clients. For clustered SQL Servers, only TCP/IP and Named Pipes are available.SQL Server sets up one thread per networking protocol on which it listens for client requests, and uses Windows' I/O completion port mechanism to wait for and process requests efficiently. As TDS packets are received from the network, the Net-Library listener reassembles them into their original client requests and passes them on to SQL Server's command-processing layer, Open Data Services (ODS).Returning Results to the ClientWhen the server is ready to return results for a particular client request, it uses the same network stack over which the request was initially received. It sends results over the server-side Net-Library to the appropriate networking protocol, and these, in turn, are sent back across the network to the client in TDS format.On the client-side, the TDS packets received from the server are reassembled from the IPC layer by the client-side Net-Library, and then forwarded on to the API or object library that initiated the request.Putting It All TogetherDespite all the pieces involved, the roundtrip between a SQL Server client and server can be quite fast—sub-second response time is not unusual at all, especially when working with the shared memory Net-Library. There are several data points here that are worth keeping in mind as you build and tune your own SQL Server client applications:∙If your app runs on the same machine as your SQL Server, consider using the shared memory Net-Library if you aren't already. Shared memory Net-Library-based connections are often considerably faster than other types of connections. Keep in mind what I said earlier, though: always thoroughly test a solution and compare it with viable alternatives before assuming that it is inherently better or faster. The proof is in the pudding.∙Because a client is assigned to a particular UMS scheduler when it first connects and will not leave that scheduler until it disconnects, it's important to ensure that an application's workload is balanced across the connections itestablishes to the server. Unbalanced workloads can cause unnecessary CPU contention and suboptimal resource usage.∙The default network packet size you configure on the server and that clients specify when connecting directly affects how much memory they require on the server and the pool from which it is allocated. Keep this in mind as you configure servers for scalability and speed. Also keep in mind that, by default, apps will have a larger network packet size than ADO apps.∙Generally speaking, you should prefer RPCs to language events when sending requests to the server. Set the appropriate properties in the ADO or objects you're using to facilitate this.∙When executing dynamic T-SQL, use sp_executesql rather than EXEC() when possible. About the only time this isn't possible is when using EXEC()'s ability to concatenate query fragments into dynamic query strings that exceed what can be stored in a single local variable (a rare situation).∙When you run into client-side problems that you suspect may have to do with the object library or API you're using to reach the server, one troubleshooting technique you can use is to change the client-side mechanism you're using so that you can isolate the problem to a particular component. For example, let's say that you upgrade MDAC and begin seeing 17805 errors in your SQL Server error log indicating that malformed TDS packets are arriving from a client-side ADO application. You might try switching the app to use the OLE DB provider for ODBC, if you can do so without much trouble, to see whether the problem is related to the SQLOLEDB provider in some way. Conversely, if your ADO-based app has been connecting over ODBC, you might switch to SQLOLEDB to see if that remedies the problem or at least helps you narrow the scope.∙Along these same lines, it sometimes makes sense to change out the Net-Library you're using when troubleshooting connection-related problems.If you're using TCP/IP, perhaps Named Pipes would be worth trying. For example, if you're running into an issue with your DHCP server and don't havea valid IP address, you won't be able to connect to SQL Server using TCP/IP.By switching to Named Pipes, you can quickly isolate the problem to something specific to TCP/IP. On the other hand, if you switch Net Libraries and still have the same problem, you can probably rule out Net-Library-specific issues. Perhaps the server is down or a piece of the network infrastructure between you and the server is not functioning properly.If nothing else, being able to easily change the Net-Library an app uses without having to change the app itself gives you a tool for helping isolate problems. Even if a particular Net-Library isn't viable for you in the long term, temporarily switching a client to use it can help narrow down where a connection-related issue resides.Introduction to information management system of the hotelPurpose of this project are: universal access to computer technology, the traditional hotel management technology does not suit the needs of the contemporary development of hotel and guesthouse accommodation, hotel management to keep the guests one of the major factors. Hotel business links related to the work of more broad, the hotel is no longer only the traditional accommodation and settlement, but contains a wider range of services. As a service industry, from the guests scheduled to stay at the hotel registration until you check out, if you can provide fast and convenient service to guests, you will give guests a better feeling, so that you can enhance the rate of second glance of the hotel. Hotel information management system is in such demand.This project is mainly to solve daily basic requirements of hotels involved in the management of information, the goal is to make the administrator a convenient, speedy and efficient room on the Web site management, reservations, check out business. This site includes basic information management staff, rooms basic information management, reservation management, room unsubscribe management, sales management, and other important modules..NET简介.NET 框架.NET Framework 是用于生成、部署和运行 XML Web services 和应用程序的多语言环境。

外文翻译范文

外文翻译范文

百度文库 - 好好学习,天天向上-1本科毕业论文外文文献及译文文献、资料题目: Measurements and Predictionsof Steady-State and Transient Stress Distributionsin a Diesel Engine Cylinder Head文献、资料来源:SAE 文献、资料发表日期:院 (部):机电工程学院专 业:班 级:姓 名:学 号:指导教师:完成日期:外文文献:Measurements and Predictions of Steady-State and Transient Stress Distributions in a Diesel Engine Cylinder Head ABSTRACTA combined experimental and analytical approach was followed in this work to study stress distributions and causes of failure in diesel cylinder heads under steady-state and transient operation. Experimental studies were conducted first to measure temperatures, heat fluxes and stresses under a series of steady-state operating conditions. Furthermore, by placing high temperature strain gages within the thermal penetration depth of the cylinder head, the effect of thermal shock loading under rapid transients was studied. A comparison of our steady-state and transient measurements suggests that the steady-state temperature gradients and the level of temperatures are the primary causes of thermal fatigue in cast-iron cylinder heads. Subsequently, a finite element analysis was conducted to predict the detailed steady-state temperature and stress distributions within the cylinder head. A comparison of the predicted steady-state temperatures and stresses compared well with our measurements. Furthermore, the predicted location of the crack initiation point correlated well with experimental observations. This suggests that a validated steady-state FEM stress analysis can play a very effective role in the rapid prototyping of cast-iron cylinder heads.INTRODUCTIONHeavy-duty diesel engine cylinder heads experience severe thermal and mechanical loading, under both steady-state and transient engine operation. Consequently, cylinder head design is very sophisticated as it needs to house complex cooling passages for ensuring compliance with thermal stresses, while providing sufficient mechanical strength to withstand combustion pressures, and yet accommodating intake and exhaust valves and ports, and the fuel injector. As a result of design, weight and manufacturing compromises, cylinder heads often fail in operation due to cracks that are initiated due to-1thermal fatigue in regions where cooling is limited, such as in the narrow bridge between valves, or around the exhaust valve seat.A number of studies have so far been conducted to develop analytical methodologies suitable for rapid design and virtual prototyping of cylinder heads. The finite element method has been the foundation of many of the analyses that predict the thermal and stress fields within the cylinder head. However, the accuracy of such analyses critically depends on our understanding of the problem, and the accuracy of the boundary conditions used in the formulation. Thermal stresses are induced by any of the following causes:Temperature gradients under steady-state operation, including the effects of cyclic temperature changes in the combustion chamber wallAn increase in the mean temperature of a component, which affects the expansion and distortion characteristics, thus inducing stressesThermal shock loading resulting from a sudden change in speed or load during transients, which change the rate of heat flux from the gas to the cylinder head.Due to the inherent difficulties in measuring stress fields near the critical regions on the firedeck surface, especially under transient conditions, limited sets of measurements that can shed light on the problem have been reported .A numerical study of thermal shock calculations by Keribar and Morel has shown that thermal waves propagate into components during engine transients, with the steepness of the front depending on material thermal properties. While for a ceramic component severe shock loads can cause surface compressive stresses to overshoot final steady-state values, the effect was not pronounced in higher conductivity materials. In order to validate this analytical finding, and attribute appropriately causes of failure in cast-iron cylinder heads, a combined experimental and analytical approach is followed here to study stress distributions under steady-state and transient operation.Experimental studies are conducted first to measure temperatures, heat fluxes and stresses under a series of steady-state and transient operating conditions. Both biaxial and-2uni-axial high temperature strain gages have been inserted within the thermal penetration depth of a diesel engine cylinder head. The strain gage insertion beneath the surface of the firedeck ensures the durability and reliability of the sensor. At the same time, the placement within the thermal penetration depth allows for studying the effect of thermal shock loading under rapid transients, and for contrasting those measurements with corresponding steady-state magnitudes. Subsequently, a finite element analysis is conducted to predict the steady-state temperature and stress distributions within the cylinder head. Predictions are compared with measurements, and the potential of the method to predict high stress regions that could lead to crack initiation is explored. EXPERIMENTAL MEASUREMENTSEXPERIMENTAL SETUP – Temperature, heat flux and stress measurements were acquired on a six-cylinder, naturally-aspirated, direct-injection, Hyundai diesel engine, primarily used in bus applications. The primary specifications of the engine are reported in Table 1.TEMPERATURE AND HEAT FLUX SENSORS – A total of 8 steady-state temperature and heat flux probes were installed around the intake and exhaust valve seats of cylinders #2 and #6. The probe tips were mounted at a depth of 1.0 mm beneath the firedeck surface, at the locations shown in Figs. 1 and 2. A schematic diagram showing the construction of the temperature and heat flux probe is shown in Fig. 3. The probe was made of Ktype thermocouples. A near-surface (1.0 mm beneath the firedeck) and an in-depth junction (4.0 mm beneath the surface) make it possible to calculate heat flux. To enhance the sensitivity of the junctions, a thin (1mm thickness), circular copper plate was welded at the tip of the sensor. Temperature and heat flux data were acquired every 1 second, under full load, over a speed range from 1000 rpm to 2500 rpm, every 500 rpm.Table 1. Specification of the test engine118 X 115 mm-3Ignition Order 1-5-3-6-2-4Maximum Torque 475 N·m @1500rpmMaximum Power123 kW @ 2200 rpmFigure 1. Temperature and heat flux measuring points on the firedeck HIGH TEMPERATURE ST RAIN GAGES –For measuring stress within engine cylinder heads, especially near the gas-side surface, strain gages with high temperature durability are needed. A special procedure has been developed in this work for constructing a strain gage sensor plug (see Fig. 4) that is suitable for such measurements. The details of the sensor selection, attachment in the instrumentation plug, and verification of its operation are described next.Figure 2. Location of sensor on the firedeckFigure 3. Schematic diagram of temperature and heat flux sensor-45Figure 4. Schematic diagram illustrating strain gage sensor and critical dimensionsTwo types of high temperature strain gages (120Ωand 350Ω) were used. Thespecifications of the sensors made by Micromeasurement Co. are described in Table 2. According to the manufacturer, the response time of the strain gages was 300 kHz μs). In case of the 120Ωstrain gage, the strain gage was coated with high temperature resistance bond after attachment to the inside surface of a cup-shaped plug. Then, the strain gage was heated in a microwave oven for 3 hours. After cooling to ambient temperature, the strain gage was recoated and re-heated at 150°C for 3 more hours. In case of the 350Ωstrain gage, heating was applied for a grand total of 4 hours at a temperature of 175°C.Table 2. Specifications of high temperature strain gagesGage Type WA-06-062TT-120 WA-06- 60WT-350Resistance inΩ±% ±%Lot Number D-A38AD73 K44FD121Gage FactorAt 75°F±% ±%Range Cont.Use-75 to 205°C -269 to 290°CShortUse-195 to 260°C 370°CFollowing construction of the instrumentation plug, its sensing behavior was explored. The plug temperature was varied by exposing it to a torch, and recorded via an attached-thermocouple. Corresponding strain readings were also recorded. The experimentally measured strain versus temperature characteristic was compared to the one published by the manufacturer, and used as the basis for validating the sensor plug behavior.Figure 5. A photograph of high temperature strain gageThe highest component temperatures, and hence thermally- induced stresses are experienced at the combustion chamber surface. While it is desirable to measure stresses on the surface, sensors mounted flush with the surface have a very short life. In order to ensure the durability and reliability of the strain gage sensor plug, it was inserted 1.5 mm beneath the surface. This location was still within the penetration depth of thermal transients originating at the gas-side surface. Thus, it allowed studying the effect of thermal shock loading under rapid transients. A total of 4 strain gage sensor plugs were inserted near the intake and exhaust valve seats of cylinder #2 and #4 (see Fig. 6 ).Figure 6. Schematic diagram of strain gage positionThe stain gages inserted in cylinder #4 were of the biaxial type, measuring strain in the x and y directions, as defined in Fig. 7. The strain gages inserted in cylinder #2 were of the uni-axial type, measuring strain in a 45°axis. Since strain gage signals can be highly affected by even minute lead wire movement, care was exercised to attach them firmly to the engine head. Steady-state stresses were measured as speed was varied from 1000 rpm to 2000 rpm, in increments of 250 rpm, under full load. Transient stress measurements were also acquired every seconds, while load was cycled between 0 and-6100% for several engine speeds.Figure 7. Stress measurement directionsTEMPERATURE AND HEAT FLUX MEASUREMENTS – Figures 8 and 9 show the steady-state temperatures measured at the four locations within the firedeck of cylinders #2 and #6, respectively. In all cases, the measured temperatures increase linearly with respect to engine speed. Increasing speed allows less time for heat transfer to the coolant between combustion events. The highest temperature values are recorded at location B, followed by those at A, C, and D. It should be noted that location B is between the injector nozzle hole and the exhaust valve. Since there is no coolant passage near that region, this explains why location B reaches the highest temperature of the four locations investigated. On the other hand, location D experiences the lowest temperature as it is exposed to significant forced cooling from the adjacent coolant passage and from the induced fresh air.Figure 8. Steady-state wall temperatures in cylinder #2 over a range of speeds-78Figure 9. Steady-state wall temperatures in cylinder #6 over a range of speedsFigures 10 and 11 show the corresponding steady-state heat fluxes computed at thesame locations within cylinders #2 and #6, respectively. Again, heat flux increases linearly with engine speed. The heat flux magnitudes are higher for positions B and C, located around the exhaust valve seat, compared to those at A and D, located around the intake valve seat. Note that as speed is increasing, different locations experience different rates of increase of heat flux, a fact that is attributed to differences in turbulent gas motion and coolant flow patterns. When the heat flux rates in cylinders #2 and #6 are compared (see Figs. 10 and 11), it can be noticed that the former experiences higher heat flux rates than the latter. This is attributed to the fact that the coolant flows first around cylinder #2; by the time it reaches cylinder #6, the coolant has picked up some heat and its temperature gradually rises, thus reducing the potential for heat transfer from cylinder #6. As a result of the higher heat fluxes, the firedeck temperatures around cylinder #2 are lower (by about 10 °C) than those around cylinder #6 that is located on the coolant outlet side.STRESS MEASUREMENTS –In order to be able to isolate the effect of pre-loading on the total stress measurements recorded in a fired engine by the various strain gages, stress measurements were taken during the engine assembly process. Measurements were taken at the four strain gages following the tightening of each head bolt. The initial stress variation is shown in Fig. 12. While the tightening of different bolts produced different amounts of tension and compression at the measurement location, no consistent pattern was revealed by the measurements. However, it is important to notice that pre-loading produced a negligible stress (within ±5MPa) at the measurement-locations, irrespective of directions.Figure 10. Steady-state heat fluxes in cylinder #2 over a range of speedsFigure 11. Steady-state heat fluxes in cylinder #6 over a range of speedsFigure 12. Effect of bolt tightening on pre-loading stressFigure 13 shows the steady-state stresses recorded by the bi-axial strain gages at intake and exhaust valve locations of cylinder #4, as well as the stresses recorded by the-9uni-axial strain gages at intake and exhaust valve locations of cylinder #2. The measurements were taken over a range of engine speeds and at full load, . conditions that would produce the maximum stress at each speed. It must be noted that as engine speed is increased towards the maximum torque speed (1500 rpm), the measured stresses increase (or decrease) at a faster rate. Beyond the maximum torque speed, the stress variation is slight. Both tensile and compressive stresses appear simultaneously at the different locations, as shown in Fig. 13, thus indicating the complex character of the stress field.Figure 13. Steady-state stress variation with respect to engine speed at full load The measured stress near the exhaust valve seat has negative values (x, y directions), indicating a compression effect. This could have been produced from a tendency of high temperature regions (such non-adequately cooled regions around the injector and the valve bridge) to expand, while subjected to mechanical constraints. As a result, the rest of the firedeck expands more in relative terms, as suggested by the tensile stresses experienced at the other measurement locations. It must also be noted that, at the various speeds, the absolute magnitude of the stresses near the exhaust valve are two to three times larger than those at the intake valve, for either cylinder #2 or #4. This correlates well with the two to three times higher heat flux measured on the exhaust valve seat compared to the corresponding heat flux on the intake valve seat (refer to results for locations B and A in Figs. 10 and 11).Figure 14. Transient stress variation in x and y directions at exhaust valve of cylinder #4Figure 15. Transient stress variation in x and y directions at intake valve of cylinder #4A transient test schedule has also been developed in order to assess the effect of thermal shock loading on the stresses measured at the same locations where steady-state measurements were reported. The schedule followed engine operation from cold start to firing under a series of speeds and loads. Figures 14 to 16 show the transient stresses recorded by the bi-axial and uni-axial strain gages at the instrumented locations near the exhaust and intake valves of cylinders #4 and #2. All figures indicate the same general characteristics. The period from A toB indicates the equilibrium state with coolant at room temperature and no thermally induced stresses. Upon turning on the engine (state B), a step change in stress level was observed at all measurement locations, except for the 45°direction around the intake valve seat of cylinder # 2 (see fig. 16). From B to C, temperatures and thermal stresses were stabilized while the engine was idling at a speed of 700 rpm. The stresses continued to increase (or decrease) smoothly, as speed was gradually increased from 700 rpm to 1000 rpm (C to D).Figure 16. Transient stress variation in 45° directions at exhaust and intake valves of cylinder #2 Following engine warm-up (from state D on), a cyclic test pattern was imposed. Speed was increased from 1000 rpm to 2000 rpm in increments of 250 rpm, while the load was cycled between full load and no load at each test speed. The measured stresses followed a cyclic pattern as a result of the imposed large swings in gas temperatures and gas-side surface temperatures. The thermal shock loading experienced by the cylinder head during this severe transient is evident. It should be noted, however, that the absolute magnitudes of the stresses recorded at any instant during the transient exceed only marginally the levels that would correspond to steady-state operation under each of those conditions. This is attributed to the fact that thermal shock waves penetrate fast into the cast-iron cylinder head. Following the cyclic operation, the engine was turned-off (state F), and an abrupt change in stress levels was recorded. However, some residual stresses remained after shut-off, which required more than 7 hours to be relaxed. COMPUTATIONAL PREDICTIONSA three-dimensional numerical analysis based on the finite element method (FEM) can be used to predict the detailed steady-state temperature and stress distributions within the cylinder head. A synopsis of the FEM model, its validation against our measurements, and predictions using the model are reported below.FEM ANALYSIS – A three-dimensional finite element model of the cylinder head and block was composed, as shown in Fig. 17. Most of the grid elements are isoparametric solid brick with the rest of them being prism elements. A gasket model, represented as one row of elements has been inserted between the head and block models.A total of 12,156 nodes points and 7,803 elements were employed to described the FEMmodel. The cylinder head and block were made of cast-iron, while the gasket was assumed to be an indium composite material. Material properties are summarized in Tables 3 and 4. Steady-state, heat transfer and stress analyses were conducted using the commercial codes NISA II (solver) and DISPLAY III (pre and post-processor). The heat transfer analysis was conducted first. Subsequently, the heat transfer results were used to perform the stress analysis.Figure 17. 3-D FEM model of head and blockTable 3. Properties of cast-iron Table 4. Properties of indium composite materialThermal conductivity, k [W/m·K] Thermal conductivity, k [W/m·K]Young’s Modulus, E [GPa] Young’s Modulus, E [GPa]Poisson’s Ratio, Poisson’s Ratio,Thermal Expansion Coefficient, [1/K] x 10-6 Thermal ExpansionCoefficient, [1/K]x 10-7specified. The cyclic-mean values of the in-cylinder gas-to-wall heat transfer coefficient and bulk gas temperature were obtained from the comprehensive thermodynamic cycle simulation developed by Assanis and Heywood. The boundary conditions at the intake and exhaust port were obtained based on experimental correlations reported by Annand and Hires. Coolant side boundary conditions were based on values reported in the literature. The lower values for the coolant temperature and heat transfer coefficient wereused in regions of lower coolant velocity, such as in between cylinder bores.For the stress analysis, only thermal stresses were considered. As mechanical boundary conditions, two points were fixed (∆x=∆y=∆z=0) inside the head bolt hole, and the rigid link method was applied. The gasket contact surface was assumed to be unconstrained.Table 5. Thermal boundary conditionspredictions at selected points of the thermal and stress fields were compared with measurements recorded at the same points. As shown in Fig. 18, measured and predicted steady-state wall temperatures compare favorably over a range of engine speeds, both in magnitude and trend.Comparisons between measured and predicted steadystate stresses are shown in Figs.19 and 20. While the agreement in trend is satisfactory, some differences in magnitude are observed. The discrepancies can be attributed to the following reasons. First, experimental data include the effects of both thermal loading and combustion pressure. On the other hand, only the thermal effect is considered in FEM analysis. Nevertheless,the relatively small difference in magnitudes confirms that the effect of mechanical stresses is relatively small. Second, the stiffness of the firedeck may have been altered due to the strain gage insertion process. Third, the FEM analysis has not accounted for cylinder-by-cylinder variation in boundary conditions due to factors such as manifold gas dynamics, coolant maldistribution, etc. Overall, it is concluded that the FEM model with the applied boundary conditions has the potential to capture the thermal and stress filed within the cylinder head with acceptable accuracy.Figure 18. Comparison between measured and predicted steady-state wall temperatures over a rangeof engine speedsFigure 19. Comparison between measured and predicted steady-state stresses near the intake valve,over a range of engine speedsFigure 20. Comparison between measured and predicted steady-state stresses near the exhaust valve,over a range of engine speedsSTEADY-STATE PREDICTIONS OF THERMAL AND STRESS DISTRIBUTIONS –FEM predictions of the steady-state temperature and stress distributions in the firedeck are shown in Fig. 21 for a range of engine speeds at full load. The isotherm plots a-d, on the left hand side Fig. 21, indicate that the region of the firedeck in the vicinity of the exhaust valve seat experiences considerably higher temperatures (80 °C to 100 °C) than the rest of the firedeck. The maximum temperature varies from 232 °C at 1000 rpm to 312 °C at 2500 rpm as a result of increasing mean gas temperature and heat transfer coefficient with increased engine speed. Notice also that as speed is increasing, the hot region propagates from the exhaust valve side to the intake valve side. Outside the firedeck, the cylinder head face experiences temperatures close to the coolant temperature (around 80 °C), independent of speed.It is important to observe that the largest temperature gradients occur between the exhaust valve seat and the injector nozzle hole, and the valve bridge between the two valves. At the two lower engine speeds, the injector nozzle hole and the valve bridge are surrounded by uniformly lower temperatures. However, the propagation of the hot front with increasing speed results in an asymmetric exposure of those critical regions to hot and cold temperatures. It is therefore anticipated that the highest thermal stresses should be concentrated on either the injector hole or the valve bridge region, as thermal stress linearly depends on temperature gradient.(a) Predicted isotherms at 1000 rpm;min = 80 °C, max = 232 °C, increment = 10.1 °C(e) Predicted iso-stress contours at 1000 rpm;min = 3 MPa, max = 251 MPa, increment =MPa(b) Predicted isotherms at 1500 rpm;min = 80 °C, max = 263 °C, increment =12.2 °C(f) Predicted iso-stress contours at 1500 rpm;min = 3 MPa, max = 299 MPa, increment =MPa(c) Predicted isotherms at 2000 rpm;min = 80 °C, max = 287 °C, increment = 13.8 °C(g) Predicted iso-stress contours at 2000 rpm;min = 5 MPa, max = 354 MPa, increment =MPa(d) Predicted isotherms at 2500 rpm;min = 80 °C, max = 312 °C, increment = 15.5 °C(h) Predicted iso-stress contours at 2500 rpm;min = 5 MPa, max = 405 MPa, increment =Plots e-h, on the right hand side of Fig. 21, show the predicted thermal stress distributions within the firedeck as Von Mises stress. In general, higher levels of stresses are experienced as speed, gas and wall temperatures increase, consistent with corresponding predictions of the thermal field in the firedeck. Notice however that at every speed, the maximum stress values occur where the maximum temperature gradients (and not where the maximum temperatures) are found. Hence, the location of the maximum thermal stresses is indeed around the injector nozzle hole and the valve bridge region, as suggested from our predictions of the temperature gradients.The maximum stress at those critical locations increases from 251 MPa to 405 MPa, as speed increases from 1000 rpm to 2500 rpm. Given that the yield stress of heat treated cast-iron is around 350 MPa this suggests that regions of the cylinder head may be prone to plastic deformation at conditions over 2,000 rpm and full load. Under severe thermal loading, this plastic deformation would first lead to crack initiation around the nozzle hole and valve bridge. Indeed, Fig. 22 shows that an engine operated under similar conditions developed a crack in the cylinder head firedeck in the region between the injector nozzle hole and the exhaust valve seat, thus validating the numerical predictions. CONCLUSIONSA combined experimental and analytical approach was followed in this work to study stress distributions and causes of failure in diesel cylinder heads under steady-state and transient operation. Experimental studies were conducted first to measure temperatures, heat fluxes and stresses under a series of steady-state and transient operating conditions. Subsequently, a finite element analysis was conducted to predict the detailed steady-state temperature and stress distributions within the cylinder head. The following conclusions can be drawn from our study:Figure 22. Photograph of a typical crack initiation point1. Thermal shock loading plays a role in thermal fatigue, along with steady-state temperature gradients and the level of temperatures. When the engine is turned on or off ,and during periods of changing load at a given speed, the stress level changes significantly. However, a comparison of our steady-state and transient measurements indicates that stresses recorded at any instant during a severe transient are only marginally higher than stresses that would correspond to steady-state operation under each of those conditions. This is attributed to the fact that thermal shock waves penetrate fast into the cast-iron cylinder head.2. As engine speed is increased towards the maximum torque speed, the measured steady-state stresses increase or decrease at a faster rate. Beyond the maximum torque speed, the stress variation is slight. The largest temperature gradients occur between the injector nozzle hole and the exhaust valve seat, and valve bridge between two valves. The location of the maximum thermal stress is around the injector nozzle hole and valve bridge region as suggested from prediction of temperature gradients. Hence, under severe thermal loading, the plastic deformation would first lead to crack initiation around the injector nozzle hole and valve bridge.3. A comparison of the predicted steady-state temperatures and stresses compared well with our measurements. Furthermore, the predicted location of the crack initiation point correlated well with experimental observations. This suggests that a validated steady-state FEM stress analysis can play a very effective role in the rapid prototyping of cast-iron cylinder heads.。

五分钟搞定5000字外文文献翻译

五分钟搞定5000字外文文献翻译

五分钟搞定5000字-外文文献翻译,你想要的工具都在这里。【大四的时候写毕业论文老师就要求得翻译外文文献并写入论文】
五分钟搞定5000字-外文文献翻译
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在科研过程中阅读翻译外文文献是一个非常重要的环节,许多领域高水平的文献都是外文文献,借鉴一些外文文献翻译的经验是非常必要的。由于特殊原因我翻译外文文献的机会比较多,慢慢地就发现了外文文献翻译过程中的三大利器:Google“翻译”频道、金山词霸(完整版本)和CNKI“翻译助手"。
比如说“电磁感应透明效应”这个词汇你不知道他怎么翻译,
首先你可以在CNKI里查中文的,根据它们的关键词中英文对照来做,一般比较准确。
在此主要是说在google里怎么知道这个翻译意思。大家应该都有词典吧,按中国人的办法,把一个一个词分着查出来,敲到google里,你的这种翻译一般不太准,当然你需要验证是否准确了,这下看着吧,把你的那支离破碎的翻译在google里搜索,你能看到许多相关的文献或资料,大家都不是笨蛋,看看,也就能找到最精确的翻译了,纯西式的!我就是这么用的。
3、网路版金山词霸(不到1M):/6946901637944806
翻译时的速度: பைடு நூலகம்
这里我谈的是电子版和打印版的翻译速度,按个人翻译速度看,打印版的快些,因为看电子版本一是费眼睛,二是如果我们用电脑,可能还经常时不时玩点游戏,或者整点别的,导致最终SPPEED变慢,再之电脑上一些词典(金山词霸等)在专业翻译方面也不是特别好,所以翻译效果不佳。在此本人建议大家购买清华大学编写的好像是国防工业出版社的那本《英汉科学技术词典》,基本上挺好用。再加上网站如:google CNKI翻译助手,这样我们的翻译速度会提高不少。

论文用5000字中英文翻译

论文用5000字中英文翻译

MCU DescriptionSCM is also known as micro-controller (Microcontroller Unit), commonly used letters of the acronym MCU that it was first used in industrial control. Only a single chip by the CPU chip developed from a dedicated processor. The first design is by a large number of peripherals and CPU on a chip in the computer system, smaller, more easily integrated into a complex and demanding on the volume control device which. INTEL's Z80 is the first designed in accordance with this idea processor, then on the development of microcontroller and dedicated processors have parted ways.Are 8-bit microcontroller early or 4 bits. One of the most successful is the INTEL 8031, for a simple, reliable and good performance was a lot of praise. Then developed in 8031 out of MCS51 MCU Systems. SCM systems based on this system until now are still widely used. With the increased requirements of industrial control field, began a 16-bit microcontroller, because the cost is not satisfactory but have not been very widely used. After 90 years with the great development of consumer electronics, microcontroller technology has been a huge increase. With INTEL i960 series, especially the later series of widely used ARM, 32-bit microcontroller quickly replace high-end 16-bit MCU status and enter the mainstream market. The traditional 8-bit microcontroller performances have been the rapid increase capacity increase compared to 80 the number of times. Currently, high-end 32-bit microcontroller clocked over 300MHz, the performance catching the mid-90's dedicated processor, while the average model prices fall to one U.S. dollars; the most high-end model only 10 dollars. Modern SCM systems are no longer only in the development and use of bare metal environment, a large number of proprietary embedded operating system is widely used in the full range of SCM. The handheld computers and cell phones as the core processing of high-end microcontroller can even use a dedicated Windows and Linux operating systems.SCM is more suitable than the specific processor used in embedded systems, so it was up to the application. In fact the number of SCM is the world's largest computer. Modern human life used in almost every piece of electronic and mechanical products will be integrated single chip. Phone, telephone, calculator, home appliances,electronic toys, handheld computers and computer accessories such as a mouse with a 1-2 in both the Department of SCM. Personal computer will have a large number of SCM in the work. General car with more than 40 SCM, complex industrial control systems may even have hundreds of SCM in the same time work! SCM is not only far exceeds the number of PC and other computing the sum, or even more than the number of human beingsSingle chip, also known as single-chip microcontroller, it is not complete a certain logic chips, but to a computer system integrated into a chip. Equivalent to a micro-computer, and computer than just the lack of a microcontroller I / O devices. General talk: a chip becomes a computer. Its small size, light weight, cheap, for the study, application and development of facilities provided. At the same time, learning to use the MCU is to understand the principle and structure of the computer the best choice. SCM and the computer functions internally with similar modules, such as CPU, memory, parallel bus, the same effect as well, and hard disk memory devices, and different is its performance of these components were relatively weak many of our home computer, but the price is low , usually not more than 10 yuan you can do with it ...... some control for a class is not very complicated electrical work is enough of. We are using automatic drum washing machine, smoke hood, VCD and so on appliances which could see its shadow! ...... It is primarily as a control section of the core componentsIt is an online real-time control computer, control-line is that the scene is needed is a stronger anti-jamming ability, low cost, and this is, and off-line computer (such as home PC), the main difference.Single chipMCU is through running, and can be modified. Through different procedures to achieve different functions, in particular special unique features, this is another device much effort needs to be done, some great efforts are very difficult to do. A not very complex functions if the 50's with the United States developed 74 series, or the 60's CD4000 series of these pure hardware buttoned, then the circuit must be a large PCB board! But if the United States if the 70's with a series of successful SCM market, theresult will be a drastic change! Just because you are prepared by microcomputer programs can achieve high intelligence, high efficiency and high reliability!As the microcontroller on the cost-sensitive, so now the dominant software or the lowest level assembly language, which is the lowest level in addition to more than binary machine code language, and as so low why is the use? Many high-level language has reached the level of visual programming Why is not it? The reason is simply that there is no home computer as a single chip CPU, not as hard as a mass storage device. A visualization of small high-level language program which even if only one button, will reach tens of K of size! For the home PC's hard drive in terms of nothing, but in terms of the MCU is not acceptable. SCM in the utilization of hardware resources to be very high for the job so although the original is still in the compilation of a lot of use. The same token, if the giant computer operating system and applications run up to get home PC, home PC, also can not afford to.Can be said that the twentieth century across the three "power" era, that is, the age of electricity, the electronic age and has entered into the computer age. However, this computer, usually refers to the personal computer, referred to as PC. It consists of the host, keyboard, monitor and other components. Another type of computer, most people do not know how. This computer is to give all kinds of intelligent machines single chip (also known as micro-controller). As the name suggests, this computer system took only a minimal integrated circuit, can be a simple operation and control. Because it is small, usually hidden in the charged mechanical "stomach" in. It is in the device, like the human brain plays a role, it goes wrong, the whole plant was paralyzed. Now, this microcontroller has a very broad field of use, such as smart meters, real-time industrial control, communications equipment, navigation systems, and household appliances. Once all kinds of products were using SCM, can serve to upgrade the effectiveness of products, often in the product name preceded by the adjective - "intelligent," such as intelligent washing machines. Now some technical personnel of factories or other amateur electronics developers to engage in out of certain products, not the circuit is too complicated, that function is too simple and can easily be copied. The reason may be stuck in the product did not use a microcontrolleror other programmable logic device.SCM historySCM was born in the late 20th century, 70, experienced SCM, MCU, SoC three stages.First model1.SCM the single chip microcomputer (Single Chip Microcomputer) stage, mainly seeking the best of the best single form of embedded systems architecture. "Innovation model" success, laying the SCM and general computer completely different path of development. In the open road of independent development of embedded systems, Intel Corporation contributed.2.MCU the micro-controller (Micro Controller Unit) stage, the main direction of technology development: expanding to meet the embedded applications, the target system requirements for the various peripheral circuits and interface circuits, highlight the object of intelligent control. It involves the areas associated with the object system, therefore, the development of MCU's responsibility inevitably falls on electrical, electronics manufacturers. From this point of view, Intel faded MCU development has its objective factors. In the development of MCU, the most famous manufacturers as the number of Philips Corporation.Philips company in embedded applications, its great advantage, the MCS-51 single-chip micro-computer from the rapid development of the micro-controller. Therefore, when we look back at the path of development of embedded systems, do not forget Intel and Philips in History.Embedded SystemsEmbedded system microcontroller is an independent development path, the MCU important factor in the development stage, is seeking applications to maximize the solution on the chip; Therefore, the development of dedicated single chip SoC trend of the natural form. As the microelectronics, IC design, EDA tools development, application system based on MCU SOC design have greater development. Therefore, the understanding of the microcontroller chip microcomputer can be, extended to the single-chip micro-controller applications.MCU applicationsSCM now permeate all areas of our lives, which is almost difficult to find traces of the field without SCM. Missile navigation equipment, aircraft, all types of instrument control, computer network communications and data transmission, industrial automation, real-time process control and data processing, extensive use of various smart IC card, civilian luxury car security system, video recorder, camera, fully automatic washing machine control, and program-controlled toys, electronic pet, etc., which are inseparable from the microcontroller. Not to mention the area of robot control, intelligent instruments, medical equipment was. Therefore, the MCU learning, development and application of the large number of computer applications and intelligent control of the scientists, engineers.SCM is widely used in instruments and meters, household appliances, medical equipment, aerospace, specialized equipment, intelligent management and process control fields, roughly divided into the following several areas:1. In the application of Intelligent InstrumentsSCM has a small size, low power consumption, controlling function, expansion flexibility, the advantages of miniaturization and ease of use, widely used instrument, combining different types of sensors can be realized Zhuru voltage, power, frequency, humidity, temperature, flow, speed, thickness, angle, length, hardness, elemental, physical pressure measurement. SCM makes use of digital instruments, intelligence, miniaturization, and functionality than electronic or digital circuits more powerful. Such as precision measuring equipment (power meter, oscilloscope, various analytical instrument).2. In the industrial control applicationWith the MCU can constitute a variety of control systems, data acquisition system. Such as factory assembly line of intelligent control3. In Household AppliancesCan be said that the appliances are basically using SCM, praise from the electric rice, washing machines, refrigerators, air conditioners, color TV, and other audio video equipment, to the electronic weighing equipment, varied, and omnipresent.4. In the field of computer networks and communications applicationsMCU general with modern communication interface, can be easy with the computer data communication, networking and communications in computer applications between devices had excellent material conditions, are basically all communication equipment to achieve a controlled by MCU from mobile phone, telephone, mini-program-controlled switchboards, building automated communications call system, train radio communication, to the daily work can be seen everywhere in the mobile phones, trunked mobile radio, walkie-talkies, etc..5. Microcomputer in the field of medical device applicationsSCM in the use of medical devices is also quite extensive, such as medical respirator, the various analyzers, monitors, ultrasound diagnostic equipment and hospital beds, etc. call system.6. In a variety of major appliances in the modular applicationsDesigned to achieve some special single specific function to be modular in a variety of circuit applications, without requiring the use of personnel to understand its internal structure. If music integrated single chip, seemingly simple function, miniature electronic chip in the net (the principle is different from the tape machine), you need a computer similar to the principle of the complex. Such as: music signal to digital form stored in memory (like ROM), read by the microcontroller, analog music into electrical signals (similar to the sound card).In large circuits, modular applications that greatly reduce the volume, simplifies the circuit and reduce the damage, error rate, but also easy to replace.7. Microcontroller in the application field of automotive equipmentSCM in automotive electronics is widely used, such as a vehicle engine controller, CAN bus-based Intelligent Electronic Control Engine, GPS navigation system, abs anti-lock braking system, brake system, etc..In addition, the MCU in business, finance, research, education, national defense, aerospace and other fields has a very wide range of applications.Application of six important part of learningMCU learning an important part of the six applications1, Bus:We know that a circuit is always made by the devices connected by wires, in analog circuits, the connection does not become a problem because the device is a serial relationship between the general, the device is not much connection between the , but the computer is not the same circuit, it is a microprocessor core, the device must be connected with the microprocessor, the device must be coordination between, so they need to connect on a lot, as if still analog circuit like the microprocessor and devices in the connection between the individual, the number of lines will be a little more surprising, therefore the introduction of the microprocessor bus Chong Each device Gong tong access connections, all devices 8 Shuju line all received eight public online, that is the equivalent of all devices together in parallel, but only this does not work, if there are two devices send data at the same time, a 0, a 1, then, whether the receiver received what is it? This situation is not allowed, so to be controlled by controlling the line, time-sharing the device to work at any time only one device to send data (which can have multiple devices to receive both). Device's data connection is known as the data bus, the device is called line of control all the control bus. Internal or external memory in the microcontroller and other devices have memory cells, the memory cell to be assigned addresses, you can use, distribution, of course, to address given in the form of electrical signals, and as more memory cells, so, for the address allocation The line is also more of these lines is called the address bus.2, data, address, command:The reason why these three together because of the nature of these three are the same - the number, or are a string of '0 'and '1' form the sequence. In other words, addresses, instructions are also data. Instruction: from single chip designer provides a number of commonly used instructions with mnemonic we have a strict correspondence between the developer cannot be changed by the MCU. Address: the search for MCU internal, external storage units, input and output port based on the address of the internal unit value provided by the chip designer is good, cannot be changed, the external unit can be single chip developers to decide, but there are anumber of address units is a must (see procedures for the implementation of the process).3, P0 port, P2 and P3 of the second function I use:Beginners often on the P0 port, P2 and P3 port I use the second function puzzled that the second function and have a switch between the original function of the process, or have a directive, in fact, the port the second feature is automatic, do not need instructions to convert. Such as P3.6, P3.7 respectively WR, RD signal, when the microchip processing machines external RAM or external I/O port, they are used as a second function, not as a general-purpose I/O port used, so long as a microprocessor implementation of the MOVX instruction, there will be a corresponding signal sent from the P3.6 or P3.7, no prior use of commands. In fact 'not as a general-purpose I/O port use' is also not a 'no' but (user) 'not' as a general-purpose I/O port to use. You can arrange the order of a SETB P3.7's instructions, and when the MCU execution to the instruction, the also make P3.7 into a high, but users will not do so because this is usually will cause the system to collapse.4, the program's implementation:Reduction in power after the 8051 microcontroller within the program counter (PC) in the value of 0000 ', the process is always from the 0000' units started, that is: the system must exist in ROM 0000 'this unit, and in 0000 'unit must be stored in a single instruction.5, the stack:Stack is a region, is used to store data, there is no special about the region itself is a part of internal RAM, special access to its data storage and the way that the so-called 'advanced post out backward first out ', and the stack has a special data transmission instructions that' PUSH 'and' POP ', has a special expertise in its services unit, that is, the stack pointer SP, whenever a PUSH instruction execution, SP on (in the Based on the original value) automatically add 1, whenever the implementation of a POP instruction, SP will (on the basis of the original value) automatically by 1. As the SP values can be changed with the instructions, so long as the beginning of theprocess to change the value of the SP, you can set the stack memory unit required, such as the program begins, with an MOV SP, #5FH instructions When set on the stack starting from the memory unit 60H unit. There is always the beginning of the general procedure with such a directive to set the stack pointer, because boot, SP initial value of 07H, 08H This unit from the beginning to stack next, and 08H to 1FH 8031 is the second in the region, three or four working register area, often used, this will lead to confusion of data. Different authors when writing programs, initialize the stack is not exactly the same directive, which is the author's habit. When set up the stack zone, does not mean that the region become a special memory, it can still use the same memory region as normal, but generally the programmer does not regard it as an ordinary memory used.Structure and function of the MCS-51 seriesStructure and function of the MCS-51 series one-chip computer is a name of a piece of one-chip computer series which Intel Company produces. This company introduced 8 top-grade one-chip computers of MCS-51 series in 1980 after introducing 8 one-chip computers of MCS-48 series in 1976. It belong to a lot of kinds this line of one-chip computer the chips have, such as 8051, 8031, 8751, 80C51BH, 80C31BH,etc., their basic composition, basic performance and instruction system are all the same. 8051 daily representatives- 51 serial one-chip computers.An one-chip computer system is made up of several following parts:(1) One microprocessor of 8 (CPU). (2)At slice data memory RAM (128B/256B),it use not depositing not can reading /data that write, such as result not middle of operation, final result and data wanted to show, etc. (3)Procedure memory ROM/EPROM (4KB/8KB ), is used to preserve the procedure , some initial data and form in slice. But does not take ROM/EPROM within someone-chip computers, such as 8031 , 8032, 80C ,etc.. (4)Four 8 run side by side I/O interface P0 four P3, each mouth can use as introduction, may use as exporting too. (5)Two timer / counter, each timer / counter may set up and count in the way, used to count to the external incident, can set up into a timing way too, and can according to count or result of timing realize the control of the computer. (6)Five cut off cutting off the control system of the source .(7)One all duplexing serial I/O mouth of UART (universal asynchronous receiver/transmitter (UART)), is it realize one-chip computer or one-chip computer and serial communication of computer to use for. (8)Stretch oscillator and clock produce circuit, quartz crystal finely tune electric capacity need outer. Allow oscillation frequency as 12 megahits now at most. Every the above-mentioned part was joined through the inside data bus .Among them, CPU is a core of the one-chip computer, it is the control of the computer and command center, made up of such parts as arithmetic unit and controller , etc.. The arithmetic unit can carry on 8 persons of arithmetic operation and unit ALU of logic operation while including one, the 1 storing device temporaries of 8, storing device 2 temporarily, 8's accumulation device ACC, register B and procedure state register PSW, etc. Person who accumulate ACC count by 2 input ends entered of checking etc. temporarily as one operation often, come from person who store 1 operation is it is it make operation to go on to count temporarily , operation result and loopback ACC with another one. In addition, ACC is often regarded as the transfer station of data transmission on 8051 inside. The same as general microprocessor, it is the busiest register. Help remembering that agreeing with A expresses in the order. The controller includes the procedure counter, the order is deposited, the order deciphers the oscillator and timing circuit, etc. The procedure counter is made up of counter of 8 for two, amounts to 16. It is a byte address counter of the procedure in fact, the content is the next IA that will carried out in PC. The content which changes it can change the direction that the procedure carries out. Shake the circuit in 8051 one-chip computers, only need outer quartz crystal and frequency to finely tune the electric capacity, its frequency range is its 12MHZ of 1.2MHZ. This pulse signal, as 8051 basic beats of working, namely the minimum unit of time. 8051 is the same as other computers, the work in harmony under the control of the basic beat, just like an orchestra according to the beat play that is commanded.There are ROM (procedure memory, can only read)and RAM in 8051 slices (data memory, can is it can write)two to read, they have each independent memory address space, dispose way to be the same with general memory of computer. Procedure 8051 memory and 8751 slice procedure memory capacity 4KB, addressbegin from 0000H, used for preserving the procedure and form constant. Data 8051- 8751 8031 of memory data memory 128B, address false 00FH, use for middle result to deposit operation, the data are stored temporarily and the data are buffered etc.. In RAM of this 128B, there is unit of 32 bytes that can be appointed as the job register, this and general microprocessor is different, 8051 slice RAM and job register rank one formation the same to arrange the location. It is not very the same that the memory of MCS-51 series one-chip computer and general computer disposes the way in addition. General computer for first address space, ROM and RAM can arrange in different space within the range of this address at will, namely the addresses of ROM and RAM, with distributing different address space in a formation. While visiting the memory, corresponding and only an address Memory unit, can ROM, it can be RAM too, and by visiting the order similarly. This kind of memory structure is called the structure of Princeton. 8051 memories are divided into procedure memory space and data memory space on the physics structure, there are four memory spaces in all: The procedure stores in one and data memory space outside data memory and one in procedure memory space and one outside one, the structure forms of this kind of procedure device and data memory separated form data memory, called Harvard structure. But use the angle from users, 8051 memory address space is divided into three kinds: (1) in the slice, arranges blocks of FFFFH, 0000H of location, in unison outside the slice (use 16 addresses). (2) The data memory address space outside one of 64KB, the address is arranged from 0000H 64KB FFFFH (with 16 addresses) too to the location. (3) Data memory address space of 256B (use 8 addresses). Three above-mentioned memory space addresses overlap, for distinguishing and designing the order symbol of different data transmission in the instruction system of 8051: CPU visit slice, ROM order spend MOVC , visit block RAM order uses MOVX outside the slice, RAM order uses MOV to visit in slice.8051 one-chip computer have four 8 walk abreast I/O port, call P0, P1, P2 and P3. Each port is 8 accurate two-way mouths, accounts for 32 pins altogether. Every one I/O line can be used as introduction and exported independently. Each port includes a latch (namely special function register), one exports the driver and aintroduction buffer. Make data can latch when outputting, data can buffer when making introduction, but four function of pass way these self-same. Expand among the system of memory outside having slice, four ports these may serve as accurate two-way mouth of I/O in common use. Expand among the system of memory outside having slice, P2 mouth see high 8 address off; P0 mouth is a two-way bus, send the introduction of 8 low addresses and data/export in timesharingThe circuit of 8051 one-chip computers and four I/O ports is very ingenious in design. Familiar with I/O port logical circuit, not only help to use ports correctly and rationally, and will inspire to designing the peripheral logical circuit of one-chip computer to some extent. Load ability and interface of port have certain requirement, because output grade, P0 of mouth and P1 end output, P3 of mouth grade different at structure, so, the load ability and interface of its door demand to have nothing in common with each other. P0 mouth is different from other mouths; its output grade draws the resistance supremely. When using it as the mouth in common use to use, output grade is it leak circuit to turn on, is it is it urge NMOS draw the resistance on taking to be outer with it while inputting to go out to fail. When being used as introduction, should write "1" to a latch first. Everyone with P0 mouth can drive 8 Model LS TTL load to export. P1 mouth is an accurate two-way mouth too, used as I/O in common use. Different from P0 mouth output of circuit its, draw load resistance link with power on inside have. In fact, the resistance is that two effects are in charge of FET and together: One FET is in charge of load, its resistance is regular. Another one can is it lead to work with close at two states, make its President resistance value change approximate 0 or group value heavy two situation very. When it is 0 that the resistance is approximate, can draw the pin to the high level fast ; When resistance value is very large, P1 mouth, in order to hinder the introduction state high. Output as P1 mouth high electricity at ordinary times, can is it draw electric current load to offer outwards, draw the resistance on needn't answer and thinning. Here when the port is used as introduction, must write into 1 to the corresponding latch first too, and make FET end. Relatively about 20,000 ohms because of the load resistance in scene and because 40,000 ohms, will not exert an influence on the data that are input.The structure of P2 some mouth is similar to P0 mouth, there are MUX switches. Is it similar to mouth partly to urge, but mouth large a conversion controls some than P1? P3 mouth one multi-functional port, mouth getting many than P1 it have “and”3 doors and 4 buffers". Two parts these, make her besides accurate two-way function with P1 mouth just, can also use the second function of every pin, “and”door 3 functions one switch in fact, it determines to be to output data of latch to output second signal of function. Act as W =at 1 o'clock, output Q end signal; Act as Q =at 1 o'clock, can output W line signal. At the time of programming, it is that the first function is still the second function but needn't have software that set up P3 mouth in advance. It hardware not inside is the automatic to have two function outputted when CPU carries on SFR and seeks the location (the location or the byte ) to visit to P3 mouth /at not lasting lining, there are inside hardware latch Qs =1.The operation principle of P3 mouth is similar to P1 mouth.Output grade, P3 of mouth, P1 of P1, connect with inside have load resistance of drawing, every one of they can drive 4 Model LS TTL load to output. As while inputting the mouth, any TTL or NMOS circuit can drive P1 of 8051 one-chip computers as P3 mouth in a normal way. Because draw resistance on output grade of them have, can open a way collector too or drain-source resistance is it urge to open a way, do not need to have the resistance of drawing outerly. Mouths are all accurate two-way mouths too. When the conduct is input, must write the corresponding port latch with 1 first . As to 80C51 one-chip computer, port can only offer milliamp ere of output electric currents, is it output mouth go when urging one ordinary basing of transistor to regard as, should contact a resistance among the port and transistor base , in order to the electricity while restraining the high level from exporting P1~P3 Being restored to the throne is the operation of initializing of an one-chip computer. Its main function is to turn PC into 0000H initially, make the one-chip computer begin to hold the conduct procedure from unit 0000H. Except that the ones that enter the system are initialized normally, as because procedure operate it make mistakes or operate there aren't mistake, in order to extricate oneself from a predicament , need to be pressed and restored to the throne the key restarting too. It is an input end which is restored to。

外文文献翻译原文+译文

外文文献翻译原文+译文

外文文献翻译原文Analysis of Con tin uous Prestressed Concrete BeamsChris BurgoyneMarch 26, 20051、IntroductionThis conference is devoted to the development of structural analysis rather than the strength of materials, but the effective use of prestressed concrete relies on an appropriate combination of structural analysis techniques with knowledge of the material behaviour. Design of prestressed concrete structures is usually left to specialists; the unwary will either make mistakes or spend inordinate time trying to extract a solution from the various equations.There are a number of fundamental differences between the behaviour of prestressed concrete and that of other materials. Structures are not unstressed when unloaded; the design space of feasible solutions is totally bounded;in hyperstatic structures, various states of self-stress can be induced by altering the cable profile, and all of these factors get influenced by creep and thermal effects. How were these problems recognised and how have they been tackled?Ever since the development of reinforced concrete by Hennebique at the end of the 19th century (Cusack 1984), it was recognised that steel and concrete could be more effectively combined if the steel was pretensioned, putting the concrete into compression. Cracking could be reduced, if not prevented altogether, which would increase stiffness and improve durability. Early attempts all failed because the initial prestress soon vanished, leaving the structure to be- have as though it was reinforced; good descriptions of these attempts are given by Leonhardt (1964) and Abeles (1964).It was Freyssineti’s observations of the sagging of the shallow arches on three bridges that he had just completed in 1927 over the River Allier near Vichy which led directly to prestressed concrete (Freyssinet 1956). Only the bridge at Boutiron survived WWII (Fig 1). Hitherto, it had been assumed that concrete had a Young’s modulus which remained fixed, but he recognised that the de- ferred strains due to creep explained why the prestress had been lost in the early trials. Freyssinet (Fig. 2) also correctly reasoned that high tensile steel had to be used, so that some prestress would remain after the creep had occurred, and alsothat high quality concrete should be used, since this minimised the total amount of creep. The history of Freyssineti’s early prestressed concrete work is written elsewhereFigure1:Boutiron Bridge,Vic h yFigure 2: Eugen FreyssinetAt about the same time work was underway on creep at the BRE laboratory in England ((Glanville 1930) and (1933)). It is debatable which man should be given credit for the discovery of creep but Freyssinet clearly gets the credit for successfully using the knowledge to prestress concrete.There are still problems associated with understanding how prestressed concrete works, partly because there is more than one way of thinking about it. These different philosophies are to some extent contradictory, and certainly confusing to the young engineer. It is also reflected, to a certain extent, in the various codes of practice.Permissible stress design philosophy sees prestressed concrete as a way of avoiding cracking by eliminating tensile stresses; the objective is for sufficient compression to remain after creep losses. Untensionedreinforcement, which attracts prestress due to creep, is anathema. This philosophy derives directly from Freyssinet’s logic and is primarily a working stress concept.Ultimate strength philosophy sees prestressing as a way of utilising high tensile steel as reinforcement. High strength steels have high elastic strain capacity, which could not be utilised when used as reinforcement; if the steel is pretensioned, much of that strain capacity is taken out before bonding the steel to the concrete. Structures designed this way are normally designed to be in compression everywhere under permanent loads, but allowed to crack under high live load. The idea derives directly from the work of Dischinger (1936) and his work on the bridge at Aue in 1939 (Schonberg and Fichter 1939), as well as that of Finsterwalder (1939). It is primarily an ultimate load concept. The idea of partial prestressing derives from these ideas.The Load-Balancing philosophy, introduced by T.Y. Lin, uses prestressing to counter the effect of the permanent loads (Lin 1963). The sag of the cables causes an upward force on the beam, which counteracts the load on the beam. Clearly, only one load can be balanced, but if this is taken as the total dead weight, then under that load the beam will perceive only the net axial prestress and will have no tendency to creep up or down.These three philosophies all have their champions, and heated debates take place between them as to which is the most fundamental.2、Section designFrom the outset it was recognised that prestressed concrete has to be checked at both the working load and the ultimate load. For steel structures, and those made from reinforced concrete, there is a fairly direct relationship between the load capacity under an allowable stress design, and that at the ultimate load under an ultimate strength design. Older codes were based on permissible stresses at the working load; new codes use moment capacities at the ultimate load. Different load factors are used in the two codes, but a structure which passes one code is likely to be acceptable under the other.For prestressed concrete, those ideas do not hold, since the structure is highly stressed, even when unloaded. A small increase of load can cause some stress limits to be breached, while a large increase in load might be needed to cross other limits. The designer has considerable freedom to vary both the working load and ultimate load capacities independently; both need to be checked.A designer normally has to check the tensile and compressive stresses, in both the top and bottom fibre of the section, for every load case. The critical sections are normally, but not always, the mid-span and the sections over piers but other sections may become critical ,when the cable profile has to be determined.The stresses at any position are made up of three components, one of which normally has a different sign from the other two; consistency of sign convention is essential.If P is the prestressing force and e its eccentricity, A and Z are the area of the cross-section and its elastic section modulus, while M is the applied moment, then where ft and fc are the permissible stresses in tension and compression.c e t f ZM Z P A P f ≤-+≤Thus, for any combination of P and M , the designer already has four in- equalities to deal with.The prestressing force differs over time, due to creep losses, and a designer isusually faced with at least three combinations of prestressing force and moment;• the applied moment at the time the prestress is first applied, before creep losses occur,• the maximum applied moment after creep losses, and• the minimum applied moment after creep losses.Figure 4: Gustave MagnelOther combinations may be needed in more complex cases. There are at least twelve inequalities that have to be satisfied at any cross-section, but since an I-section can be defined by six variables, and two are needed to define the prestress, the problem is over-specified and it is not immediately obvious which conditions are superfluous. In the hands of inexperienced engineers, the design process can be very long-winded. However, it is possible to separate out the design of the cross-section from the design of the prestress. By considering pairs of stress limits on the same fibre, but for different load cases, the effects of the prestress can be eliminated, leaving expressions of the form:rangestress e Perm issibl Range Mom entZ These inequalities, which can be evaluated exhaustively with little difficulty, allow the minimum size of the cross-section to be determined.Once a suitable cross-section has been found, the prestress can be designed using a construction due to Magnel (Fig.4). The stress limits can all be rearranged into the form:()M fZ PA Z e ++-≤1 By plotting these on a diagram of eccentricity versus the reciprocal of the prestressing force, a series of bound lines will be formed. Provided the inequalities (2) are satisfied, these bound lines will always leave a zone showing all feasible combinations of P and e. The most economical design, using the minimum prestress, usually lies on the right hand side of the diagram, where the design is limited by the permissible tensile stresses.Plotting the eccentricity on the vertical axis allows direct comparison with the crosssection, as shown in Fig. 5. Inequalities (3) make no reference to the physical dimensions of the structure, but these practical cover limits can be shown as wellA good designer knows how changes to the design and the loadings alter the Magnel diagram. Changing both the maximum andminimum bending moments, but keeping the range the same, raises and lowers the feasible region. If the moments become more sagging the feasible region gets lower in the beam.In general, as spans increase, the dead load moments increase in proportion to the live load. A stage will be reached where the economic point (A on Fig.5) moves outside the physical limits of the beam; Guyon (1951a) denoted the limiting condition as the critical span. Shorter spans will be governed by tensile stresses in the two extreme fibres, while longer spans will be governed by the limiting eccentricity and tensile stresses in the bottom fibre. However, it does not take a large increase in moment ,at which point compressive stresses will govern in the bottom fibre under maximum moment.Only when much longer spans are required, and the feasible region moves as far down as possible, does the structure become governed by compressive stresses in both fibres.3、Continuous beamsThe design of statically determinate beams is relatively straightforward; the engineer can work on the basis of the design of individual cross-sections, as outlined above. A number of complications arise when the structure is indeterminate which means that the designer has to consider, not only a critical section,but also the behaviour of the beam as a whole. These are due to the interaction of a number of factors, such as Creep, Temperature effects and Construction Sequence effects. It is the development of these ideas whichforms the core of this paper. The problems of continuity were addressed at a conference in London (Andrew and Witt 1951). The basic principles, and nomenclature, were already in use, but to modern eyes concentration on hand analysis techniques was unusual, and one of the principle concerns seems to have been the difficulty of estimating losses of prestressing force.3.1 Secondary MomentsA prestressing cable in a beam causes the structure to deflect. Unlike the statically determinate beam, where this motion is unrestrained, the movement causes a redistribution of the support reactions which in turn induces additional moments. These are often termed Secondary Moments, but they are not always small, or Parasitic Moments, but they are not always bad.Freyssinet’s bridge across the Marne at Luzancy, started in 1941 but not completed until 1946, is often thought of as a simply supported beam, but it was actually built as a two-hinged arch (Harris 1986), with support reactions adjusted by means of flat jacks and wedges which were later grouted-in (Fig.6). The same principles were applied in the later and larger beams built over the same river.Magnel built the first indeterminate beam bridge at Sclayn, in Belgium (Fig.7) in 1946. The cables are virtually straight, but he adjusted the deck profile so that the cables were close to the soffit near mid-span. Even with straight cables the sagging secondary momentsare large; about 50% of the hogging moment at the central support caused by dead and live load.The secondary moments cannot be found until the profile is known but the cablecannot be designed until the secondary moments are known. Guyon (1951b) introduced the concept of the concordant profile, which is a profile that causes no secondary moments; es and ep thus coincide. Any line of thrust is itself a concordant profile.The designer is then faced with a slightly simpler problem; a cable profile has to be chosen which not only satisfies the eccentricity limits (3) but is also concordant. That in itself is not a trivial operation, but is helped by the fact that the bending moment diagram that results from any load applied to a beam will itself be a concordant profile for a cable of constant force. Such loads are termed notional loads to distinguish them from the real loads on the structure. Superposition can be used to progressively build up a set of notional loads whose bending moment diagram gives the desired concordant profile.3.2 Temperature effectsTemperature variations apply to all structures but the effect on prestressed concrete beams can be more pronounced than in other structures. The temperature profile through the depth of a beam (Emerson 1973) can be split into three components for the purposes of calculation (Hambly 1991). The first causes a longitudinal expansion, which is normally released by the articulation of the structure; the second causes curvature which leads to deflection in all beams and reactant moments in continuous beams, while the third causes a set of self-equilibrating set of stresses across the cross-section.The reactant moments can be calculated and allowed-for, but it is the self- equilibrating stresses that cause the main problems for prestressed concrete beams. These beams normally have high thermal mass which means that daily temperature variations do not penetrate to the core of the structure. The result is a very non-uniform temperature distribution across the depth which in turn leads to significant self-equilibrating stresses. If the core of the structure is warm, while the surface is cool, such as at night, then quite large tensile stresses can be developed on the top and bottom surfaces. However, they only penetrate a very short distance into the concrete and the potential crack width is very small. It can be very expensive to overcome the tensile stress by changing the section or the prestress。

专业外文文献翻译

专业外文文献翻译

附录1:英文原文The Renminbi's Dollar Peg at The Crossroads In the face of huge balance of payments surpluses and internal inflationary pressures,China has been in a classic conflict between internal and external balance under its dollar currency—basket peg. Over the longer term,China's large, modernizing,and diverse economy will need exchange rate flexibility and,eventually,convertibility with open capital markets。

A feasible and attractive exit strategy from the essentially fixed RMB exchange rate would be a two—stage approach,consistent with the steps already taken since July 2005,but going beyond them。

First,establish a limited trading band for the RMB relative to a basket of major trading partner currencies。

Set the band so that it allows some initial revaluation of the RMB against the dollar,manage the basket rate within the band if necessary,and widen the band over time as domestic foreign exchange markets develop. Second, put on hold ad hoc measures of financial account liberalization。

外文文献翻译(中英文)

外文文献翻译(中英文)

外文文献翻译(中英文)专业外语与文献阅读英文原文:NOVEL METHOD OF REALIZING THE OPTIMAL TRANSMISSION OF THE CRANK-AND-ROCKER MECHANISM DESIGN Abstract: A novel method of realizing the optimal transmission of the crank-and-rocker mechanism is presented. The optimal combination design is made by finding the related optimal transmission parameters. The diagram of the optimal transmission is drawn. In the diagram, the relation among minimum transmission angle, the coefficient of travel speed variation, the oscillating angle of the rocker and the length of the bars is shown, concisely, conveniently and directly. The method possesses the main characteristic. That it is to achieve the optimal transmission parameters under the transmission angle by directly choosing in the diagram, according to the given requirements. The characteristics of the mechanical transmission can be improved to gain the optimal transmission effect by the method. Especially, the method is simple and convenient in practical use.Keywords:Crank-and-rocker mechanism, Optimal transmission angle, Coefficient of travel speed variation INTRODUCTIONBy conventional method of the crank-and-rocker design, it is very difficult to realize the optimal combination between the various parameters for optimal transmission. The figure-table design method introduced in this paper can help achieve this goal. With given conditions, we can, by only consulting the designing figures and tables, get the relations between every parameter and another of the designed crank-and-rockermechanism. Thus the optimal transmission can be realized.The concerned designing theory and method, as well as the real cases of its application will be introduced later respectively.1ESTABLISHMENT OF DIAGRAM FOR OPTIMAL TRANSMISSION DESIGNIt is always one of the most important indexes that designers pursue to improve the efficiency and property of the transmission. The crank-and-rocker mechanism is widely used in the mechanical transmission. How to improve work ability and reduce unnecessary power losses is directly related to the coefficient of travel speed variation, the oscillating angle of the rocker and the ratio of the crank and rocker. The reasonable combination of these parameters takes an important effect on the efficiency and property of the mechanism, which mainly indicates in the evaluation of the minimum transmission angle.The aim realizing the optimal transmission of the mechanism is how to find themaximum of the minimum transmission angle. The design parameters are reasonably combined by the method of lessening constraints gradually and optimizing separately. Consequently, the complete constraint field realizing the optimal transmission is established.The following steps are taken in the usual design method. Firstly, the initial values of the length of rocker 3l and the oscillating angle of rocker ? are given. Then the value of the coefficient of travel speed variation K is chosen in the permitted range. Meanwhile, the coordinate of the fixed hinge of crank A possibly realized is calculated corresponding to value K .1.1 Length of bars of crank and rocker mechanismAs shown in Fig.1, left arc G C 2 is the permitted field of pointA . Thecoordinates of point A are chosen by small step from point 2C to point G .The coordinates of point A are02h y y c A -= (1)22A A y R x -= (2) where 0h , the step, is increased by small increment within range(0,H ). If the smaller the chosen step is, the higher the computational precision will be. R is the radius of the design circle. d is the distance from 2C to G .2c o s )2c o s (22c o s 33?θ--+=l R l d (3) Calculating the length of arc 1AC and 2AC , the length of the bars of themechanism corresponding to point A is obtained [1,2].1.2 Minimum transmission angle min γMinimum transmission angle min γ(see Fig.2) is determined by the equations [3]322142322m i n 2)(c o s l l l l l l --+=γ (4) 322142322m a x 2)(c o s l l l l l l +-+=γ (5) m a x mi n 180γγ-?=' (6) where 1l ——Length of crank(mm)2l ——Length of connecting bar(mm)3l ——Length of rocker(mm)4l ——Length of machine frame(mm)Firstly, we choose minimum comparing min γ with minγ'. And then we record all values of min γ greater than orequal to ?40 and choose the maximum of them.Secondly, we find the maximum of min γ corresponding to any oscillating angle ? which is chosen by small step in the permitted range (maximum of min γ is diffe rent oscillating angle ? and the coefficient of travel speed variation K ).Finally, we change the length of rockerl by small step similarly. Thus we3γcorresponding to the different length of bars, may obtain the maximum ofmindifferent oscillating angle ?and the coefficient of travel speed variation K.Fig.3 is accomplished from Table for the purpose of diagram design.It is worth pointing out that whatever the length of rocker 3l is evaluated, the location that the maximum o f min γ arises is only related to the ratio of the length of rocker and the length of machine frame 3l /4l , while independent of 3l .2 DESIGN METHOD2.1 Realizing the optimal transmission design given the coefficient of travelspeed variation and the maximum oscillating angle of the rockerThe design procedure is as follows.(1) According to given K and ?, taken account to the formula the extreme included angle θ is found. The corresponding ratio of the length of bars 3l /4l is obtained consulting Fig.3.+-=18011K K θ (7) (2) Choose the length of rocker 3l according to the work requirement, the length of the machine frame is obtained from the ratio 3l /4l .(3) Choose the centre of fixed hinge D as the vertex arbitrarily, and plot an isosceles triangle, the side of which is equal to the length of rocker 3l (see Fig.4), and=∠21DC C . Then plot 212C C M C ⊥, draw N C 1, and make angleθ-?=∠9012N C C . Thus the point of intersection of M C 2 and N C 1 is gained. Finally, draw the circumcircle of triangle 21C PC ?.(4) Plot an arc with point D as the centre of the circle, 4l as the radius. The arc intersections arc G C 2 at point A . Point A is just the centre of the fixed hinge of the crank.Therefore, from the length of the crank2/)(211AC AC l -= (8)and the length of the connecting bar112l AC l -= (9)we will obtain the crank and rocker mechanism consisted of 1l , 2l , 3l , and 4l .Thus the optimal transmission property is realized under given conditions.2.2 Realizing the optimal transmission design given the length of the rocker (or the length of the machine frame) and the coefficient of travel speed variationWe take the following steps.(1) The appropriate ratio of the bars 3l /4l can be chosen according to given K . Furthermore, we find the length of machine frame 4l (the length of rocker 3l ).(2) The corresponding oscillating angle of the rocker can be obtained consulting Fig.3. And we calculate the extreme included angle θ.Then repeat (3) and (4) in section 2.13 DESIGN EXAMPLEThe known conditions are that the coefficient of travel speed variation1818.1=K and maximum oscillating angle ?=40?. The crankandrockermechanism realizing the optimal transmission is designed by the diagram solution method presented above.First, with Eq.(7), we can calculate the extreme included angle ?=15θ. Then, we find 93.0/43=l l consulting Fig.3 according to the values of θ and ?.If evaluate 503=l mm, then we will obtain 76.5393.0/504==l mm. Next, draw sketch(omitted).As result, the length of bars is 161=l mm,462=l mm,503=l mm,76.534=l mm.The minimum transmission angle is=--+=3698.462)(arccos 322142322min l l l l l l γ The results obtained by computer are 2227.161=l mm, 5093.442=l mm, 0000.503=l mm, 8986.534=l mm.Provided that the figure design is carried under the condition of the Auto CAD circumstances, very precise design results can be achieved.4 CONCLUSIONSA novel approach of diagram solution can realize the optimal transmission of the crank-and-rocker mechanism. The method is simple and convenient in the practical use. In conventionaldesign of mechanism, taking 0.1 mm as the value of effective the precision of the component sizes will be enough.译文:认识曲柄摇臂机构设计的最优传动方法摘要:一种曲柄摇臂机构设计的最优传动的方法被提出。

5000字英文范文翻译类

5000字英文范文翻译类

In new network on 2 September Xinhua comprehensive report, the situation in Syria is currently in the United States of America in the teeth of the storm, President Obama issued a statement in August 31st, decided to take military action against the Syrian government target, the White House has formally asked Congress to authorize. But in the United States, Obama faces two trials of Congress and the public; in foreign countries, the multinational NATO would not send troops, many countries also oppose the United States plans. Analysis refers to the Syrian military command, Obama was "imminent", but his support for the difficulties, may "itself".The contradiction: the Congress attitude unknown Obama fears "riding a tiger"Local time on August 31st, the United States President Barack Obama issued a statement at the White House, said that "after careful consideration, I have decided that the United States should the regime in Syria to take military action against the target. It will not be indefinite intervention, we will not send ground troops, instead we aim to limit the action time and scale."But Obama said, he also made second decisions, is "to get authorization from Congress to", only the consent of Congress, I ordered the U.S. war on Syria. On the same day, the official White House to Congress a proposal, according to the United States Congress "War Powers Act" and the United Nations Security Council in 2004 passed a resolution, authorized the president to take military action in Syria.In the proposal, Obama asked Congress to use the authorization bill Syria, intended to deter, prevent and reduce blow, Syria continue to use chemical weapons and other weapons of mass destruction in the future. He also said, Syria internal conflict was resolved by political consultation.The analysis thinks, Obama remarks on the question of Syria to slam the brakes, to seek congressional approval for a military attack against Syria, is likely to lead to the United States at least 10 days delay action.However, Obama this "gambling" type decision will make it a tough fight. Obama broke the decades of practice, has announced that it will seek congressional approval Syria suspected use chemical weapons to act. But the United States senators would support Obama, will defeat him swallow bitter is still uncertain.Analysis pointed out that, Obama this bet is risky, he bet he could get Congress agreed to a limited attack Syria, defending against the international ban, the United States national security interests, and to protect Turkey, Jordan, Israel and other allies in the middle east.Obama had previously insisted, he retained ignore Congress decided to attack the right, White House officials said the change would give Obama more time to win internationalsupport. But for Obama, the most difficult and most threatening the authority of the president's war, or between members of Congress of political wrangling, because it cannot determine the Congress will support the attack on Syria.Observers caution, Obama could face the same fate with British Prime Minister Cameron. Cameron for the British Parliament authorized military action, but was rejected.Obama may be full of confidence, that he can win the vote in the Democratic controlled senate. The Senate also has many Republicans to take military action. However, he is in the house of Representatives won the support of the opportunity is not sure. The house has many conservative core people everywhere, to interfere with Obama's plan.In addition, the American people on the government military intervention plan highlights the ambivalence, and the Obama administration, Congress and the U.S. is unease shrouded. The Afghan war and the Iraq war, costly delay for a long time, the American people are unwilling to once again involved in the conflict in the middle east.The United States National Broadcasting Company (NBC) recently in a poll, half of Americans polled for the government of Syria military strikes do not support, only 35% behind Obama in the process encountered a time he was the most difficult questions of the 700 respondents.Only 1/5 of respondents said the military action, which is in the American national interest, and only 27% of the people think that the military can make the situation in Syria.If the United States to take action, 56% of people said that, the aim should be to prevent the use of chemical weapons. Only a small number of people (16% or less), military action to overthrow the Assad regime or stop Syria clashes between government forces and armed opposition.Outside the opposition: 12 NATO countries to the international community to anti war emotionWhen Obama published "on the Syrian military" statement on the same day, the United States anti war organizations held a protest outside the White House, shouting anti war slogans. People playing white banners and placards reading "not yellow, the Syrian war", "the Syrian military built on lies" etc.. The activities of the organization responsible person said, the day before and after the estimated 500 people have been involved in the protests, the organizers also prepared during the three day "Labor Day" long weekend continue to hold protest in front of the White House, where all over the United States would have to Washington to participate in.In August 31st, the British capital London is also the outbreak of large-scaledemonstrations, oppose aggression against Syria. According to the organization of this parade "anti war alliance", a total of 5000 people took part in the parade.The British Parliament in August 29th voted against Prime Minister Cameron to attack Syria's proposal, was named the greatest shame Cameron to be in power for three years "suffer". Although Obama assured Cameron that the relationship between them is still strong, but the British media will Cameron's the signs of failure as the so-called "special relationship" and "doomsday". They worry, support for military action.。

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附录外文文献原文1.IntroductionMarketing continues to be a mystery to those who create it and to those who sponsor it. Often, the ad that generates record-breaking volume for a retail store one month is repeated the following month and bombs. A campaign designed by the best Madison Avenue ad agency may elicit mediocre response. The same item sells like hotcakes after a 30-word classified ad, with abominable grammar, appears on page 35 of an all-advertising shopper tossed on the front stoops of homes during a rainstorm! The mystery eludes solution but demands attention. The success of an enterprise and development of enterprises depends to a large extent on whether or not they have advanced, meet the needs of the enterprise marketing strategy. For Marketing is the definition, The well-known American scholar Philips marketing of the core marketing concept of the following description : "Marketing is individuals or groups to create, provide and exchange with other valuable products, to satisfy their own needs and desires of a social activities and management process. " In the core concept contains a number of elements: needs, desires and needs; Products or provide; Value and satisfaction; exchange and transactions; and networking; market; Marketing and sales were a series of concept.This article is devoted to the idea that your marketing results can be improved through a better Understanding of your customers. This approach usually is referred to as the marketing concept.Putting the customer first is probably the most popular phrase used by firms ranging from giant conglomerates to the corner barber shop, but the slogan zing is often just lip service. The business continues to operate under the classic approach --"Come buy this great product if you dedicate your activities exclusively to solving your customer's problems. The quality of services, and enterprises to cultivate customers satisfaction and loyalty, and can create enterprise value.Any marketing program has a better chance of being productive if it is timed, designed and written to solve a problem for potential customers and is carried out in a way that the customer understands and trusts. The pages that follow will present the marketing concept of putting the customer first. Marketing is a very complex subject; it deals with all the steps between determining customer needs and supplying them at a profit. In addition to some introductory material on marketing, this publication includes practical material on the marketing approaches to budgeting, layout design, and headline writing, copywriting and media analysis. So that a clear understanding of enterprise marketing strategy to improve the operations of enterprises.2.The marketing conceptMarket positioning is identifying the target market, enterprises will adopt what marketing methods, which provide products and services the target market and competitors to show distinction, thereby establishing corporate image and obtain favorable competitive position. Market positioning is a process of enterprise differentiation process, how to find the differences, identify differences and show differences. Today too many similar products, consumers how to choose Consumers buy what is the justification.On the effective positioning for a solution.Positioning is the first to propose in the advertising industry, advertising emphasized in the eyes of the public who left the location, And people often prefer preconceptions; If enterprises can target your customers mind to establish a definite position, to the consumer a reason to buy, enterprises can often compete in an advantageous position.Marketing is an economy built on science, behavioral science and modern management theory on the basis of applied sciences. It enterprise marketing activities and to study law,with full, comprehensive, practical features. As a modern enterprise "businesses" Marketing system introduced in the market economy under the conditions of the enterprises should have a sense of the market, business sense, Marketing strategies and methods. With China's economy growing prosperity, the market competition is becoming increasingly fierce; enterprises need Modern Marketing Theory as the guide. In the initial stage, a number of enterprises have marketing only as a help to product sales growth strategy and means If so far, many Chinese enterprises remain with the Department of Marketing with sales of two and one; When people realize that to meet the needs of the customer-oriented marketing concept should become an enterprise operating philosophy, and the enterprise's overall business activities have an impact, there will be a marketing position inappropriately increase the tendency For many people believe that marketing should be the decision-making levels of guiding ideology, rather than the level of implementation work. Marketing of the enterprise understanding of the position is not correct, will be marketing in the enterprise application will be affected. Marketing work is to open up markets, capture the market and expand the market work, enterprise development, and production activities should open up the market for services, a market that is the basis of the final services in the market. Marketing work is based on enterprise customers as the starting point for the reproduction process, and ensures the customer as the focus of the process of reproduction.That customer demand-oriented, according to the actual needs of customers developing marketable products, and targeted marketing of the market, and its sales to meet the needs of customers. With enterprises to become the main players in themarket, corporate marketing work more salient position, business leaders must attach great importance to it.Unfortunately, there is still a misunderstanding about the word marketing. Many people, including top executives, use it as a sophisticated term for selling. Marketing representative is commonly used in ads to recruit salespeople. Actually, marketing is a way of managing a business so that each critical business decision is made with full knowledge of the impact it will have on the customer.Here are some specific ways in which the marketing approach differs from the classic, or sales, approach to managing a business.①In the classic approach, engineers who develop the product and finally to engineers who produce it. Thus, the sales approach only ends with the customer, while the marketing approach begins and ends with the customer.②The second major difference between the sales and marketing approaches is the focus of management. The sales approach almost always focuses on volume while the marketing approach focuses on profit. In short, under the classic (sales) approach the customer exists for the business, while under the marketing approach the business exists for the customer.The marketing concept is a management plan that views all marketing components as part of a total system that requires effective planning, organization, leadership and control. It is based on the importance of customers to a firm, and states。

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