HUNAN UNIVERSITY
英文文档翻译
（英文原文）
设计（论文）题目High Quality Web-Application
Development on Java EE Platform 学生姓名张刚
专业班级10级软件工程5班
指导老师李珩
系主任（院长）林亚平
评阅人
2014 年 4 月16 日
High Quality Web-Application Development on Java EE Platform Harshad B. Praj'apati Information Technology Department Dharmsinh Desai University Nadiad, India https://www.doczj.com/doc/7314347602.html, Vipul K. Dabhi Information Technology DepartmentDharmsinh Desai University Nadiad, India https://www.doczj.com/doc/7314347602.html, Abstract：Quality of web-applications plays major role in its success. And the high quality web-application is really possible by following high quality web engineering process. The use of strong web-application architecture with strong development platform not only make web-applications robust and of high quality but also give web-application an ability to meet changing and demanding customer requirements in efficient manner. A Model View Controller （MVC) design pattern has remained fundamental architectural design pattern even after great evolution in architectures of user interactive applications. In this paper, we discuss the support for achieving quality attributes for the web-application, the support for web-application development process and the support for meeting demanding features of web application on Java EE platform. This contribution will help a lot for small scale as well as large scale web-application development and for moulding web-application into a future's high quality finished product from inception phase itself.
Key-words:MVC;Web Application;Java EE;Quality Attributes;High Quality Web Development.
1、Introduction
Along with the great demand of web-applications in the era of pervasive and ubiquitous computing, a number of issues related to quality of web-applications [1] have also gained a great attention in web-application development process. Great competitions in the web-application business compel web-application developers more quality conscious. It will be of great value if a web-application could survive against demanding and changing customer requirements, and changing business requirements.
Building high quality web-application is really a difficult,and challenging task. But the support for right development process, methods, tools, and people really make possible to achieve high quality of web-application. As the development platform influences associated development process, methods, tools, and people, it really plays a major role for making development process simple, efficient, and robust and for achieving high quality of web-application.
Java EE platform [7] is open, standard based n[8] hardware and OS independent platform on which distributed enterprise applications can be developed and run. As the applications targeted on Java EE platform are vendor neutral, the organization does not face the problem of vendor lock-in. The Java EE platform based web-applications use Model/View/Controller (MVC) [2] design pattern [3] for three architectural components: presentation logic, controller logic,and entity/business logic. We discuss MVC design pattern used in traditional GUI based applications and also discuss how it is adapted in the architecture of Java EE platform based web-applications. We analyze the Java EE platform as per (i)quality attributes requirements[1] of web-applications (ii) related support in development process (iii) related support to involved people during development, and present our results in quick digestible form.Our results indicate that web-application development on Java EE platform has a great value in providing high quality to web-application, satisfying changing customer requirements and satisfying changing business requirements.
The presented work, in this paper, concentrates on achieving high quality for web-application developed on Java EE platform from different perspective of overall development process. The related work in the category is as follows. The Web-application development using the MVC design pattern can be found in [4]. The MVC design pattern in https://www.doczj.com/doc/7314347602.html, and JSP frameworks can be found in [5]. The quality characteristics and attributes for web sites can be found in [1].
The Section II discusses the MVC design pattern in traditional GUI application architecture and its adaptation in web-application architecture. The Section III presents web-application development process and available support for it on Java EE platform. The Section IV presents available valuable features for web-application on Java EE platform. Section V presents the result of Java EE platform analysis for achieving high quality of web-application and its components. And finally the Section VI presents the conclusions and direction for future research work.
2.The web-Application architecture on Java EE platform using MVC Design pattern
An MVC [2] design pattern [3] has remained fundamental architectural design pattern even after great evolution in the architectures of user interactive applications. So,we would like to provide short introduction on it to the readers before we discuss its usage in web-application architecture on Java EE platform [7].
A.The MVC design pattern
The MVC design pattern is widely used by programmer,software designer, and GUI component developer to architect the widget they are developing. The MVC design pattern, as shown in Figure 1, consists of three kinds of objects: Model, View, and Controller, which handle three basic responsibilities of any widget: entity(data), boundary (presentation), and control (behavior) respectively. The model encapsulates application data and business logic; the view handles rendering of application data and visual interface to user; and the controller handles user's interaction with the application.
The MVC design pattern separates views and models by establishing subscribe/notify protocol between them. A view object must ensure that its appearance reflects the state of the model. The model object is independent of both view and controller objects, so it is possible to have multiple views (presentations) of same model (data). All associated views can subscribe with model and model notifies them about its state change.
When user interacts with the MVC design pattern based GUI form or page, all fired events are captured by controller object. The controller then decides whether the fired event is related to change in state of model or change in state of view.As an example, when the user fires event related to changing value in text field, the controller calls the method of model to change its content. But if the user performs horizontal or vertical scroll-up or scroll-down, the model content does not change and only the view should be notified to reflect the changes in its appearance.
B.Web-Application Architecture in Java EE platform
In a stand-alone application, generally the model, view, and controller live on the same machine. But in a distributed web-application, the application architecture is different; however,the MVC design pattern is so general that it can still be applied to its architecture. The Java EE platform based web-applications utilize MVC based architecture as shown in Figure2.
In Java EE platform based web-application architectures, the servlet [10] component is used as a controller; the Java Bean component is used as a model; and te Java Server Pages [11](JSP) page is
used as a view template. The Enterprise Java Bean (EJB) [12]l can be used as a.model, which can be located environment unlike Java Bean.The JSP technology is used for creating view; and te JSP page is considered as a view template. The execution of this JSP page generates the view - HTML [13] content.
The Java EE platform provides many system services to web-application components. Java Bean platform provides support for security, authentication, authorization ,transaction. The database connection management is handled by the Java EE platform and it is configurable externally in deployment descriptor, so the model component does not need to worry about those details. Thus, the responsibility of model component is just to handle only business data and business logic. The authentication and authorization service is also provided by the Java EE platform to servlet and this service is also configurable externally in deployment descriptor. The container mediates between the servlet components and web browser for each HTTP [14] requests and applies the services as configured d in the development descriptor.
3.Web-Application Development process on Java EE platform
In this section, we discuss about web-application development process in Java BE platform [7] and the support available for web-application development from the Java EE platform.
A.Web-Application development process
A typical development process on Java EE platform involves following tasks: designing,
coding,creating deployment descriptor, packaging, assembling, and deployment. These tasks are also applicable to web-application development also. The Java EE platform specification [8]specifies the roles and their responsibilities in Java enterprise application development. We present here these roles and their,responsibilities in various phases of web-application development process.The Table I shows the major roles played by involved people during development, their role based responsibilities and their involvement in specific development phases.
B.Support In Development Process
The development becomes efficient if tools/technology support is available during coding, testing, integration,deployment and maintenance phases. Here, we discuss how Java EE platform provides support during all these phases to make development process efficient.
1). Support in Coding: The development environment should provide facilities of avoiding typos, require minimal effort for adding new functionalities, and provide support for standards based technology and tools. Very sophisticated development tools are available for software development on Java EE platform. The Netbeans IDE [15] and Eclipse IDE [16] are among them. These IDEs are equipped with sophisticated editors. Few of such features are auto code completion, re-factoring, code insertion, syntax highlighting to avoid typo errors, fixing package imports, getter/setter handling,and code insertion for calling of EJBs.These features help a lot while developing servlet, JSP, JavaBean and EJB components.
2).Support in Testing: Good debugging and unit testing support are basic requirement in testing process. The Java platform [9] comes with debugger jdb and the IDEs such as Netbeans and Eclipse provide good debugging support. The JUnit [17] provides regression testing framework for unit testing.It can accelerate programming and increase the quality of code. It provides API for easily creating Java test cases, comprehensive assertion facilities, test runners for running tests, aggregation facility and reporting. All these features help the developers from embedding several println( calls in actual code and manually preparing test results in structured fashion. Adding and then removing individual println( for testing purpose is very frustrating task;and it can not be replicated into similar classes easily.
3)Support in Integration and Deployment:The integration and deployment of web-application should be as easy as possible to minimize deployment time and downtime. And the deployment process should be independent of different hosting application server providers.Since Java technology[9] is standard based,the web-application developed using it will run on any Java EE compliance[8] application server without any modification in code.The web-application is free from vendor lock-in. The Java EE platform specifies vendor neutral configuration in standard deployment descriptor and vendor specific deployment descriptor files.The vendor specific configuration includes abstract security roles mapping with target security system, data source references, and other resource configuration.
4)Support in Maintenance: The Java EE platform specification clearly specifies the roles and responsibilities of different involved people. As discussed above. All these roles apply to web as well as enterprise module/application development. Three main roles: developer, assembler, and deployer simplify the whole development task. All three basic components: servlet, JSP and JavaBean/EJB components can be implemented and maintained independently by servlet developer, JSP developer, and Java/EJB developer,respectively.
4.Valuable Features For Web-Application On Java EE Platform
As Java technology [9] is object oriented and platform independent, many features such as scalability, portability, reusability, security, high performance, flexibility are inherent in Java classes or components. Both Servlet [10] and JavaBean components are java classes, so above stated features are inherent in them. This also applies to EJB [12] component also,which is collection of java classes and deployment descriptor.JSP [11] scripting language is used to create JSP page.Although a JSP page looks like an HTML[13] kind of page, at execution time it is a translated java class which gets executed. In short, all three components: servlet, JavaBean/EJB, and JSP that are used in implementing MVC [2] design pattern [3] on Java EE platform [7] are scalable, portable, reusable, secure, high performance, flexible. The following available features on the Java EE platform add value to web-application. And in certain business/customer requirements, they are indispensable. A.Security
The communication security (confidentiality and integrity) is provided through SSL [18] support.For SSL support, the application server providers. Since Java technology [9] is SSL connector should be configured on the Java EE container and the server certificate signed by Certifying Authority (CA)[18] should be installed on the Java EE container.A Java EE based web-application is configured for confidentiality and integrity declaratively. The Figure 3 shows three configurations related to security aspect of web-application. The part shown under is related to confidentiality and integrity of data that gets transmitted between Java EE container and web-browser.
The part under in Figure 3 declares that user authentication must be performed before granting access to resources. And it declares that authentication method is of type FORM.
The authorization part includes which operations on which resources are allowed by which users. The part inside
B.Transaction Processing
Java EE platform supports container-managed transaction and bean managed transaction for session bean and message driven bean (MDB) [12]. In Container-managed transaction,the enterprise bean transaction's boundaries using begin transaction and commit transaction. Instead, the transaction is configured in deployment descriptor. The container begins a transaction immediately before a
business method in enterprise starts. It commits the transaction just before the business method in enterprise bean exits. If an exception gets generated during business method execution, the container will automatically roll back the transaction. The support for only either a single transaction or no transaction at all is available from container managed transaction. For fine-grained control over transaction, the bean-managed transaction can be used. Here the code in the session or message driven bean explicitly marks the boundaries of the transaction using Java Transaction API(JTA).
c.Support For Session Management
Most of the web-applications on the Internet handle the session using cookie mechanism. So, the users, who are accessing such web-applications from browsers that do not support cookie mechanism, cannot participate in session and will not be able to access any personal resource. The encode URL mechanism on Java EE platform automatically determines whether the client's browser supports the cookie or not, and then decides how the information about session identification should be stored on client machine. If the client's browser does not support the cookie or the cookie feature has been disabled by the user, the session id value is encoded in URL part that client is going to use .
D.Customized error-pages
If a user is trying to access a resource, which is not available, the server shows the error message 404 (SC_NOT_FOUND) resource not found exception. Instead, the error page containing beautiful description in non-technical English language is shown, the user will really understand the cause of problem and sometimes feels that you care for the users. A good web-application should not show the error messages generated by application server or web-server directly to users. As an example, a web-application can be configured for 404 resource not found exception as shown in Figure 4. Using this configuration, the error pages for user-defined error messages can also be specified. Instead of error-code, the exception-type can also be specified. The resourceNotFound.html file would contain error message in a language understandable to user.
E.Internationalization/Multi-language Support
If information is provided to users in a language that they understand and use, it would be easier for users to understand and use the application. The Unicode support for strings is inherent in the Java language [9]. The language also supports locale specific formatting of number, currency, date, time, etc. All such supports help a lot in making the Java EE platform [7]based web-application an internationalized one and they also increase the usability of web-application across the world.
5.Achieving Quality For The Web-Application And Its Components On Java EE Platform
The quality of individual components also affect in achieving overall quality of whole application. We, first, present here important quality attributes of components and how these quality attributes are satisfied for all three components: Model, View, and Controller. The related analysis and results are presented in Table II.Second,the design of any web-application includes various design tasks [6]. These design tasks and available support for them on Java EE platform [7] are presented in Table III. Third, the overall support for quality attributes [1] to web-application as a whole determines the overall quality.These quality attributes, criteria involved in achieving these quality attributes and
available support for them on Java EE platform are presented in Table IV.
6.Conclusion
We analyzed the Java EE platform as per quality attributes requirements of web-applications and found that quality attributes: usability, functionality, reliability, efficiency and maintainability can all be satisfied with it. From the discussion it is evident that Java EE platform simplifies the designing,development, deployment, integration and testing process of web-application without compromising high quality. It also empowers the development of web-application with scalability,portability, interoperability, reusability, flexibility and security.
Many frameworks for web-application development are available on Java EE platform, but no one is found providing support for high quality distributed web-application. In future,we intend to work on developing distributed high quality web-application framework on Java EE platform.
7.References
[1] Olsina, L. et al., "Specifying quality characteristics and attributes for web sites," in Proc. 1st ICSE Workshop on Web Engineering, ACM, Los Angeles, May 1999.
[2] G. E. Krasner and S. T. Pope, "A Cookbook for Using the Model-View- Controller User-Interface Paradigm in Smalltalk-80," Journal of Object- Oriented Programming, August/September 1988. [3] E. Gamma, Design Pattems: Elements of Reusable Object-Oriented Software, Addison-Wesley, 1994.
[4] A. Leff and J. T. Rayfield "Web-application development using the view/controller design pattem," in Proceedings of the 5th IEEE International Conference on Enterprise Distributed Object Computing, 2001, pp. 118-127.
[5] F. A. Masoud, Dana. H. Halabi and Deema. H. Halabi, "https://www.doczj.com/doc/7314347602.html, and JSP frameworks in model view controller implementation," in Proceedings of Information and Communication Technologies, 2006.ICTTA'06, pp. 3593-3598.
[6] R. S. Pressman, Software Engineering: A Practitioner's Approach 6e, McGraw Hill, 2005.
[7] Sun MicroSystem. Java Enterprise Edition. http:// https://www.doczj.com/doc/7314347602.html,/javaee/
[8] Java Community Process. https://www.doczj.com/doc/7314347602.html,/
[9] Sun MicroSystem. Java Technology. https://www.doczj.com/doc/7314347602.html,.
[10] Sun MicroSystem. Java Servlet Technology Implementation and Specification.
[11] Sun MicroSystem. Java Server Pages. https://https://www.doczj.com/doc/7314347602.html,/products/jsp/
[12] Sun MicroSystem. Enterprise JavaBeans Specifications.
[13] W3C Specifications. https://www.doczj.com/doc/7314347602.html,
[14] RFC: http protocol, https://www.doczj.com/doc/7314347602.html,/Protocols/ifc2616/rfc2616.html
[15] RFC : SSL, www.ietforg/rfc/rfc2246.txt
Lesson One: The Time Message Elwood N, Chapman 新的学习任务开始之际，千头万绪，最重要的是安排好时间，做时间的主人。本文作者提出了7点具体建议，或许对你有所启迪。 1 Time is tricky. It is difficult to control and easy to waste. When you look a head, you think you have more time than you need. For Example,at the beginning of a semester, you may feel that you have plenty of time on your hands, but toward the end of the term you may suddenly find that time is running out. You don't have enough time to cover all your duties (duty), so you get worried. What is the answer? Control! 译：时间真是不好对付，既难以控制好，又很容易浪费掉，当你向前看时，你觉得你的时间用不完。例如，在一个学期的开始，你或许觉得你有许多时间，但到学期快要结束时，你会突然发现时间快用光了，你甚至找不出时间把所有你必须干的事情干完，这样你就紧张了。答案是什么呢？控制。 2 Time is dangerous. If you don't control it, it will control you. I f you don't make it work fo r you, it will work against you. So you must become the master of time, not its servant. As a first-year college student, time management will be your number one Problem. 译：时间是危险的，如果你控制不了时间，时间就会控制你，如果你不能让时间为你服务，它就会起反作用。所以，你必须成为时间的主人，而不是它的奴仆，作为刚入学的大学生，妥善安排时间是你的头等大事。 3 Time is valuable. Wasting time is a bad habit. It is like a drug. The more time you waste,the easier it is to go on wasting time. If seriously wish to get the most out of college, you must put the time message into practice. 译：时间是珍贵的，浪费时间是个坏习惯，这就像毒品一样，你越浪费时间，就越容易继续浪费下去，如果你真的想充分利用上大学的机会，你就应该把利用时间的要旨付诸实践。 Message1. Control time from the beginning. 4 Time is today, not tomorrow or next week. Start your plan at the Beginning of the term. 译：抓紧时间就是抓紧当前的时间，不要把事情推到明天或是下周，在学期开始就开始计划。 Message2. Get the notebook habit. 5 Go and buy a notebook today, Use it to plan your study time each day. Once a weekly study plan is prepared, follow the same pattern every week with small changes. Sunday is a good day to make the Plan for the following week.
Exploring Filipino School Counselors’ Beliefs about Learning Allan B. I. Bernardo [Abstract] School reform efforts that focus on student learning require school counselors to take on important new roles as advocates of student learning and achievement.But how do school counselors understand the process of learning? In this study, we explore the learning beliefs of 115 Filipino school counselors who indicated their degree of agreementwith 42 statements about the process of learning and the factors thatinfluence this process.A principal components analysis of the responses to the 42 statements suggested three factors:(F1)social-cognitive constructivist beliefs, (F2) teacher-curriculum-centered behaviorist beliefs,and (F3) individual difference factors.The preliminary results are briefly discussed in terms of issues related to how Filipino school counselors’ conceptions of learning may guide their strategies for promoting student learning and achievement. [Key words]beliefs about learning, conceptions of learning, school counselors, student learning, Philippines School reform efforts in different parts of the world have focusedon students’learning. In particular,most school improvement programsnow aim to ensure that students acquire the high-level knowledge and skills that help them to thrive in today’s highly competitive globaleconomy (e.g., Lee & Williams, 2006). I n this regard, school reform programs draw from various contemporary theories and research on learning (e.g.,Bransford,Brown, & Cocking, 1999; Lambert & McCombs, 1998).The basic idea is that all school improvement efforts should be directed at ensuring students achieve high levels of learning or attainment of well-defined curricular objectives and standards.For example, textbooks (Chien & Young, 2007), computers and educational technology (Gravoso, 2002; Haertnel & Means, 2003;Technology in Schools Task Force, 2003), and educational assessment systems (Black & Wiliam2004; Cheung & Ng, 2007; Clark, 2001; Stiggins, 2005) are being reconsidered as regards how they can effectively provide scaffolds and resources for advancing student learning. Likewise,the allocation and management of a school’s financial resources are assessed in terms ofwhether these are effectively mobilized and utilized towards improving student learning (Bolam, 2006; Chung & Hung, 2006; Retna, 2007). In this regard, some advocates have also called for an examination of the role of school counselors in these reform efforts (Herr, 2002). Inthe United States, House and Hayes (2002) challenged school counselors to take proactive leadership roles in advocating for the success of all
https://www.doczj.com/doc/7314347602.html,/finance/company/consumer.html Consumer finance company The consumer finance division of the SG group of France has become highly active within India. They plan to offer finance for vehicles and two-wheelers to consumers, aiming to provide close to Rs. 400 billion in India in the next few years of its operations. The SG group is also dealing in stock broking, asset management, investment banking, private banking, information technology and business processing. SG group has ventured into the rapidly growing consumer credit market in India, and have plans to construct a headquarters at Kolkata. The AIG Group has been approved by the RBI to set up a non-banking finance company (NBFC). AIG seeks to introduce its consumer finance and asset management businesses in India. AIG Capital India plans to emphasize credit cards, mortgage financing, consumer durable financing and personal loans. Leading Indian and international concerns like the HSBC, Deutsche Bank, Goldman Sachs, Barclays and HDFC Bank are also waiting to be approved by the Reserve Bank of India to initiate similar operations. AIG is presently involved in insurance and financial services in more than one hundred countries. The affiliates of the AIG Group also provide retirement and asset management services all over the world. Many international companies have been looking at NBFC business because of the growing consumer finance market. Unlike foreign banks, there are no strictures on branch openings for the NBFCs. GE Consumer Finance is a section of General Electric. It is responsible for looking after the retail finance operations. GE Consumer Finance also governs the GE Capital Asia. Outside the United States, GE Consumer Finance performs its operations under the GE Money brand. GE Consumer Finance currently offers financial services in more than fifty countries. The company deals in credit cards, personal finance, mortgages and automobile solutions. It has a client base of more than 118 million customers throughout the world
GRA VITY RETAINING?WALL 1. INTRODUCTION Retaining walls are structures used to provide stability for earth or other material where conditions disallow the mass to assume its natural slope, and are commonly used to hold back or support soilbanks,coal or ore piles, and water. Retaining walls are classified, based on the method of achieving stability, into six principal types (Fig.1). The gravity-wall depends upon its weight, as the name implies, for stability. The cantilever wall is a reinforced-concrete wall that utilizes cantilever action to retain the mass behind the wall from assuming a natural slope. Stability of this wall is partially achieved from the weight of soil on the heel portion of the base slab. A counterfort retaining wall is similar to a cantilever retaining wall, except that it is used where the cantilever is long or for very high pressures behind wall and has counterforts, which tie the wall and base together, built at intervals along the wall to reduce the bending moments and sheers. As indicated in Fig.1c, the counterfort is behind the wall and subjected to tensile forces. A buttressed retaining wall is similar to a counterfort wall, except that the bracing is in front of the wall and is in compression instead of tension. Two other types of walls not considered further are crib walls, which are built-up members of pieces of precast concrete, metal, or timber and are supported by anchor pieces embedded in the soil for stability, and semigravity walls, which are walls intermediate between a true gravity and a cantilever wall. (a)(b)(e)
高速视频处理系统中的信号完整性分析 摘要：结合高速DSP图像处理系统讨论了高速数字电路中的信号完整性问题，分析了系统中信号反射、串扰、地弹等现象破坏信号完整性的原因，通过先进IS工具的辅助设计，找出了确保系统信号完整性的具体方法。 关键词：高速电路设计信号完整性 DSP系统 深亚微米工艺在IC设计中的使用使得芯片的集成规模更大、体积越来越小、引脚数越来越多；由于近年来IC工艺的发展，使得其速度越来越高。从而，使得信号完整性问题引起电子设计者广泛关注。 在视频处理系统中，多维并行输入输出信号的频率一般都在百兆赫兹以上，而且对时序的要求也非常严格。本文以DSP图像处理系统为背景，对信号完整性进行准确的理论分析，对信号完整性涉及的典型问题[1]——不确定状态、传输线效应、反射、串扰、地弹等进行深入研究，并且从实际系统入手，利用IS仿真软件寻找有效的途径，解决系统的信号完整性问题。 1 系统简介 为了提高算法效率，实时处理图像信息，本图像处理系统是基于DSP+FPGA结构设计的。系统由SAA7111A视频解码器、TI公司的TMS320C6701 DSP、Altera公司的EPlK50QC208 FPGA、PCI9054 PCI接口控制器以及SBRAM、SDRAM、FIFO、FLASH等构成。FPGA是整个系统的时序控制中心和数据交换的桥梁，而且能够对图像数据实现快速底层处理。DSP是整个系统实时处理高级算法的核心器件。系统结构框图如图1所示。 在整个系统中，PCB电路板的面积仅为15cm×l5cm，系统时钟频率高达167MHz，时钟沿时间为0．6ns。由于系统具有快斜率瞬变和极高的工作频率以及很大的电路密度，使得如何处理高速信号问题成为一个制约设计成功的关键因素。 2 系统中信号完整性问题及解决方案 2．1 信号完整性问题产生机理 信号的完整性是指信号通过物理电路传输后，信号接收端看到的波形与信号发送端发送的波形在容许的误差范围内保持一致，并且空间邻近的传输信号间的相互影响也在容许的范围之内。因此，信号完整性分析的主要目标是保证高速数字信号可靠的传输。实际信号总是存在电压的波动，如图2所示。在A、B两点由于过冲和振铃[2]的存在使信号振幅落入阴影部分的不确定区，可能会导致错误的逻辑电平发生。总线信号传输的情况更加复杂，任何一个信号发生相位上的超前或滞后都可能使总线上数据出错，如图3所示。图中，CLK为时钟信号，D0、D1、D2、D3是数据总线上的信号，系统允许信号最大的建立时间[1]为△t。在正常情况下，D0、D1、D2、D3信号建立时间△t1<△t，在△t时刻之后数据总线的数据已稳定，系统可以从总线上采样到正确的数据，如图3(a)所示。相反，当信号D1、D2、D3受过冲和振铃等信号完整问题干扰时，总线信号就发生
Lesson 1 I’m not feeling well. Let’s talk （M=Mom, T= Tom） M: What,'s the matter, Tom T: I'm not feeling well, Mom M: Do you have a cold T: Yes, I think so. Could you give me some water, please M: Here you are. T: Thank you, Mom. M: Tom, you must go and see a doctor. T: OK, Mom. M: It's cold outside. You must wear your coat. T: OK, Mom. Could you pass me my coat,please M: Here you are. T: Thank you, Mom M: Tell me your teacher's number. I'll call him and tell him you are sick. T: OK. Here it is. 译文 (M=妈妈,T=汤姆) 妈妈:怎么了,汤姆 汤姆:我感觉不舒服,妈妈。 妈妈:你感冒了吗 汤姆:是的,我想是这样的。您能给我一些水吗 妈妈:给你。 汤姆:谢谢您,妈妈。 妈妈:汤姆,你必须去看医生. 汤姆:好的,妈妈。 妈妈:外面很冷。你必须穿你的外套。 汤姆:好的,妈妈。您能把我的外套递给我吗 妈妈:给你。 汤姆:谢谢您,妈妈。 妈妈:告诉我你老师的电话号码。我将给他打电话告诉他你生病了。
文档简介 一，英语翻译经典文章之英文原稿二，中文翻译：这篇英语文章的最好翻译版本！不是俺说的，是俺老师说哒！！ 英文原稿Brian It seems my only request (“please, let me sleep”) is not clear enough, so I made this simple table that can help you when you’re in doubt. Especially during the night
中文翻译小子： 我只想好好地睡觉，你不明白吗？！所以，我做了这个简表。当你不知道怎么办时，特 别是在晚上的时候，你可以看看它。 具体情况行动指南 1，我正在睡觉禁止进入 2，你不确定我是否睡觉，你想搞清楚管你“鸟”事；禁止进入 3，你嗑了药，想奔向我的床你他妈的滚远点 4，你在youtube上看了一个超赞的视频，禁止进入；在脸书上把链接发给我想让我看看 5，就算第三次世界大战开始了管我屁事，他妈的别进来 6，你和你的基友们想和我“玩玩”抱歉，直男一枚。不要碰我的任何东西，门都别碰 7，你想整理我的房间我谢谢你了！我自己会打扫 8，普京宣布同性婚姻合法化终于等到“它”！还好你没放弃！还是不要来我房里！ 9，我不在家进我房间，想都别想 10，白天，我在家。你敲了门，我说“请进” 你可以进来了 福利放送！！
如果你已经看到了这里，那么说明你应该是英文爱好者哦。 下面有一些非常实用，我精心整理的英文资料，你一定用得到！快去看看吧！ 一，最常用英语翻译政治文体句型总结大全完美版 二，英文合同翻译最常用句型总结专业版 三，英语毕业论文提纲模板优秀完整详细无敌版
南京师范大学泰州学院 英文翻译原文 年级： 2011级学号：12110330 姓名：申佳佳 系部：信息工程学院 专业：通信工程 题目：基于C51的数字测速仪设计与仿真 指导教师：焦蓬蓬 2015 年 4 月 5 日
Linux - Operating system of cybertimes Though for a lot of people , regard Linux as the main operating system to make u p huge work station group, finish special effects of " Titanic " make , already can be re garded as and show talent fully. But for Linux, this only numerous news one of. Rece ntly, the manufacturers concerned have announced that support the news of Linux to i ncrease day by day, users' enthusiasm to Linux runs high unprecedentedly too. Then, Linux only have operating system not free more than on earth on 7 year this piece wh at glamour, get the favors of such numerous important software and hardware manufa cturers as the masses of users and Orac le , Informix , HP , Sybase , Corel , Intel , Net scape , Dell ,etc. , OK? 1.The background of Linux and characteristic Linux is a kind of " free (Free ) software ": What is called free, mean users can o btain the procedure and source code freely , and can use them freely , including revise or copy etc.. It is a result of cybertimes, numerous technical staff finish its research a nd development together through Inte rnet, countless user is it test and except fault , c an add user expansion function that oneself make conveniently to participate in. As th e most outstanding one in free software, Linux has characteristic o f the following: (1)Totally follow POSLX standard, expand the network operating system of sup porting all AT&T and BSD Unix characteristic. Because of inheritting Unix outstandi ng design philosophy , and there are clean , stalwart , high-efficient and steady kernels , their all key codes are finished by Li nus Torvalds and other outstanding programmer s, without any Unix code of AT&T or Berkeley, so Linu x is not Unix, but Linux and Unix are totally compatible. (2)Real many tasks, multi-user's system, the built-in n etwork supports, can be with such seamless links as NetWare , Windows NT , OS/2 , Unix ,etc.. Network in various kinds of Unix it tests to be fastest in comparing and ass ess efficiency. Support such many kinds of files systems as FAT16 , FAT32 , NTFS , E x t2FS , ISO9600 ,etc. at the same time .
Basic Control Actions and Industrial Automatic Control An automatic controller compares the actual value of the plant output with the desired value, determines the deviation, and produces a control signal which will reduce the deviation to zero or to a small value.The manner in which the automatic conroller produces the control signal is called the control action. Classifications of industrial automatic controllers Induetrial automatic controllers may be classified according to their control action as: ·two-position or on-off controllers; ·proportional controllers; ·integral controllers; ·proportional-plus-integral controllers; ·proportional-plus-derivative controllers; ·proportional-plus-derivative-plus-integral controllers. Most industrial automatic controllers use eletricity or pressurized fluid such as oil or air as power sources. Automatic controllers may also be classified according to the kind of power employed in the operation, such as pneumatic controllers, hydraulic controllers, or electronic controllers.What kind of controller to use must be decided by the nature of the plant and the operating conditions,including such considerations as safety, availability, reliability, accuracy, weight, and size? Elements of industrial automatic controllers An automatic controller must detect the actuating error signal, which is usually at a very low power level, and amplify it to a sufficiently high level. Thus, an amplifier is necessary. The output of an automatic controller is fed to a power device, such as a pneumatic motor or valve, a hydraulic motor, or an electric motor. The controller usually consists of an error detector and amplifier. The measuring element is a device that converts the output variable into another suitable variable, such as a displacement, pressure, or electric signal, which can be used for comparing the output to the reference input signal. This element is in the feedback path of the closed-loop system. The set point of the controller must be converted to a reference input of the same units as the feedback signal from the measuring element. The amplifier amplifies the power of the actuating error signal, which in turn operates the actuator. The actuator is an element which alters the input to the plant according to the control signal so that the feedback signal may be brought into correspondence with the reference input signal. Self-operated controllers In most industrial automatic controllers, separate units are used for the measuring element and for the actuator. In a very simple one, however, such as a self-operated controller, these elements are assembled in one unit. Self-operated controllers utilize power developed by the measuring element and are very simple and inexpensive. The set point is determined by the adjustment of the spring force. The controlled pressure is measured by the diaphragm. The actuating error signal is the net force acting on the diaphragm. Its position determines the valve opening. The operation of self-operated controller is as follows: Suppose that the output pressure is lower than the reference pressure, as determined by the set point. Then the downward spring force is greater than the upward pressure force, resulting in a downward movement of the diaphragm. This increases the flow rate and raises the output pressure.
Engineering with Computers(2002)18:109–115 Ownership and Copyright ?2002Springer-Verlag London Limited Structural Optimization of Automotive Body Components Based on Parametric Solid Modeling M.E.Botkin GM R&D Center,Warren,MI,USA Abstract Abstract::Parametric modeling was used to build several models of an automotive front structure concept that utilizes carbon fiber composite materials and the corresponding molding processes.An ultra-lightweight aluminum body front structure was redesigned to include an all-composite front structure.Two alternative concepts were studied which represent the structure as a bonded assembly of shells.Closed sections result from two pieces–an inner and outer.Parametric modeling was found to be a useful tool for building and modifying models to use in optimization concept studies. Such models can be built quickly and both the sketch dimensions and location dimensions are particularly useful for making the adjustments necessary to fit the various body pieces together.The parametric models then must be joined together as one geometric solid model in order to obtain a surface mesh.Structural optimization input data can then be seamlessly and quickly created from the parametric-modelbased finite element model to begin the tradeoff studies.This integrated process in which parametric modeling was coupled with structural optimization was used to carry out design studies on the lightweight body front structure.Several carbon fiber material combinations were studied to determine mass reduction potential of certain types of carbon fiber products considered to be lower cost than typical carbon fiber materials used in the past.Structural optimization was used to compare several composite constructions for the design of the bonded front structure.Eight cases were studied using various materials and composite lay-ups.Mass savings estimates from45–64%over steel were obtained.The most reasonable design consisted of a combination of relatively low cost chopped carbon fiber and woven carbon fiber and using a20mm balsa core in the top of the shock tower area. This design had a maximum thickness of7mm and a mass reduction over steel of approximately62%.Correspondence and offprint requests to:Mark E.Botkin,Principal