毕业设计外文翻译-中文版
毕业论文(设计)外文文献翻译及原文
金融体制、融资约束与投资——来自OECD的实证分析R.SemenovDepartment of Economics,University of Nijmegen,Nijmegen(荷兰内梅亨大学,经济学院)这篇论文考查了OECD的11个国家中现金流量对企业投资的影响.我们发现不同国家之间投资对企业内部可获取资金的敏感性具有显著差异,并且银企之间具有明显的紧密关系的国家的敏感性比银企之间具有公平关系的国家的低.同时,我们发现融资约束与整体金融发展指标不存在关系.我们的结论与资本市场信息和激励问题对企业投资具有重要作用这种观点一致,并且紧密的银企关系会减少这些问题从而增加企业获取外部融资的渠道。
一、引言各个国家的企业在显著不同的金融体制下运行。
金融发展水平的差别(例如,相对GDP的信用额度和相对GDP的相应股票市场的资本化程度),在所有者和管理者关系、企业和债权人的模式中,企业控制的市场活动水平可以很好地被记录.在完美资本市场,对于具有正的净现值投资机会的企业将一直获得资金。
然而,经济理论表明市场摩擦,诸如信息不对称和激励问题会使获得外部资本更加昂贵,并且具有盈利投资机会的企业不一定能够获取所需资本.这表明融资要素,例如内部产生资金数量、新债务和权益的可得性,共同决定了企业的投资决策.现今已经有大量考查外部资金可得性对投资决策的影响的实证资料(可参考,例如Fazzari(1998)、 Hoshi(1991)、 Chapman(1996)、Samuel(1998)).大多数研究结果表明金融变量例如现金流量有助于解释企业的投资水平。
这项研究结果解释表明企业投资受限于外部资金的可得性。
很多模型强调运行正常的金融中介和金融市场有助于改善信息不对称和交易成本,减缓不对称问题,从而促使储蓄资金投着长期和高回报的项目,并且提高资源的有效配置(参看Levine(1997)的评论文章)。
因而我们预期用于更加发达的金融体制的国家的企业将更容易获得外部融资.几位学者已经指出建立企业和金融中介机构可进一步缓解金融市场摩擦。
本科毕业设计外文翻译(中文)
本科生毕业设计(论文)外文翻译外文原文题目:Real-time interactive optical micromanipulation of a mixture of high- and low-index particles中文翻译题目:高低折射率微粒混合物的实时交互式光学微操作毕业设计(论文)题目:阵列光镊软件控制系统设计姓名:任有健学院:生命学院班级:06210501指导教师:李勤高低折射率微粒混合物的实时交互式光学微操作Peter John Rodrigo Vincent Ricardo Daria Jesper Glückstad丹麦罗斯基勒DK-4000号,Risø国家实验室光学和等离子研究系jesper.gluckstad@risoe.dkhttp://www.risoe.dk/ofd/competence/ppo.htm摘要:本文论证一种对于胶体的实时交互式光学微操作的方法,胶体中包含两种折射率的微粒,与悬浮介质(0n )相比,分别低于(0L n n <)、高于(0H n n >)悬浮介质的折射率。
球形的高低折射率微粒在横平板上被一批捕获激光束生成的约束光势能捕获,捕获激光束的横剖面可以分为“礼帽形”和“圆环形”两种光强剖面。
这种应用方法在光学捕获的空间分布和个体几何学方面提供了广泛的可重构性。
我们以实验为基础证实了同时捕获又独立操作悬浮于水(0 1.33n =)中不同尺寸的球形碳酸钠微壳( 1.2L n ≈)和聚苯乙烯微珠( 1.57H n =)的独特性质。
©2004 美国光学学会光学分类与标引体系编码:(140.7010)捕获、(170.4520)光学限制与操作和(230.6120)空间光调制器。
1 引言光带有动量和角动量。
伴随于光与物质相互作用的动量转移为我们提供了在介观量级捕获和操作微粒的方法。
过去数十年中的巨大发展已经导致了在生物和物理领域常规光学捕获的各种应用以及下一代光学微操作体系的出现[1-5]。
采矿工程 毕业设计_外文翻译 英译汉 中英文
ROOM-AND-PILLAR METHOD OF OPEN-STOPE MINING空场采矿法中的房柱采矿法Chapter 1.A Classification of the Room-and-Pillar Method of Open-Stope Mining第一部分,空场采矿的房柱法的分类OPEN STOPING空场采矿法An open stope is an underground cavity from which the initial ore has been mined. Caving of the opening is prevented (at least temporarily) by support from the unmined ore or waste left in the stope,in the form of pillars,and the stope walls (also called ribs or abutments). In addition to this primary may also be required using rockbolts , reinforcing rods, split pipes ,or shotcrete to stabilize the rock surface immediately adjacent to the opening. The secondary reinforcement procedure does not preclude the method classified as open stoping.露天采场台阶是开采了地下矿石后形成的地下洞室。
通过块矿或采场的支柱和(也称为肋或肩)采场墙形式的废料的支持来(至少是暂时的)预防放顶煤的开幕。
除了这个,可能还需要使用锚杆,钢筋棒,分流管,或喷浆,以稳定紧邻开幕的岩石表面。
java毕业设计中英文翻译
java毕业设计中英文翻译篇一:JAVA外文文献+翻译Java and the InternetIf Java is, in fact, yet another computer programming language, you may question why it is so important and why it is being promoted as a revolutionary step in computer programming. The answer isn’t immediately obvious if you’re coming from a traditional programming perspective. Although Java is very useful for solving traditional stand-alone programming problems, it is also important because it will solve programming problems on the World Wide Web.1. Client-side programmingThe Web’s initial server-browser design provided for interactive content, but the interactivity was completely provided by the server. The server produced static pages for the client browser, which would simply interpret and display them. Basic HTML contains simple mechanisms for data gathering: text-entry boxes, check boxes, radio boxes, lists and drop-down lists, as well as a button that can only be programmed to reset the data on the form or “submit” the data on the form backto the server. This submission passes through the Common Gateway Interface (CGI) provided on all Web servers. The text within the submission tells CGI what to do with it. The most common action is to run a program located on the server in a directory that’s typically called “cgi-bin.” (If you watch the address window at the top of your browser when you push a button on a Web page, you can sometimes see “cgi-bin” within all the gobbledygook there.) These programs can be written in most languages. Perl is a common choice because it is designed for text manipulation and is interpreted, so it can be installed on any server regardless of processor or operating system. Many powerful Web sites today are built strictly on CGI, and you can in fact do nearly anything with it. However, Web sites built on CGI programs can rapidly become overly complicated to maintain, and there is also the problem of response time. The response of a CGI program depends on how much data mustbe sent, as well as the load on both the server and the Internet. (On top of this, starting a CGI program tends to be slow.) The initial designers of the Web didnot foresee how rapidly this bandwidth would be exhausted for the kinds of applications people developed. For example, any sort of dynamic graphing is nearly impossible to perform with consistency because a GIF file must be created and moved from the server to the client for each version of the graph. And you’ve no doubt had direct experience with something as simple as validating the data on an input form. You press the submit button on a page; the data is shipped back to the server; the server starts a CGI program that discovers an error, formats an HTML page informing you of the error, and then sends the page back to you; you must then back up a page and try again. Not only is this slow, it’s inelegant.The solution is client-side programming. Most machines that run Web browsers are powerful engines capable of doing vast work, and with the original static HTML approach they are sitting there, just idly waiting for the server to dish up the next page. Client-side programming means that the Web browser is harnessed to do whatever work it can, and the result for the user is a much speedier and more interactive experience atyour Web site.The problem with discussions of client-side programming is that they aren’t very different from discussions of programming in general. The parameters are almost the same, but the platform is different: a Web browser is like a limited operating system. In the end, you must still program, and this accounts for the dizzying array of problems and solutions produced by client-side programming. The rest of this section provides an overview of the issues and approaches in client-side programming.2.Plug-insOne of the most significant steps forward in client-side programming is the development of the plug-in. This is a way for a programmer to add new functionality to the browser by downloading a piece of code that plugs itself into the appropriate spot in the browser. It tells the browser “from now on you can perform this new activity.” (You need to download the plug-in only once.) Some fast and powerful behavior is added to browsers via plug-ins, but writing a plug-in is not a trivial task, and isn’t something you’d wantto do as part of the process of building a particular site. The value of the plug-in for client-side programming is that it allows an expert programmer to develop a new language and add that language to a browser without the permission of the browser manufacturer. Thus, plug-ins provide a “back door”that allows the creation of new client-side programming languages (although not all languages are implemented as plug-ins).3.Scripting languagesPlug-ins resulted in an explosion of scripting languages. With a scripting language you embed the source code for your client-side program directly into the HTML page, and the plug-in that interprets that language is automatically activated while the HTML page is being displayed. Scripting languages tend to be reasonably easy to understand and, because they are simply text that is part of an HTML page, they load very quickly as part of the single server hit required to procure that page. The trade-off is that your code is exposed for everyone to see (and steal). Generally, however, you aren’t doing amazingly sophisticatedthings with scripting languages so this is not too much of a hardship.This points out that the scripting languages used inside Web browsers are really intended to solve specific types of problems, primarily the creation of richer and more interactive graphical user interfaces (GUIs). However, a scripting language might solve 80 percent of the problems encountered in client-side programming. Your problems might very well fit completely within that 80 percent, and since scripting languages can allow easier and faster development, you should probably consider a scripting language before looking at a more involved solution such as Java or ActiveX programming.The most commonly discussed browser scripting languages are JavaScript (which has nothing to do with Java; it’s named that way just to grab some of Java’s marketing momentum), VBScript (which looks like Visual Basic), andTcl/Tk, which comes from the popular cross-platform GUI-building language. There are others out there, and no doubt more in development.JavaScript is probably the most commonly supported. It comes built into both Netscape Navigator and the Microsoft Internet Explorer (IE). In addition, there are probably more JavaScript books available than there are for the other browser languages, and some tools automatically create pages using JavaScript. However, if you’re already fluent in Visual Basic or Tcl/Tk, you’ll be more productive using those scripting languages rather than learning a new one. (You’ll have your hands full dealing with the Web issues already.)4.JavaIf a scripting language can solve 80 percent of the client-side programming problems, what about the other 20 percent—the “really hard stuff?” The most popular solution today is Java. Not only is it a powerful programming language built to be secure, cross-platform, and international, but Java is being continually extended to provide language features and libraries that elegantly handle problems that are difficult in traditional programming languages, such as multithreading, database access, network programming, and distributed computing. Java allowsclient-side programming via the applet.An applet is a mini-program that will run only under a Web browser. The applet is downloaded automatically as part of a Web page (just as, for example, a graphic is automatically downloaded). When the applet is activated it executes a program. This is part of its beauty—it provides you with a way to automatically distribute the client software from the server at the time the user needs the client software, and no sooner. The user gets the latest version of the client software without fail and without difficult reinstallation. Because of the way Java is designed, the programmer needs to create only a single program, and that program automatically works with all computers that have browsers with built-in Java interpreters. (This safely includes the vast majority of machines.) Since Java is a full-fledged programming language, you can do as much work as possible on the client before and after making requests of theserver. For example, you won’t need to send a request form across the Internet to discover that you’ve gotten a date or some other parameter wrong, and yourclient computer can quickly do the work of plotting data instead of waiting for the server to make a plot and ship a graphic image back to you. Not only do you get the immediate win of speed and responsiveness, but the general network traffic and load on servers can be reduced, preventing the entire Internet from slowing down.One advantage a Java applet has over a scripted program is that it’s in compiled form, so the source code isn’t available to the client. On the other hand, a Java applet can be decompiled without too much trouble, but hiding your code is often not an important issue. Two other factors can be important. As you will see later in this book, a compiled Java applet can comprise many modules and take multiple server “hits” (accesses) to download. (In Java 1.1 and higher this is minimized by Java archives, called JAR files, that allow all the required modules to be packaged together and compressed for a single download.) A scripted program will just be integrated into the Web page as part of its text (and will generally be smaller and reduce server hits). This could be important to the responsiveness of your Website. Another factor is the all-important learning curve. Regardless of what you’ve heard, Java is not a trivial language to learn. If you’re a Visual Basic programmer, moving to VBScript will be your fastest solution, and since it will probably solve most typical client/server problems you might be hard pressed to justify learning Java. If you’re experienced with a scripting language you will certainly benefit from looking at JavaScript or VBScript before committing to Java, since they might fit your needs handily and you’ll be more productive sooner.to run its applets withi5.ActiveXTo some degree, the competitor to Java is Microsoft’s ActiveX, although it takes a completely different approach. ActiveX was originally a Windows-only solution, although it is now being developed via an independent consortium to become cross-platform. Effectively, ActiveX says “if your program connects to篇二:JAVA思想外文翻译毕业设计文献来源:Bruce Eckel. Thinking in Java [J]. Pearson Higher Isia Education,XX-2-20.Java编程思想 (Java和因特网)既然Java不过另一种类型的程序设计语言,大家可能会奇怪它为什么值得如此重视,为什么还有这么多的人认为它是计算机程序设计的一个里程碑呢?如果您来自一个传统的程序设计背景,那么答案在刚开始的时候并不是很明显。
毕业设计中英文翻译
本科生毕业设计(论文)外文翻译毕业设计(论文)题目:电力系统检测与计算外文题目:The development of the single chipmicrocomputer译文题目:单片机技术的发展与应用学生姓名: XXX专业: XXX指导教师姓名: XXX评阅日期:单片机技术的发展与应用从无线电世界到单片机世界现代计算机技术的产业革命,将世界经济从资本经济带入到知识经济时代。
在电子世界领域,从 20 世纪中的无线电时代也进入到 21 世纪以计算机技术为中心的智能化现代电子系统时代。
现代电子系统的基本核心是嵌入式计算机系统(简称嵌入式系统),而单片机是最典型、最广泛、最普及的嵌入式系统。
一、无线电世界造就了几代英才。
在 20 世纪五六十年代,最具代表的先进的电子技术就是无线电技术,包括无线电广播,收音,无线通信(电报),业余无线电台,无线电定位,导航等遥测、遥控、遥信技术。
早期就是这些电子技术带领着许多青少年步入了奇妙的电子世界,无线电技术展示了当时科技生活美妙的前景。
电子科学开始形成了一门新兴学科。
无线电电子学,无线通信开始了电子世界的历程。
无线电技术不仅成为了当时先进科学技术的代表,而且从普及到专业的科学领域,吸引了广大青少年,并使他们从中找到了无穷的乐趣。
从床头的矿石收音机到超外差收音机;从无线电发报到业余无线电台;从电话,电铃到无线电操纵模型。
无线电技术成为当时青少年科普、科技教育最普及,最广泛的内容。
至今,许多老一辈的工程师、专家、教授当年都是无线电爱好者。
无线电技术的无穷乐趣,无线电技术的全面训练,从电子学基本原理,电子元器件基础到无线电遥控、遥测、遥信电子系统制作,培养出了几代科技英才。
二、从无线电时代到电子技术普及时代。
早期的无线电技术推动了电子技术的发展,其中最主要的是真空管电子技术向半导体电子技术的发展。
半导体电子技术使有源器件实现了微小型化和低成本,使无线电技术有了更大普及和创新,并大大地开阔了许多非无线电的控制领域。
毕业设计(论文)外文资料翻译(学生用)
毕业设计外文资料翻译学院:信息科学与工程学院专业:软件工程姓名: XXXXX学号: XXXXXXXXX外文出处: Think In Java (用外文写)附件: 1.外文资料翻译译文;2.外文原文。
附件1:外文资料翻译译文网络编程历史上的网络编程都倾向于困难、复杂,而且极易出错。
程序员必须掌握与网络有关的大量细节,有时甚至要对硬件有深刻的认识。
一般地,我们需要理解连网协议中不同的“层”(Layer)。
而且对于每个连网库,一般都包含了数量众多的函数,分别涉及信息块的连接、打包和拆包;这些块的来回运输;以及握手等等。
这是一项令人痛苦的工作。
但是,连网本身的概念并不是很难。
我们想获得位于其他地方某台机器上的信息,并把它们移到这儿;或者相反。
这与读写文件非常相似,只是文件存在于远程机器上,而且远程机器有权决定如何处理我们请求或者发送的数据。
Java最出色的一个地方就是它的“无痛苦连网”概念。
有关连网的基层细节已被尽可能地提取出去,并隐藏在JVM以及Java的本机安装系统里进行控制。
我们使用的编程模型是一个文件的模型;事实上,网络连接(一个“套接字”)已被封装到系统对象里,所以可象对其他数据流那样采用同样的方法调用。
除此以外,在我们处理另一个连网问题——同时控制多个网络连接——的时候,Java内建的多线程机制也是十分方便的。
本章将用一系列易懂的例子解释Java的连网支持。
15.1 机器的标识当然,为了分辨来自别处的一台机器,以及为了保证自己连接的是希望的那台机器,必须有一种机制能独一无二地标识出网络内的每台机器。
早期网络只解决了如何在本地网络环境中为机器提供唯一的名字。
但Java面向的是整个因特网,这要求用一种机制对来自世界各地的机器进行标识。
为达到这个目的,我们采用了IP(互联网地址)的概念。
IP以两种形式存在着:(1) 大家最熟悉的DNS(域名服务)形式。
我自己的域名是。
所以假定我在自己的域内有一台名为Opus的计算机,它的域名就可以是。
本科毕业设计(论文)外文翻译
重金属污染存在于很多工业的废水中,如电镀,采矿,和制革。
2.实验
2.1化学药剂
本实验所使用的药剂均为分析纯,如无特别说明均购买自日本片山化工。铅离子储备液通过溶解Pb(NO3)2配制,使用时稀释到需要的浓度。HEPES缓冲液购买自Sigma–Aldrich。5 mol/L的HCl和NaOH用来调整pH。
附5
华南理工大学
本科毕业设计(论文)翻译
班级2011环境工程一班
姓名陈光耀
学号201130720022
指导教师韦朝海
填表日期
中文译名
(1)巯基改性纤维素对葡萄糖溶液中铅的吸附(2)黄原酸化橘子皮应用于吸附水中的铅离子
外文原文名
(1)Adsorption of Pb(II) from glucose solution on thiol-functionalized cellulosic biomass
2.5分析方法
铅离子的浓度用分光光度计在616 nm波长处用铅与偶氮氯膦-III络合物进行分析。葡萄糖含量采用苯酚—硫酸分光光度法测定。所有的实验均进行三次,已经考虑好误差。
3.结果和讨论
3.1FTIR分析和改性脱脂棉对铅(II)的吸附机制
图1是脱脂棉、改性脱脂棉在400-4000 cm-1(A)和2540-2560 cm-1(B)范围内的红外光谱图。可以看出,改性后改性脱脂棉的红外光谱图中在1735.71 cm-1处出现了一个新的吸收峰是酯基C=O的拉伸振动峰,可见改性脱脂棉中已经成功引入巯基官能团。同时,在2550.52 cm-1出现的一个新吸收峰代表的是S-H官能团的弱吸收峰,更深一层的证明了巯基已经嫁接到脱脂棉上。图1(b)是2540-2560 cm-1光谱范围的一个放大图像,可以清楚的观察到S-H官能团的弱吸收峰。进一步证明了酯化改性脱脂棉引入巯基是成功的。而从吸附后的曲线可以看到,2550.52cm-1处S-H的吸收峰消失,证明了硫原子和Pb(II)络合物的形成,同时1735.71cm-1处C=O的吸收峰强度看起来有轻微的减弱可能也是和Pb(II)的络合吸附有关。
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。
华南理工大学 毕业设计 外文翻译
华南理工大学本科毕业设计(论文)翻译班级土木工程三班姓名王剑锋学号 200930132042指导教师骆冠勇填表日期 2013年4月21日中文译名一种用于预测拉森钢板桩弯曲强度的数值模型外文原文名 A numerical model for predicting the bending strength of Larssen steel sheetpiles外文原文版出处Journal of Constructional Steel Research 58 (2002) 1361–1374译文:一种用于预测拉森钢板桩弯曲强度的数值模型R.J. Crawford, M.P. Byfield摘要拉森桩为U形横截面并通过可滑动的接头连接在一起组成码头岸壁,围堰,和其他类型的挡土墙。
由于滑动接头位于桩墙的中心线上,相互连接桩的桩间滑移可能导致桩墙70%的弯曲强度折减。
这种桩间滑移可以通过安装成对的带有卷曲的锁头的桩来部分阻止。
然而,像非卷曲桩一样弯曲强度很难被预测,因为这种联锁桩依然存在桩间滑移。
本文提出了一种用于预测联锁拉森桩弯曲应力以及压应力的数值方法。
通过测试1:6比例大小的铝制拉森桩微缩模型的数据与数值模型计算结果进行比较,结果表明数值模型所预测的应力与实际实验结果接近一致。
同时本数值模型也可用于钢板桩的设计生产,以达到使用最少的材料来达到最大的弯曲强度的目的。
C 2002爱思唯尔股份有限公司保留解释权利关键词:行业规范;组合结构;拉森桩;桩结构;挡土墙;钢结构1.介绍钢板桩被广泛运用于全世界。
工程上经常使用的两种钢板桩是U型拉森钢板桩和Z型钢板桩。
两种类型的钢板桩桩都是利用沿着构件长度方向的锁头连接成有缝的连续墙结构。
根据欧洲标准化委员会引入的欧3标准第五部分,U型钢板桩锁头连接部分的下滑位移的影响不能忽视(见图1 步骤1)。
如果钢板桩单肢的相对滑移严重,则钢板桩的弯曲强度会下降到整体强度的70%,我们将其称为钢板桩模量下降。
毕业设计(论文)外文翻译
华南理工大学广州学院本科生毕业设计(论文)翻译外文原文名Agency Cost under the Restriction of Free Cash Flow中文译名自由现金流量的限制下的代理成本学院管理学院专业班级会计学3班学生姓名陈洁玉学生学号200930191100指导教师余勍讲师填写日期2015年5月11日外文原文版出处:译文成绩:指导教师(导师组长)签名:译文:自由现金流量的限制下的代理成本摘要代理成本理论是资本结构理论的一个重要分支。
自由现金流代理成本有显着的影响。
在这两个领域相结合的研究,将有助于建立和扩大理论体系。
代理成本理论基础上,本研究首先分类自由现金流以及统计方法的特点。
此外,投资自由现金流代理成本的存在证明了模型。
自由现金流代理成本理论引入限制,分析表明,它会改变代理成本,进而将影响代理成本和资本结构之间的关系,最后,都会影响到最优资本结构点,以保持平衡。
具体地说,自由现金流增加,相应地,债务比例会降低。
关键词:资本结构,现金流,代理成本,非金钱利益1、介绍代理成本理论,金融契约理论,信号模型和新的啄食顺序理论,新的资本结构理论的主要分支。
财务con-道的理论侧重于限制股东的合同行为,解决股东和债权人之间的冲突。
信令模式和新的啄食顺序理论中心解决投资者和管理者之间的冲突。
这两种类型的冲突是在商业组织中的主要冲突。
代理成本理论认为,如何达到平衡这两种类型的冲突,资本结构是如何形成的,这是比前两次在一定程度上更多的理论更全面。
……Agency Cost under the Restriction of Free Cash FlowAbstractAgency cost theory is an important branch of capital structural theory. Free cash flow has significant impact on agency cost. The combination of research on these two fields would help to build and extend the theoretical system. Based on agency cost theory, the present study firstly categorized the characteristics of free cash flow as well as the statistical methodologies. Furthermore, the existence of investing free cash flow in agency cost was proved by a model. Then free cash flow was introduced into agency cost theory as restriction, the analysis shows that it will change agency cost, in turn, will have an impact on the relationship between agency cost and capital structure, finally, will influence the optimal capital structure point to maintain the equilibrium. Concretely, with the increasing free cash flow, correspondingly, debt proportion will decrease.Keywords:Capital Structure,Free Cash Flow,Agency Cost,Non-Pecuniary Benefit1. IntroductionAgency cost theory, financial contract theory, signaling model and new pecking order theory are the main branches of new capital structure theory. Financial con-tract theory focuses on restricting stockholders’ behavior by contract and solving the conflict between stockholders and creditors. Signaling model and new pecking order theory center on solving the conflict between investors and managers. These two types of conflict are the main conflict in business organizations. Agency cost theory considers how equilibrium is reached in both types of conflict and how capital structure is formed, which is more theory is more comprehensive than the previous two to some degree.……。
土木工程-毕业设计-论文-外文翻译-中英文对照
英文原文:Concrete structure reinforcement designSheyanb oⅠWangchenji aⅡⅠFoundation Engineering Co., Ltd. Heilongjiang DongyuⅡHeilongjiang Province, East Building Foundation Engineering Co., Ltd. CoalAbstract:structure in the long-term natural environment and under the use environment's function, its function is weaken inevitably gradually, our structural engineering's duty not just must finish the building earlier period the project work, but must be able the science appraisal structure damage objective law and the degree, and adopts the effective method guarantee structure the security use, that the structure reinforcement will become an important work. What may foresee will be the 21st century, the human building also by the concrete structure, the steel structure, the bricking-up structure and so on primarily, the present stage I will think us in the structure reinforcement this aspect research should also take this as the main breakthrough direction.Key word:Concrete structure reinforcement bricking-up structure reinforcement steel structure reinforcement1 Concrete structure reinforcementConcrete structure's reinforcement divides into the direct reinforcement and reinforces two kinds indirectly, when the design may act according to the actual condition and the operation requirements choice being suitable method and the necessary technology.1.1the direct reinforcement's general method1)Enlarges the section reinforcement lawAdds the concretes cast-in-place level in the reinforced concrete member in bending compression zone, may increase the section effective height, the expansion cross sectional area, thus enhances the component right section anti-curved, the oblique section anti-cuts ability and the section rigidity, plays the reinforcement reinforcement the role.In the suitable muscle scope, the concretes change curved the component right section supporting capacity increase along with the area of reinforcement and the intensity enhance. In the original component right section ratio of reinforcement not too high situation, increases the main reinforcement area to be possible to propose the plateau component right section anti-curved supporting capacity effectively. Is pulled in the section the area to add the cast-in-place concrete jacket to increase the component section, through new Canada partial and original component joint work, but enhances the component supporting capacity effectively, improvement normal operational performance.Enlarges the section reinforcement law construction craft simply, compatible, and has the mature design and the construction experience; Is suitable in Liang, the board, the column, the wall and the general structure concretes reinforcement; But scene construction's wet operating time is long, to produces has certain influence with the life, and after reinforcing the building clearance has certain reduction.2) Replacement concretes reinforcement lawThis law's merit with enlarges the method of sections to be close, and after reinforcing, does not affect building's clearance, but similar existence construction wet operating time long shortcoming; Is suitable somewhat low or has concretes carrier's and so on serious defect Liang, column in the compression zone concretes intensity reinforcement.3) the caking outsourcing section reinforcement lawOutside the Baotou Steel Factory reinforcement is wraps in the section or the steel plate is reinforced component's outside, outside the Baotou Steel Factory reinforces reinforced concrete Liang to use the wet outsourcing law generally, namely uses the epoxy resinification to be in the milk and so on methods with to reinforce the section the construction commission to cake a whole, after the reinforcement component, because is pulled with the compressed steel cross sectional area large scale enhancement, therefore right section supporting capacity and section rigidity large scale enhancement.This law also said that the wet outside Baotou Steel Factory reinforcement law, the stress is reliable, the construction is simple, the scene work load is small, but is big with the steel quantity, and uses in above not suitably 600C in the non-protection's situation the high temperature place; Is suitable does not allow in the use obviously to increase the original component section size, but requests to sharpen its bearing capacity large scale the concrete structure reinforcement.4) Sticks the steel reinforcement lawOutside the reinforced concrete member in bending sticks the steel reinforcement is (right section is pulled in the component supporting capacity insufficient sector area, right section compression zone or oblique section) the superficial glue steel plate, like this may enhance is reinforced component's supporting capacity, and constructs conveniently.This law construction is fast, the scene not wet work or only has the plastering and so on few wet works, to produces is small with the life influence, and after reinforcing, is not remarkable to the original structure outward appearance and the original clearance affects, but the reinforcement effect is decided to a great extent by the gummy craft and the operational level; Is suitable in the withstanding static function, and is in the normal humidity environment to bend or the tension member reinforcement.5) Glue fibre reinforcement plastic reinforcement lawOutside pastes the textile fiber reinforcement is pastes with the cementing material the fibre reinforcement compound materials in is reinforced the component to pull the region, causes it with to reinforce the section joint work, achieves sharpens the component bearing capacity the goal. Besides has glues the steel plate similar merit, but also has anticorrosive muddy, bears moistly, does not increase the self-weight of structure nearly, durably, the maintenance cost low status merit, but needs special fire protection processing, is suitable in each kind of stress nature concrete structure component and the general construction.This law's good and bad points with enlarge the method of sections to be close; Is suitable reinforcement which is insufficient in the concrete structure component oblique section supporting capacity, or must exert the crosswise binding force to the compressional member the situation.6) Reeling lawThis law's good and bad points with enlarge the method of sections to be close; Is suitable reinforcement which is insufficient in the concrete structure component oblique section supporting capacity, or must exert the crosswise binding force to the compressional member the situation.7) Fang bolt anchor lawThis law is suitable in the concretes intensity rank is the C20~C60 concretes load-bearing member transformation, the reinforcement; It is not suitable for already the above structure which and the light quality structure makes decent seriously. 1.2The indirect reinforcement's general method1)Pre-stressed reinforcement law(1)Thepre-stressed horizontal tension bar reinforces concretes member in bending,because the pre-stressed and increases the exterior load the combined action, in the tension bar has the axial tension, this strength eccentric transmits on the component through the pole end anchor (, when tension bar and Liang board bottom surface close fitting, tension bar can look for tune together with component, this fashion has partial pressures to transmit directly for component bottom surface), has the eccentric compression function in the component, this function has overcome the bending moment which outside the part the load produces, reduced outside the load effect, thus sharpened component's anti-curved ability. At the same time, because the tension bar passes to component's pressure function, the component crack development can alleviate, the control, the oblique section anti-to cut the supporting capacity also along with it enhancement.As a result of the horizontal lifting stem's function, the original component's section stress characteristic by received bends turned the eccentric compression, therefore, after the reinforcement, component's supporting capacity was mainly decided in bends under the condition the original component's supporting capacity 。
毕业设计论文外文文献翻译智能交通信号灯控制中英文对照
英语原文Intelligent Traffic Light Controlby Marco Wiering The topic I picked for our community project was traffic lights. In a community, people need stop signs and traffic lights to slow down drivers from going too fast. If there were no traffic lights or stop signs, people’s lives would be in danger from drivers going too fast.The urban traffic trends towards the saturation, the rate of increase of the road of big city far lags behind rate of increase of the car.The urban passenger traffic has already become the main part of city traffic day by day and it has used about 80% of the area of road of center district. With the increase of population and industry activity, people's traffic is more and more frequent, which is unavoidable. What means of transportation people adopt produces pressure completely different to city traffic. According to calculating, if it is 1 to adopt the area of road that the public transport needs, bike needs 5-7, car needs 15-25, even to walk is 3 times more than to take public transits. So only by building road can't solve the city traffic problem finally yet. Every large city of the world increases the traffic policy to the first place of the question.For example,according to calculating, when the automobile owning amount of Shanghai reaches 800,000 (outside cars count separately ), if it distributes still as now for example: center district accounts for great proportion, even when several loop-lines and arterial highways have been built up , the traffic cannot be improved more than before and the situation might be even worse. So the traffic policy Shanghai must adopt , or called traffic strategy is that have priority to develop public passenger traffic of city, narrow the scope of using of the bicycle progressively , control the scale of growth of the car traffic in the center district, limit the development of the motorcycle strictly.There are more municipals project under construction in big city. the influence on the traffic is greater.Municipal infrastructure construction is originally a good thing of alleviating the traffic, but in the course of constructing, it unavoidably influence the local traffic. Some road sections are blocked, some change into an one-way lane, thus the vehicle can only take a devious route . The construction makes the road very narrow, forming the bottleneck, which seriously influence the car flow.When having stop signs and traffic lights, people have a tendency to drive slower andlook out for people walking in the middle of streets. To put a traffic light or a stop sign in a community, it takes a lot of work and planning from the community and the city to put one in. It is not cheap to do it either. The community first needs to take a petition around to everyone in the community and have them sign so they can take it to the board when the next city council meeting is. A couple residents will present it to the board, and they will decide weather or not to put it in or not. If not put in a lot of residents might be mad and bad things could happened to that part of the city.When the planning of putting traffic lights and stop signs, you should look at the subdivision plan and figure out where all the buildings and schools are for the protection of students walking and riding home from school. In our plan that we have made, we will need traffic lights next to the school, so people will look out for the students going home. We will need a stop sign next to the park incase kids run out in the street. This will help the protection of the kids having fun. Will need a traffic light separating the mall and the store. This will be the busiest part of the town with people going to the mall and the store. And finally there will need to be a stop sign at the end of the streets so people don’t drive too fast and get in a big accident. If this is down everyone will be safe driving, walking, or riding their bikes.In putting in a traffic light, it takes a lot of planning and money to complete it. A traffic light cost around $40,000 to $125,000 and sometimes more depending on the location. If a business goes in and a traffic light needs to go in, the business or businesses will have to pay some money to pay for it to make sure everyone is safe going from and to that business. Also if there is too many accidents in one particular place in a city, a traffic light will go in to safe people from getting a severe accident and ending their life and maybe someone else’s.The reason I picked this part of our community development report was that traffic is a very important part of a city. If not for traffic lights and stop signs, people’s lives would be in danger every time they walked out their doors. People will be driving extremely fast and people will be hit just trying to have fun with their friends. So having traffic lights and stop signs this will prevent all this from happening.Traffic in a city is very much affected by traffic light controllers. When waiting for a traffic light, the driver looses time and the car uses fuel. Hence, reducing waiting times before traffic lights can save our European society billions of Euros annually. To make traffic light controllers more intelligent, we exploit the emergence of novel technologies such as communication networks and sensor networks, as well as the use of more sophisticated algorithms for setting traffic lights. Intelligent traffic light control does not only mean thattraffic lights are set in order to minimize waiting times of road users, but also that road users receive information about how to drive through a city in order to minimize their waiting times. This means that we are coping with a complex multi-agent system, where communication and coordination play essential roles. Our research has led to a novel system in which traffic light controllers and the behaviour of car drivers are optimized using machine-learning methods.Our idea of setting a traffic light is as follows. Suppose there are a number of cars with their destination address standing before a crossing. All cars communicate to the traffic light their specific place in the queue and their destination address. Now the traffic light has to decide which option (ie, which lanes are to be put on green) is optimal to minimize the long-term average waiting time until all cars have arrived at their destination address. The learning traffic light controllers solve this problem by estimating how long it would take for a car to arrive at its destination address (for which the car may need to pass many different traffic lights) when currently the light would be put on green, and how long it would take if the light would be put on red. The difference between the waiting time for red and the waiting time for green is the gain for the car. Now the traffic light controllers set the lights in such a way to maximize the average gain of all cars standing before the crossing. To estimate the waiting times, we use 'reinforcement learning' which keeps track of the waiting times of individual cars and uses a smart way to compute the long term average waiting times using dynamic programming algorithms. One nice feature is that the system is very fair; it never lets one car wait for a very long time, since then its gain of setting its own light to green becomes very large, and the optimal decision of the traffic light will set his light to green. Furthermore, since we estimate waiting times before traffic lights until the destination of the road user has been reached, the road user can use this information to choose to which next traffic light to go, thereby improving its driving behaviour through a city. Note that we solve the traffic light control problem by using a distributed multi-agent system, where cooperation and coordination are done by communication, learning, and voting mechanisms. To allow for green waves during extremely busy situations, we combine our algorithm with a special bucket algorithm which propagates gains from one traffic light to the next one, inducing stronger voting on the next traffic controller option.We have implemented the 'Green Light District', a traffic simulator in Java in which infrastructures can be edited easily by using the mouse, and different levels of road usage can be simulated. A large number of fixed and learning traffic light controllers have already been tested in the simulator and the resulting average waiting times of cars have been plotted and compared. The results indicate that the learning controllers can reduce average waiting timeswith at least 10% in semi-busy traffic situations, and even much more when high congestion of the traffic occurs.We are currently studying the behaviour of the learning traffic light controllers on many different infrastructures in our simulator. We are also planning to cooperate with other institutes and companies in the Netherlands to apply our system to real world traffic situations. For this, modern technologies such as communicating networks can be brought to use on a very large scale, making the necessary communication between road users and traffic lights possible.中文翻译:智能交通信号灯控制马克·威宁我所选择的社区项目主题是交通灯。
自动化专业毕业设计外文翻译--使用连续小波变换在配电系统中故障定位(中文)
中文6710字毕业设计(论文)外文翻译On the use of continuous-wavelet transform for fault location in distributiong power systems使用连续小波变换在配电系统中故障定位出处:International Journal of Electrical Power & Energy Systems, 2006, 28(9): 608-617使用连续小波变换在配电系统中故障定位a a a ab a R L M A C S A 蒂纳雷利布莱特保罗努奇科希博尔盖蒂.,.,.,..,.,.,*a 意大利波洛尼亚viale Risorgimento 2,40136波洛尼亚大学电气工程系,b 意大利 米兰 CESI收于2006年3月31日;接受2006年3月31日摘要该论文说明了连续小波变换(CWT )为分析由于线路故障引起电压瞬变得基本步骤并讨论了其应用于配电系统故障定位。
所进行的分析实现在网络中显示存在相关典型频率的连续小波变换转换信号和特殊路径代替转换小波引起的故障。
本文提出了一种在MV 离散系统中利用以上所提到的相关性确定MV 配电系统故障定位的步骤。
在本文中分析MV 离散系统是准确地以EMPT 模型为代表,以及研究各种故障类型和网络特点。
本文介绍了一些也基本测量概念和故障定位标准系统的分布式结构。
2006年Elsevier 公司有限公司,版权所有。
关键词:故障测距;配电系统;连续小波变换;电磁暂态;分布式测控系统1. 导言近年来中压配电网络的故障定位是一个日益受到重视研究话题, 由于既要最严的质量的要 求并要提供改进测量和监测系统。
此外,在网络需检修的传统程序的基础上增加的安装分布式发电资源自动开关系统。
最有前途的解决这个大家关注问题的方法似乎是在离散系统中运用适当的信号处理技术引起电压/电流瞬变产生的短路事件并记录在一个或更多的位置。
液压专业毕业设计外文翻译(有译文、外文文献)值得收藏哦!
外文原文:The Analysis of Cavitation Problems in the Axial Piston Pumpshu WangEaton Corporation,14615 Lone Oak Road,Eden Prairie, MN 55344This paper discusses and analyzes the control volume of a piston bore constrained by the valve plate in axial piston pumps. The vacuum within the piston bore caused by the rise volume needs to be compensated by the flow; otherwise, the low pressure may cause the cavitations and aerations. In the research, the valve plate geometry can be optimized by some analytical limitations to prevent the piston pressure below the vapor pressure. The limitations provide the design guide of the timings and overlap areas between valve plate ports and barrel kidneys to consider the cavitations and aerations. _DOI: 10.1115/1.4002058_Keywords: cavitation , optimization, valve plate, pressure undershoots1 IntroductionIn hydrostatic machines, cavitations mean that cavities or bubbles form in the hydraulic liquid at the low pressure and collapse at the high pressure region, which causes noise, vibration, and less efficiency.Cavitations are undesirable in the pump since the shock waves formed by collapsed may be strong enough to damage components. The hydraulic fluid will vaporize when its pressure becomes too low or when the temperature is too high. In practice, a number of approaches are mostly used to deal with the problems: (1) raise the liquid level in the tank, (2) pressurize the tank, (3) booster the inlet pressure of the pump, (4) lower the pumping fluid temperature, and (5) design deliberately the pump itself.Many research efforts have been made on cavitation phenomena in hydraulic machine designs. The cavitation is classified into two types in piston pumps: trapping phenomenon related one (which can be preventedby the proper design of the valve plate) and the one observed on the layers after the contraction or enlargement of flow passages (caused by rotating group designs) in Ref. (1). The relationship between the cavitation and the measured cylinder pressure is addressed in this study. Edge and Darling (2) reported an experimental study of the cylinder pressure within an axial piston pump. The inclusion of fluid momentum effects and cavitations within the cylinder bore are predicted at both high speed and high load conditions. Another study in Ref. (3) provides an overview of hydraulic fluid impacting on the inlet condition and cavitation potential. It indicates that physical properties (such as vapor pressure, viscosity, density, and bulk modulus) are vital to properly evaluate the effects on lubrication and cavitation. A homogeneous cavitation model based on the thermodynamic properties of the liquid and steam is used to understand the basic physical phenomena of mass flow reduction and wave motion influences in the hydraulic tools and injection systems (4). Dular et al. (5, 6) developed an expert system for monitoring and control of cavitations in hydraulic machines and investigated the possibility of cavitation erosion by using the computational fluid dynamics (CFD) tools. The erosion effects of cavitations have been measured and validated by a simple single hydrofoil configuration in a cavitation tunnel. It is assumed that the severe erosion is often due to the repeated collapse of the traveling vortex generated by a leading edge cavity in Ref. (7). Then, the cavitation erosion intensity may be scaled by a simple set of flow parameters: the upstream velocity, the Strouhal number, the cavity length, and the pressure. A new cavitation erosion device, called vortex cavitation generator, is introduced to comparatively study various erosion situations (8).More previous research has been concentrated on the valve plate designs, piston, and pump pressure dynamics that can be associated with cavitations in axial piston pumps. The control volume approach and instantaneous flows (leakage) are profoundly studied in Ref. [9]. Berta et al. [10] used the finite volume concept to develop a mathematical model in which the effects of port plate relief grooves have been modeled andthe gaseous cavitation is considered in a simplified manner. An improved model is proposed in Ref. [11] and validated by experimental results. The model may analyze the cylinder pressure and flow ripples influenced by port plate and relief groove design. Manring compared principal advantages of various valve plate slots (i.e., the slots with constant, linearly varying, and quadratic varying areas) in axial piston pumps [12]. Four different numerical models are focused on the characteristics of hydraulic fluid, and cavitations are taken into account in different ways to assist the reduction in flow oscillations [13].The experiences of piston pump developments show that the optimization of the cavitations/aerations shall include the following issues: occurring cavitation and air release, pump acoustics caused by the induced noises, maximal amplitudes of pressure fluctuations, rotational torque progression, etc. However, the aim of this study is to modify the valve plate design to prevent cavitation erosions caused by collapsing steam or air bubbles on the walls of axial pump components. In contrastto literature studies, the research focuses on the development of analytical relationship between the valve plate geometrics and cavitations. The optimization method is applied to analyze the pressure undershoots compared with the saturated vapor pressure within the piston bore.The appropriate design of instantaneous flow areas between the valveplate and barrel kidney can be decided consequently.2 The Axial Piston Pump and Valve PlateThe typical schematic of the design of the axis piston pump is shown in Fig. 1. The shaft offset e is designed in this case to generate stroking containment moments for reducing cost purposes.The variation between the pivot center of the slipper and swash rotating center is shown as a. The swash angle αis the variable that determines the amount of fluid pumped per shaft revolution. In Fig. 1, the n th piston-slipper assembly is located at the angle ofθ. The displacement of the n thnpiston-slipper assembly along the x-axis can be written asx n= R tan(α)sin(θ)+ a sec(α)+ e tan(α) (1)nwhere R is the pitch radius of the rotating group.Then, the instantaneous velocity of the n th piston isx˙n = R 2sec ()αsin (n θ)α+ R tan (α)cos (n θ)ω+ R 2sec ()αsin (α)α + e 2sec ()αα (2)where the shaft rotating speed of the pump is ω=d n θ / dt .The valve plate is the most significant device to constraint flow inpiston pumps. The geometry of intake/discharge ports on the valve plateand its instantaneous relative positions with respect to barrel kidneys areusually referred to the valve plate timing. The ports of the valve plateoverlap with each barrel kidneys to construct a flow area or passage,which confines the fluid dynamics of the pump. In Fig. 2, the timingangles of the discharge and intake ports on the valve plate are listed as(,)T i d δ and (,)B i d δ. The opening angle of the barrel kidney is referred to asϕ. In some designs, there exists a simultaneous overlap between thebarrel kidney and intake/discharge slots at the locations of the top deadcenter (TDC) or bottom dead center (BDC) on the valve plate on whichthe overlap area appears together referred to as “cross -porting” in thepump design engineering. The cross-porting communicates the dischargeand intake ports, which may usually lower the volumetric efficiency. Thetrapped-volume design is compared with the design of the cross-porting,and it can achieve better efficiency 14]. However, the cross-porting isFig. 1 The typical axis piston pumpcommonly used to benefit the noise issue and pump stability in practice.3 The Control Volume of a Piston BoreIn the piston pump, the fluid within one piston is embraced by the piston bore, cylinder barrel, slipper, valve plate, and swash plate shown in Fig. 3. There exist some types of slip flow by virtue of relativeFig. 2 Timing of the valve platemotions and clearances between thos e components. Within the control volume of each piston bore, the instantaneous mass is calculated asM= n V(3)nwhere ρ and n V are the instantaneous density and volumesuch that themass time rate of change can be given asFig. 3 The control volume of the piston boren n n dM dV d V dt dt dtρρ=+ (4) where d n V is the varying of the volume.Based on the conservation equation, the mass rate in the control volume isn n dM q dtρ= (5)where n q is the instantaneous flow rate in and out of one piston. From the definition of the bulk modulus,n dP d dt dtρρβ= (6) where Pn is the instantaneous pressure within the piston bore. Substituting Eqs. (5) and (6) into Eq. (4) yields(?)n n n n n ndP q dV d V w d βθθ=- (7) where the shaft speed of the pump is n d dtθω=. The instantaneous volume of one piston bore can be calculated by using Eq. (1) asn V = 0V + P A [R tan (α)sin (n θ)+ a sec (α) + e tan(α) ] (8)where P A is the piston sectional area and 0V is the volume of eachpiston, which has zero displacement along the x-axis (when n θ=0, π).The volume rate of change can be calculated at the certain swash angle, i.e., α =0, such thattan cos n p n ndV A R d αθθ=()() (9) in which it is noted that the piston bore volume increases or decreaseswith respect to the rotating angle of n θ.Substituting Eqs. (8) and (9) into Eq. (7) yields0[tan()cos()] [tan sin sec tan() ]n P n n n p n q A R dP d V A R a e βαθωθαθαα-=-++()()()(10)4 Optimal DesignsTo find the extrema of pressure overshoots and undershoots in the control volume of piston bores, the optimization method can be used in Eq. (10). In a nonlinear function, reaching global maxima and minima is usually the goal of optimization. If the function is continuous on a closed interval, global maxima and minima exist. Furthermore, the global maximum (or minimum) either must be a local maximum (or minimum) in the interior of the domain or must lie on the boundary of the domain. So, the method of finding a global maximum (or minimum) is to detect all the local maxima (or minima) in the interior, evaluate the maxima (or minima) points on the boundary, and select the biggest (or smallest) one. Local maximum or local minimum can be searched by using the first derivative test that the potential extrema of a function f( · ), with derivative ()f ', can solve the equation at the critical points of ()f '=0 [15].The pressure of control volumes in the piston bore may be found as either a minimum or maximum value as dP/ dt=0. Thus, letting the left side of Eq. (10) be equal to zero yieldstan()cos()0n p n q A R ωαθ-= (11)In a piston bore, the quantity of n q offsets the volume varying and thendecreases the overshoots and undershoots of the piston pressure. In this study, the most interesting are undershoots of the pressure, which may fall below the vapor pressure or gas desorption pressure to cause cavitations. The term oftan()cos()p n A R ωαθ in Eq. (11) has the positive value in the range of intake ports (22ππθ-≤≤), shown in Fig. 2, which means that the piston volume arises. Therefore, the piston needs the sufficient flow in; otherwise, the pressure may drop.In the piston, the flow of n q may get through in a few scenariosshown in Fig. 3: (I) the clearance between the valve plate and cylinder barrel, (II) the clearance between the cylinder bore and piston, (III) the clearance between the piston and slipper, (IV) the clearance between the slipper and swash plate, and (V) the overlapping area between the barrel kidney and valve plate ports. As pumps operate stably, the flows in the as laminar flows, which can be calculated as [16]312IV k k Ln i I k h q p L ωμ==∑ (12)where k h is the height of the clearance, k L is the passage length,scenarios I –IV mostly have low Reynolds numbers and can be regarded k ω is the width of the clearance (note that in the scenario II, k ω =2π· r, in which r is the piston radius), and p is the pressure drop defined in the intake ports as p =c p -n p (13)where c p is the case pressure of the pump. The fluid films through theabove clearances were extensively investigated in previous research. The effects of the main related dimensions of pump and the operating conditions on the film are numerically clarified inRefs. [17,18]. The dynamic behavior of slipper pads and the clearance between the slipper and swash plate can be referred to Refs. [19,20]. Manring et al. [21,22] investigated the flow rate and load carrying capacity of the slipper bearing in theoretical and experimental methods under different deformation conditions. A simulation tool calledCASPAR is used to estimate the nonisothermal gap flow between the cylinder barrel and the valve plate by Huang and Ivantysynova [23]. The simulation program also considers the surface deformations to predict gap heights, frictions, etc., between the piston and barrel andbetween the swash plate and slipper. All these clearance geometrics in Eq.(12) are nonlinear and operation based, which is a complicated issue. In this study, the experimental measurements of the gap flows are preferred. If it is not possible, the worst cases of the geometrics or tolerances with empirical adjustments may be used to consider the cavitation issue, i.e., minimum gap flows.For scenario V, the flow is mostly in high velocity and can be described by using the turbulent orifice equation as((Tn d i d d q c A c A θθ= (14)where Pi and Pd are the intake and discharge pressure of the pump and ()i A θ and ()d A θ are the instantaneous overlap area between barrel kidneys and inlet/discharge ports of the valve plate individually.The areas are nonlinear functions of the rotating angle, which is defined by the geometrics of the barrel kidney, valve plate ports,silencing grooves, decompression holes, and so forth. Combining Eqs.(11) –(14), the area can be obtained as3()K IV A θ==(15)where ()A θ is the total overlap area of ()A θ=()()i d A A θλθ+, and λ is defined as=In the piston bore, the pressure varies from low tohigh while passing over the intake and discharge ports of the valve plates. It is possible that the instantaneous pressure achieves extremely low values during the intake area( 22ππθ-≤≤ shown in Fig. 2) that may be located below the vapor pressure vp p , i.e., n vp p p ≤;then cavitations canhappen. To prevent the phenomena, the total overlap area of ()A θ mightbe designed to be satisfied with30()K IV A θ=≥(16)where 0()A θ is the minimum area of 0()A θ=0()()i d A A θλθ+ and 0λis a constant that is0λ=gaseous form. The vapor pressure of any substance increases nonlinearly with temperature according to the Clausius –Clapeyron relation. With the incremental increase in temperature, the vapor pressure becomes sufficient to overcome particle attraction and make the liquid form bubbles inside the substance. For pure components, the vapor pressure can be determined by the temperature using the Antoine equation as /()10A B C T --, where T is the temperature, and A, B, and C are constants[24].As a piston traverse the intake port, the pressure varies dependent on the cosine function in Eq. (10). It is noted that there are some typical positions of the piston with respect to the intake port, the beginning and ending of overlap, i.e., TDC and BDC (/2,/2θππ=- ) and the zero displacement position (θ =0). The two situations will be discussed as follows:(1) When /2,/2θππ=-, it is not always necessary to maintain the overlap area of 0()A θ because slip flows may provide filling up for the vacuum. From Eq. (16), letting 0()A θ=0,the timing angles at the TDC and BDC may be designed as31cos ()tan()122IV c vpk k i I P k p p h A r L ωϕδωαμ--≤+∑ (17) in which the open angle of the barrel kidney is . There is nocross-porting flow with the timing in the intake port.(2) When θ =0, the function of cos θ has the maximum value, which can provide another limitation of the overlap area to prevent the low pressure undershoots suchthat 30(0)K IVA =≥ (18)where 0(0)A is the minimum overlap area of 0(0)(0)i A A =.To prevent the low piston pressure building bubbles, the vaporpressure is considered as the lower limitation for the pressure settings in Eq. (16). The overall of overlap areas then can be derived to have adesign limitation. The limitation is determined by the leakage conditions, vapor pressure, rotating speed, etc. It indicates that the higher the pumping speed, the more severe cavitation may happen, and then the designs need more overlap area to let flow in the piston bore. On the other side, the low vapor pressure of the hydraulic fluid is preferred to reduce the opportunities to reach the cavitation conditions. As a result, only the vapor pressure of the pure fluid is considered in Eqs. (16)–(18). In fact, air release starts in the higher pressure than the pure cavitation process mainly in turbulent shear layers, which occur in scenario V.Therefore, the vapor pressure might be adjusted to design the overlap area by Eq. (16) if there exists substantial trapped and dissolved air in the fluid.The laminar leakages through the clearances aforementioned are a tradeoff in the design. It is demonstrated that the more leakage from the pump case to piston may relieve cavitation problems.However, the more leakage may degrade the pump efficiency in the discharge ports. In some design cases, the maximum timing angles can be determined by Eq. (17)to not have both simultaneous overlapping and highly low pressure at the TDC and BDC.While the piston rotates to have the zero displacement, the minimum overlap area can be determined by Eq. 18 , which may assist the piston not to have the large pressure undershoots during flow intake.6 ConclusionsThe valve plate design is a critical issue in addressing the cavitation or aeration phenomena in the piston pump. This study uses the control volume method to analyze the flow, pressure, and leakages within one piston bore related to the valve plate timings. If the overlap area developed by barrel kidneys and valve plate ports is not properly designed, no sufficient flow replenishes the rise volume by the rotating movement. Therefore, the piston pressure may drop below the saturated vapor pressure of the liquid and air ingress to form the vapor bubbles. To control the damaging cavitations, the optimization approach is used to detect the lowest pressure constricted by valve plate timings. The analytical limitation of the overlap area needs to be satisfied to remain the pressure to not have large undershoots so that the system can be largely enhanced on cavitation/aeration issues.In this study, the dynamics of the piston control volume is developed by using several assumptions such as constant discharge coefficients and laminar leakages. The discharge coefficient is practically nonlinear based on the geometrics, flow number, etc. Leakage clearances of the control volume may not keep the constant height and width as well in practice due to vibrations and dynamical ripples. All these issues are complicated and very empirical and need further consideration in the future. Theresults presented in this paper can be more accurate in estimating the cavitations with these extensive studies.Nomenclature0(),()A A θθ= the total overlap area between valve plate ports and barrel kidneys 2()mmAp = piston section area 2()mmA, B, C= constantsA= offset between the piston-slipper joint and surface of the swash plate 2()mmd C = orifice discharge coefficiente= offset between the swash plate pivot and the shaft centerline of the pump 2()mmk h = the height of the clearance 2()mmk L = the passage length of the clearance 2()mmM= mass of the fluid within a single piston (kg)N= number of pistonsn = piston and slipper counter,p p = fluid pressure and pressure drop (bar)Pc= the case pressure of the pump (bar)Pd= pump discharge pressure (bar)Pi = pump intake pressure (bar)Pn = fluid pressure within the nth piston bore (bar)Pvp = the vapor pressure of the hydraulic fluid(bar)qn, qLn, qTn = the instantaneous flow rate of each piston(l/min)R = piston pitch radius 2()mmr = piston radius (mm)t =time (s)V = volume 3()mmwk = the width of the clearance (mm)x ,x ˙= piston displacement and velocity along the shaft axis (m, m/s) x y z --=Cartesian coordinates with an origin on the shaft centerline x y z '''--= Cartesian coordinates with an origin on swash plate pivot ,αα=swash plate angle and velocity (rad, rad/s)β= fluid bulk modulus (bar)δδ= timing angle of valve plates at the BDC and TDC (rad),B Tϕ= the open angle of the barrel kidney(rad)ρ= fluid density(kg/m3),θω= angular position and velocity of the rotating kit (rad, rad/s)μ=absolute viscosity(Cp),λλ= coefficients related to the pressure drop外文中文翻译:在轴向柱塞泵气蚀问题的分析本论文讨论和分析了一个柱塞孔与配流盘限制在轴向柱塞泵的控制量设计。
毕业设计英文 翻译(原文)
编号:毕业设计(论文)外文翻译(原文)院(系):桂林电子科技大学专业:电子信息工程学生姓名: xx学号: xxxxxxxxxxxxx 指导教师单位:桂林电子科技大学姓名: xxxx职称: xx2014年x月xx日Timing on and off power supplyusesThe switching power supply products are widely used in industrial automation and control, military equipment, scientific equipment, LED lighting, industrial equipment,communications equipment,electrical equipment,instrumentation, medical equipment, semiconductor cooling and heating, air purifiers, electronic refrigerator, LCD monitor, LED lighting, communications equipment, audio-visual products, security, computer chassis, digital products and equipment and other fields.IntroductionWith the rapid development of power electronics technology, power electronics equipment and people's work, the relationship of life become increasingly close, and electronic equipment without reliable power, into the 1980s, computer power and the full realization of the switching power supply, the first to complete the computer Power new generation to enter the switching power supply in the 1990s have entered into a variety of electronic, electrical devices, program-controlled switchboards, communications, electronic testing equipment power control equipment, power supply, etc. have been widely used in switching power supply, but also to promote the rapid development of the switching power supply technology .Switching power supply is the use of modern power electronics technology to control the ratio of the switching transistor to turn on and off to maintain a stable output voltage power supply, switching power supply is generally controlled by pulse width modulation (PWM) ICs and switching devices (MOSFET, BJT) composition. Switching power supply and linear power compared to both the cost and growth with the increase of output power, but the two different growth rates. A power point, linear power supply costs, but higher than the switching power supply. With the development of power electronics technology and innovation, making the switching power supply technology to continue to innovate, the turning points of this cost is increasingly move to the low output power side, the switching power supply provides a broad space for development.The direction of its development is the high-frequency switching power supply, high frequency switching power supply miniaturization, and switching power supply into a wider range of application areas, especially in high-tech fields, and promote the miniaturization of high-tech products, light of. In addition, the development and application of the switching power supply in terms of energy conservation, resource conservation and environmental protection are of great significance.classificationModern switching power supply, there are two: one is the DC switching power supply; the other is the AC switching power supply. Introduces only DC switching power supply and its function is poor power quality of the original eco-power (coarse) - such as mains power or battery power, converted to meet the equipment requirements of high-quality DC voltage (Varitronix) . The core of the DC switching power supply DC / DC converter. DC switching power supply classification is dependent on the classification of DC / DC converter. In other words, the classification of the classification of the DC switching power supply and DC/DC converter is the classification of essentially the same, the DC / DC converter is basically a classification of the DC switching power supply.DC /DC converter between the input and output electrical isolation can be divided into two categories: one is isolated called isolated DC/DC converter; the other is not isolated as non-isolated DC / DC converter.Isolated DC / DC converter can also be classified by the number of active power devices. The single tube of DC / DC converter Forward (Forward), Feedback (Feedback) two. The double-barreled double-barreled DC/ DC converter Forward (Double Transistor Forward Converter), twin-tube feedback (Double Transistor Feedback Converter), Push-Pull (Push the Pull Converter) and half-bridge (Half-Bridge Converter) four. Four DC / DC converter is the full-bridge DC / DC converter (Full-Bridge Converter).Non-isolated DC / DC converter, according to the number of active power devices can be divided into single-tube, double pipe, and four three categories. Single tube to a total of six of the DC / DC converter, step-down (Buck) DC / DC converter, step-up (Boost) DC / DC converters, DC / DC converter, boost buck (Buck Boost) device of Cuk the DC / DC converter, the Zeta DC / DC converter and SEPIC, the DC / DC converter. DC / DC converters, the Buck and Boost type DC / DC converter is the basic buck-boost of Cuk, Zeta, SEPIC, type DC / DC converter is derived from a single tube in this six. The twin-tube cascaded double-barreled boost (buck-boost) DC / DC converter DC / DC converter. Four DC / DC converter is used, the full-bridge DC / DC converter (Full-Bridge Converter).Isolated DC / DC converter input and output electrical isolation is usually transformer to achieve the function of the transformer has a transformer, so conducive to the expansion of the converter output range of applications, but also easy to achieve different voltage output , or a variety of the same voltage output.Power switch voltage and current rating, the converter's output power is usually proportional to the number of switch. The more the number of switch, the greater the output power of the DC / DC converter, four type than the two output power is twice as large,single-tube output power of only four 1/4.A combination of non-isolated converters and isolated converters can be a single converter does not have their own characteristics. Energy transmission points, one-way transmission and two-way transmission of two DC / DC converter. DC / DC converter with bi-directional transmission function, either side of the transmission power from the power of lateral load power from the load-lateral side of the transmission power.DC / DC converter can be divided into self-excited and separately controlled. With the positive feedback signal converter to switch to self-sustaining periodic switching converter, called self-excited converter, such as the the Luo Yeer (Royer,) converter is a typical push-pull self-oscillating converter. Controlled DC / DC converter switching device control signal is generated by specialized external control circuit.the switching power supply.People in the field of switching power supply technology side of the development of power electronic devices, while the development of the switching inverter technology, the two promote each other to promote the switching power supply annual growth rate of more than two digits toward the light, small, thin, low-noise, high reliability, the direction of development of anti-jamming. Switching power supply can be divided into AC / DC and DC / DC two categories, AC / AC DC / AC, such as inverters, DC / DC converter is now modular design technology and production processes at home and abroad have already matured and standardization, and has been recognized by the user, but AC / DC modular, its own characteristics make the modular process, encounter more complex technology and manufacturing process. Hereinafter to illustrate the structure and characteristics of the two types of switching power supply.Self-excited: no external signal source can be self-oscillation, completely self-excited to see it as feedback oscillation circuit of a transformer.Separate excitation: entirely dependent on external sustain oscillations, excited used widely in practical applications. According to the excitation signal structure classification; can be divided into pulse-width-modulated and pulse amplitude modulated two pulse width modulated control the width of the signal is frequency, pulse amplitude modulation control signal amplitude between the same effect are the oscillation frequency to maintain within a certain range to achieve the effect of voltage stability. The winding of the transformer can generally be divided into three types, one group is involved in the oscillation of the primary winding, a group of sustained oscillations in the feedback winding, there is a group of load winding. Such as Shanghai is used in household appliances art technological production of switching power supply, 220V AC bridge rectifier, changing to about 300V DC filter added tothe collector of the switch into the transformer for high frequency oscillation, the feedback winding feedback to the base to maintain the circuit oscillating load winding induction signal, the DC voltage by the rectifier, filter, regulator to provide power to the load. Load winding to provide power at the same time, take up the ability to voltage stability, the principle is the voltage output circuit connected to a voltage sampling device to monitor the output voltage changes, and timely feedback to the oscillator circuit to adjust the oscillation frequency, so as to achieve stable voltage purposes, in order to avoid the interference of the circuit, the feedback voltage back to the oscillator circuit with optocoupler isolation.technology developmentsThe high-frequency switching power supply is the direction of its development, high-frequency switching power supply miniaturization, and switching power supply into the broader field of application, especially in high-tech fields, and promote the development and advancement of the switching power supply, an annual more than two-digit growth rate toward the light, small, thin, low noise, high reliability, the direction of the anti-jamming. Switching power supply can be divided into AC / DC and DC / DC two categories, the DC / DC converter is now modular design technology and production processes at home and abroad have already matured and standardized, and has been recognized by the user, but modular AC / DC, because of its own characteristics makes the modular process, encounter more complex technology and manufacturing process. In addition, the development and application of the switching power supply in terms of energy conservation, resource conservation and environmental protection are of great significance.The switching power supply applications in power electronic devices as diodes, IGBT and MOSFET.SCR switching power supply input rectifier circuit and soft start circuit, a small amount of applications, the GTR drive difficult, low switching frequency, gradually replace the IGBT and MOSFET.Direction of development of the switching power supply is a high-frequency, high reliability, low power, low noise, jamming and modular. Small, thin, and the key technology is the high frequency switching power supply light, so foreign major switching power supply manufacturers have committed to synchronize the development of new intelligent components, in particular, is to improve the secondary rectifier loss, and the power of iron Oxygen materials to increase scientific and technological innovation in order to improve the magnetic properties of high frequency and large magnetic flux density (Bs), and capacitor miniaturization is a key technology. SMT technology allows the switching power supply has made considerable progress, the arrangement of the components in the circuit board on bothsides, to ensure that the light of the switching power supply, a small, thin. High-frequency switching power supply is bound to the traditional PWM switching technology innovation, realization of ZVS, ZCS soft-switching technology has become the mainstream technology of the switching power supply, and a substantial increase in the efficiency of the switching power supply. Indicators for high reliability, switching power supply manufacturers in the United States by reducing the operating current, reducing the junction temperature and other measures to reduce the stress of the device, greatly improve the reliability of products.Modularity is the overall trend of switching power supply, distributed power systems can be composed of modular power supply, can be designed to N +1 redundant power system, and the parallel capacity expansion. For this shortcoming of the switching power supply running noise, separate the pursuit of high frequency noise will also increase, while the use of part of the resonant converter circuit technology to achieve high frequency, in theory, but also reduce noise, but some The practical application of the resonant converter technology, there are still technical problems, it is still a lot of work in this field, so that the technology to be practical.Power electronics technology innovation, switching power supply industry has broad prospects for development. To accelerate the pace of development of the switching power supply industry in China, it must take the road of technological innovation, out of joint production and research development path with Chinese characteristics and contribute to the rapid development of China's national economy.Developments and trends of the switching power supply1955 U.S. Royer (Roger) invented the self-oscillating push-pull transistor single-transformer DC-DC converter is the beginning of the high-frequency conversion control circuit 1957 check race Jen, Sen, invented a self-oscillating push-pull dual transformers, 1964, U.S. scientists canceled frequency transformer in series the idea of switching power supply, the power supply to the size and weight of the decline in a fundamental way. 1969 increased due to the pressure of the high-power silicon transistor, diode reverse recovery time shortened and other components to improve, and finally made a 25-kHz switching power supply.At present, the switching power supply to the small, lightweight and high efficiency characteristics are widely used in a variety of computer-oriented terminal equipment, communications equipment, etc. Almost all electronic equipment is indispensable for a rapid development of today's electronic information industry power mode. Bipolar transistor made of 100kHz, 500kHz power MOS-FET made, though already the practical switching power supply is currently available on the market, but its frequency to be further improved. Toimprove the switching frequency, it is necessary to reduce the switching losses, and to reduce the switching losses, the need for high-speed switch components. However, the switching speed will be affected by the distribution of the charge stored in the inductance and capacitance, or diode circuit to produce a surge or noise. This will not only affect the surrounding electronic equipment, but also greatly reduce the reliability of the power supply itself. Which, in order to prevent the switching Kai - closed the voltage surge, RC or LC buffers can be used, and the current surge can be caused by the diode stored charge of amorphous and other core made of magnetic buffer . However, the high frequency more than 1MHz, the resonant circuit to make the switch on the voltage or current through the switch was a sine wave, which can reduce switching losses, but also to control the occurrence of surges. This switch is called the resonant switch. Of this switching power supply is active, you can, in theory, because in this way do not need to greatly improve the switching speed of the switching losses reduced to zero, and the noise is expected to become one of the high-frequency switching power supply The main ways. At present, many countries in the world are committed to several trillion Hz converter utility.the principle of IntroductionThe switching power supply of the process is quite easy to understand, linear power supplies, power transistors operating in the linear mode and linear power, the PWM switching power supply to the power transistor turns on and off state, in both states, on the power transistor V - security product is very small (conduction, low voltage, large current; shutdown, voltage, current) V oltammetric product / power device is power semiconductor devices on the loss.Compared with the linear power supply, the PWM switching power supply more efficient process is achieved by "chopping", that is cut into the amplitude of the input DC voltage equal to the input voltage amplitude of the pulse voltage. The pulse duty cycle is adjusted by the switching power supply controller. Once the input voltage is cut into the AC square wave, its amplitude through the transformer to raise or lower. Number of groups of output voltage can be increased by increasing the number of primary and secondary windings of the transformer. After the last AC waveform after the rectifier filter the DC output voltage.The main purpose of the controller is to maintain the stability of the output voltage, the course of their work is very similar to the linear form of the controller. That is the function blocks of the controller, the voltage reference and error amplifier can be designed the same as the linear regulator. Their difference lies in the error amplifier output (error voltage) in the drive before the power tube to go through a voltage / pulse-width conversion unit.Switching power supply There are two main ways of working: Forward transformand boost transformation. Although they are all part of the layout difference is small, but the course of their work vary greatly, have advantages in specific applications.the circuit schematicThe so-called switching power supply, as the name implies, is a door, a door power through a closed power to stop by, then what is the door, the switching power supply using SCR, some switch, these two component performance is similar, are relying on the base switch control pole (SCR), coupled with the pulse signal to complete the on and off, the pulse signal is half attentive to control the pole voltage increases, the switch or transistor conduction, the filter output voltage of 300V, 220V rectifier conduction, transmitted through the switching transformer secondary through the transformer to the voltage increase or decrease for each circuit work. Oscillation pulse of negative semi-attentive to the power regulator, base, or SCR control voltage lower than the original set voltage power regulator cut-off, 300V power is off, switch the transformer secondary no voltage, then each circuit The required operating voltage, depends on this secondary road rectifier filter capacitor discharge to maintain. Repeat the process until the next pulse cycle is a half weeks when the signal arrival. This switch transformer is called the high-frequency transformer, because the operating frequency is higher than the 50HZ low frequency. Then promote the pulse of the switch or SCR, which requires the oscillator circuit, we know, the transistor has a characteristic, is the base-emitter voltage is 0.65-0.7V is the zoom state, 0.7V These are the saturated hydraulic conductivity state-0.1V-0.3V in the oscillatory state, then the operating point after a good tune, to rely on the deep negative feedback to generate a negative pressure, so that the oscillating tube onset, the frequency of the oscillating tube capacitor charging and discharging of the length of time from the base to determine the oscillation frequency of the output pulse amplitude, and vice versa on the small, which determines the size of the output voltage of the power regulator. Transformer secondary output voltage regulator, usually switching transformer, single around a set of coils, the voltage at its upper end, as the reference voltage after the rectifier filter, then through the optocoupler, this benchmark voltage return to the base of the oscillating tube pole to adjust the level of the oscillation frequency, if the transformer secondary voltage is increased, the sampling coil output voltage increases, the positive feedback voltage obtained through the optocoupler is also increased, this voltage is applied oscillating tube base, so that oscillation frequency is reduced, played a stable secondary output voltage stability, too small do not have to go into detail, nor it is necessary to understand the fine, such a high-power voltage transformer by switching transmission, separated and after the class returned by sampling the voltage from the opto-coupler pass separated after class, so before the mains voltage, and after the classseparation, which is called cold plate, it is safe, transformers before power is independent, which is called switching power supply.the DC / DC conversionDC / DC converter is a fixed DC voltage transformation into a variable DC voltage, also known as the DC chopper. There are two ways of working chopper, one Ts constant pulse width modulation mode, change the ton (General), the second is the frequency modulation, the same ton to change the Ts, (easy to produce interference). Circuit by the following categories:Buck circuit - the step-down chopper, the average output voltage U0 is less than the input voltage Ui, the same polarity.Boost Circuit - step-up chopper, the average output voltage switching power supply schematic U0 is greater than the input voltage Ui, the same polarity.Buck-Boost circuit - buck or boost chopper, the output average voltage U0 is greater than or less than the input voltage Ui, the opposite polarity, the inductance transmission.Cuk circuit - a buck or boost chopper, the output average voltage U0 is greater than or less than the input voltage Ui, the opposite polarity, capacitance transmission.The above-mentioned non-isolated circuit, the isolation circuit forward circuits, feedback circuit, the half-bridge circuit, the full bridge circuit, push-pull circuit. Today's soft-switching technology makes a qualitative leap in the DC / DC the U.S. VICOR company design and manufacture a variety of ECI soft-switching DC / DC converter, the maximum output power 300W, 600W, 800W, etc., the corresponding power density (6.2 , 10,17) W/cm3 efficiency (80-90)%. A the Japanese Nemic Lambda latest using soft-switching technology, high frequency switching power supply module RM Series, its switching frequency (200 to 300) kHz, power density has reached 27W/cm3 with synchronous rectifier (MOSFETs instead of Schottky diodes ), so that the whole circuit efficiency by up to 90%.AC / DC conversionAC / DC conversion will transform AC to DC, the power flow can be bi-directional power flow by the power flow to load known as the "rectification", referred to as "active inverter power flow returned by the load power. AC / DC converter input 50/60Hz AC due must be rectified, filtered, so the volume is relatively large filter capacitor is essential, while experiencing safety standards (such as UL, CCEE, etc.) and EMC Directive restrictions (such as IEC, FCC, CSA) in the AC input side must be added to the EMC filter and use meets the safety standards of the components, thus limiting the miniaturization of the volume of AC / DC power, In addition, due to internal frequency, high voltage, current switching, making the problem difficult to solve EMC also high demands on the internal high-density mountingcircuit design, for the same reason, the high voltage, high current switch makes power supply loss increases, limiting the AC / DC converter modular process, and therefore must be used to power system optimal design method to make it work efficiency to reach a certain level of satisfaction.AC / DC conversion circuit wiring can be divided into half-wave circuit, full-wave circuit. Press the power phase can be divided into single-phase three-phase, multiphase. Can be divided into a quadrant, two quadrant, three quadrants, four-quadrant circuit work quadrant.he selection of the switching power supplySwitching power supply input on the anti-jamming performance, compared to its circuit structure characteristics (multi-level series), the input disturbances, such as surge voltage is difficult to pass on the stability of the output voltage of the technical indicators and linear power have greater advantages, the output voltage stability up to (0.5)%. Switching power supply module as an integrated power electronic devices should be selected。
毕业设计英文翻译
沈阳工业大学化工装备学院毕业设计(论文)外文翻译毕业设计(论文)题目:含硫氨污水冷却器外文题目:Head processing technology译文题目:封头加工工艺院(系):化工装备学院专业班级:过控0802班学生姓名:孙鹏博指导教师:闫小波2012年3月11日Head processing technology1.welding process1.1welding operationOur factory common welding methods are: manual welding, argon arc welding, submerged arc welding.(1) manual welding is mainly used for carbon steel 3-6mm plate welding.(2) submerged arc welding to more than 8mm carbon steel stainless steel sheet welding mainly.(3)3-6mm stainless steel argon arc welding with welding mainly. Commonly used stainless steel wire ER304and ER316L steel wire, commonly used to J422and J507and J426and J427low-temperature welding consumables. Flux of carbon steel used is the HJ431, stainless steel commonly used is HJ260,.As a result of welding wire flux can be easily affected with damp, stored in the infrared drying machine, flux HJ431and HJ260drying temperature is 250-300℃. Welding wire J422and J350drying temperature were 150℃ and 300 ℃Welding process is completely in accordance with the" welding" execution, sheet thickness determines the welding to welding or double sided arc welding in welding, after the weld seam inspection ( RT X ray ) judgment without pores, cracks and other defects, such as found in the above deficiencies, to the repair, until the filming.1.2 welding operation standard(1) welding procedure card after receiving process, affirm the process card and physical material, quantity, unit number, specifications, size instruction number is consistent, whether there is debris around the wafer, wafer splashes whether clean removal, such as treatment is not clean, will use the grinding clean.(2) there is no welding test plate, groove cutting quality can meet the requirement, material surface without obvious defects, such as abnormal response.(3) according to the" Regulations" welding procedure card check of welding groove type and dimensions correspond to.(4) on each side of groove surface grinding, butt edge offset is not greater than the10% thickness, and not more than1.5mm.(5) point fixed the first weld layer terminal welding length not less than 50mm, arc board specifications should be 150*150mm and a mask having R arc, team rounds should be given within 8 hours of welding, or to use flame to the moisture inside the baking groove.(6) the welder holds" welding" and" welding records" for welding consumables, welding two class library for registration, using flux field volume should not exceed 4 hours, or to continue to back into the oven drying.(7) a, preheating plate thickness not less than 30mm carbon steel, low alloy steel, the preheating temperature of welding process by" card"," standard" provisions of the welding technology.B, preheating range width not less than 4mm and no less than 100mm. C, in the process of welding groove at any time temperature shall not be less than the prescribed temperature.D, when welding temperature is below 0 ℃( arbitrary thickness) must be heated to 15 ℃or above in order to welding.(8) a before welding, welding to welding equipment inspection, examination was normal before welding facilities.According to B,"" the requirements of welding process welding, welding and fill in the recordsC, welding, welding layers shall be in accordance with" welding" requirements, welding shall not be a large current, less layers. (9) removal of the root a, stainless steel cleaning before the root groove sides, within the range of 300mm, splashing paint coating.B, using carbon arc air gouging, should be selected according to the request carbon rod diameter.C, root cleaning, grinding cleaning groove and two side the existence of carburized layer, oxide, slag and other sundries. Grinding width: manual welding, rust, oxide above 20mm, oil30mm above, automatic welding, rust, grease, oxides 25mm50mm groove inner grinding requirements, carbon steel, low alloy steelδn ≤10mm weld, its two ends within the range of 300mm carburized layer must be completely removed, the rest part allows the removal of more than 50%. Other non-ferrous metals must be completely clear. [3]D, root cleaning, composite steel Cr-Mo, manual welding and the thicknessofδn ≥30mm welds shall be examined by PT.(10) during the process of welding defect repair by welding repair welding repair monitor instruction experienced welders as. Repair welding process should eliminate soldering phenomenon, or polished after welding, the following defects must be removed before welding to welding crack,①partial②③pits the stomaA shall not be lower than the parent material, weld.B, there shall be no undercutting.C, without removing the residual high seam. The surface shall not have cracks, pores, crater, undercut and slag inclusions, and may not retain the slag and spatter.D, removal of residual high weld inspection shall not have any defect display PT.E, such as the defects of carbon steel, low-alloy steel repair procedures: a grinding wheel or a carbon arc gouging polishing cleaning→ PT check grinder grinding out the welding groove, welding, PT, stainless steel repair procedures: a grinding wheel or a carbon arc gouging polishing cleaning→PT (δ n≥ 2mm need )→grinder polished to a welding groove welding→ PT examination. [4](12) welded internal rework, repair procedures: location of defect, defect removal→ PT→→removal check welding weld→ PT examination. [5] (13) according to RT film, RT staff and the welders in welding seam together determine the location of defects, including the following requirements when using UT to determine the defect position, the first repairδ n≥ 30mm use UT to determine the location of defects, two or three repairδ n≥ 20mm using UT to determine the defect position, UT positioning by RT after class. The position and depth of defect ( calibration side shall be the depth of defect≤1/2 side).(14) after the welding inspector or monitor by confirmed, in the process card signed your name and object together with transfer to the next process, by the next process responsibility recognition can.2.stamping process2.1stamping operationStamping operation is small head forming an important operation. The same stamping is also head of the cracking, thinning appeared most processsection.2.2punching machine.(1) the master cylinder is mainly used to connect the die head, is the head forming the necessary parts.(2) side cylinder used for pressing die ring, fixing the upper and lower mold ring of head disk. The head in the pressing process is to prevent the crease, as an important part of the drum kit.(3) the overflow valve used for controlling the compressor overall pressure, prevent the wafer during the pressing process of tears. (4) stamping valve in pressure, stamping valve on pressure relief, achieve average pressure effect.In addition, circuit boards, motors, circuit boards, storage tank, operation platform, pedestal are stamping machine components.2.3.3 stamping operation steps(1) first of all to undertake a blanking process card, find a good wafer.(2) the control process card on the technological requirements, put ona set of corresponding die, and with the use of gauges to determine the selected die size and to suppress the wafer size.(3) the wafer is clamped on the upper and lower mold inside the circle, and determine the die head of the center point and the center point of the wafer in a straight line.(4) the operation ring mold and die relative motion, pressure test, according to the control rod rebound to judge the size of the pressure, thereby regulating pressure size.(5) pressure test end, pressed wafer, stamping.2.3the stamping operation standard(1) the control task orders, confirm physical and process card is consistent, according to the process card confirming workpiece number, material, specification, batch number and other factors, at the same time check wafer end there is no crack, burr, polished wafer whether it meets the requirements, whether chamfer, is facing the good, there are special requirements when the problem is found, in time to contact.(2) according to the process card correct selection of die mold surface, inspection, found bruises and serious injury must be polished, but must be clean mold surface corrosion and dirt.(3) according to the technology card size, shape, texture, straight edge higher to suppress.(4) the warm-stamping ( according to requirement sheet property is heated to a certain temperature, and then stamping process ), to prepare a baking gun, gas, oxygen, percussion with head shall prepare the corresponding template, double-sided film to the wafer edge of both sides in a range of about 200-300mm template removal, and clear the film surface. [6] (5) mounted on the lower die, as the case to join the die pad, the wafer inside and outside surface coated with oil, applied range of top to200-300mm, smear should be uniform, the upper and lower mold are evenly coated.(6) the first gold stamping head, hanging out with a model head, check section shape, at the same time, check whether the drum kit, and there is no thinning, and check the surface has no scratch, hoop printing, such as none of the above abnormalities can continue to stamping, head forming, sealing surfaces such as scratches are timely grinding, and confirm the minimum board thickness, confirm whether a scratch, strain, curved peel, orange peel, drum kits, wrinkle, hoop printing etc..(7) such as a head drum kit fold phenomenon should be together with the card with the move to rework process technology.(8) each head should be able to see the instruction, piece number, material, or to transplantation, each product specifications after testing, the process card ( to sign the name ) together to the next process, by the next process validation.3.pressure drum process3.1pressure drum operationPressure drum process and stamping processes are the same steps in the process, stamping process range of φ 159- φ1900mm and pressure drum process is in the range of φ 1600- φ4800mm. And stamping is different pressure drum mostly the head generally forming, eventually forming is completed by spinning, stamping without the special requirements of customers, eventually forming step is not required. φ 1600- φ1900mm heads the two processes is needed.3.2pressure drum machine.(1) the main cylinder is provided with an upper die head is pressed drumexecution as long as part of.(2) supporting seat fixed lower die and upper die head center in a straight line.(3) supporting frame1is provided with a rolling wheel, a position adjusting before and after.(4) supporting frame is provided with a rolling wheel rotating disk II. In addition, there are hydraulic system, the motor, oil pump, oil tank, and a control console.3.3pressure drum machine operation steps(1) first of all to undertake a blanking process card, find a good wafer.(2) the control process card on the technological requirements, put ona set of corresponding die, and with the use of gauges to determine the selected die size and to suppress the wafer size.(3) and stamping machine is different from the original film is not pressure drum center began to suppress, but from the wafer edge, as long as the die and wafer alignment on the line.(4) the pressing process is continuously by controlling the rotation wheel is driven by the rotation of a wafer rotating, according to a certain order to suppress.(5) in after the pressing process, prepared template matching. If a deviation to make further adjustments.3.4pressure drum operation standard(1) die on the quality of the products and the smooth pressure drum forming crucial. Therefore, require that the operator must according to the processing situation of choice for mold and timely adjust shim plate.(2) the operator receives the process card, see process card, according to the process card check objects, to confirm the real instruction, one-piece, material. Number, batch number etc.. According to the choice of mold process card.(3) for EHA, EHB head shapes have adopted the 0.82*D standard selection, for DHB, PSH, MD and other special products according to technology card selection of mold, but in principle according to P*0.82/1.15or P*0.82/1.2 standard selection. [1](4) pressing carefully before inspection wafer quality, no seam wafer end is smooth, there is no gap, surface has no cutting slag and defects.(5) a weld in addition to carefully check the end of the wafer wafer defects, at the same time should be checked for weld seam is higher than that of base metal, weld ends of are welding spatter, weld end grinding smooth, there is no crack notch.(6) two or two or more superimposed when pressed, each slice of the joint surface should be clean, according to the circumstances must entrust welding class, the wafer is welded together to suppress.(7) detection of wafer thickness ( the thickest, most thin, whether and process card, measurement of wafer size and process card.(8) suppression must be removed before the inside and outside surface of all debris, to prevent pitting appeared.(9) for general stainless steel materials ( more than 5mm plate ) using Teflon plate mold and the lower mold dressing on surface polished smooth ( necessary nowadays mold to Teflon plate. ) to ensure the surface quality of the workpiece, while in the process of the pressing need to avoid debris into molds and semi-finished products. [6](10) the pressing process, when the wafer is a R shape, must use the corresponding R model measurement, the pressing process should be considered to adjust the pressure deformation degree.(11) pressing is finished, the measurement of plate thickness, measuring arc length. Check surface quality, check end and weld end is smooth ( necessary to polish out the ceremony ).(12) to check the semi-finished product with process card is on the move to the next process ( and sign the name ) by the next process to confirm acceptance before.4.spinning process4.1spinning operationThe spinning process is pressed after the drum head molding process, mainly for large head R and straight edge formation.4.2spinning machine.(1) forming wheel is connected to the corresponding mold, forming in the head inside, mold top with half formed head R and straight edge is tangent to tangent.(2) supporting wheel is also connected and molded wheel mold, forming in the head outside, and a forming wheel tangent.(3) base for fixing head, and the bottom according to head size before and after moving, the head should be installed so that the center of the base and the head of the center in a straight line.(4) the center rod is used for fixing head, and the center and the center of the base is in a straight line.In addition to the motor, a circuit board, is connected to the shaft, anda control console.4.3spinning procedure(1) to undertake pressure drum process card, according to the card to determine the corresponding head spinning.(2) according to the head of the diameter, select the corresponding upper and lower mold.(3) the clamping head, ensure that the head of the center point and the center of the base point in a straight line.(4) to adjust the molding wheel and the head of tangent, then according to the forming wheel position adjustment roller.(5) in the spinning process to observe the forming roller and the supporting roller relative position, and continue to use the template on the line alignment. Until the R reaches the requirements.4.4spinning operation standard(1) spinning wheel material for steel bearings or ductile iron, mold on the quality of the products and can spin forming closely related, therefore the operator must be processed according to choose suitable mold, at the same time, because of the shape of the mold and the surface condition of the quality of the workpiece has a great influence, therefore, before processing and machining process must on the mold for full inspection.(2) according to the process card requirements, confirm wafer, pressure drum or preload semi-finished instruction number, specifications, quantity of material, compliance, and check the quality of surface and end with no defect, abnormal timely and on the procedures of contact, and in a timely manner(3) check the semi-finished end is smooth, with or without notch, crack, surface has no cutting or welding slag, and shall inspect the weld seam is higher than that of base metal, weld ends whether spatter, weld end grinding smooth, there is no crack. [7](4) pressure drum or to the press after the finished product, must checkfor folding, cracking, crack is not conducive to the spinning processing defects.(5) for stainless steel workpiece, through to the pickling method of decontamination.(6) according to the process card selection of mold, general small arc r size requirements as a basis for selecting the internal wheel. (7) according to the different material, thickness of plate and sheet rebound, selection is slightly smaller than the internal wheel circular arc R.(8) for the special requirements of the product, according to its shape design inside the wheel, confirm the mold surface, good polishing processing.(9) spinning processing, in order to prevent scratching and improve the processing performance, suitable lubricant ( grease ) to prevent process heating head appears on the surface of hot cracks and scratches, can also prolong the service life of die.(10) the spinning process, should be considered a workpiece shaping and timely for pressure adjustment.(11) after the molding process, deal with the size, shape, thickness, surface quality inspections, confirmation.(12) molded product with the card with the transfer process to the next process ( in the process card signed their name ) by the procedures under the inspector or monitor check before.5.groove processThe 5.1groove Essentials(1) groove process is a head of the data ( including circumference, total height) to achieve JB/T4746 standard key process. [1](2) groove is in order and cylinder head connection time, make welding more thoroughly.(3) the main groove cutting process and cutting process tools, is the use of plasma cutting.(4) cutting, according to the card on the technological requirements, determine groove type ( inner groove, outside the mouth, X groove ) and determine the groove angle.(5) the groove before the head splashing agent applicator.(6) groove when the first test slope, then a protractor measuring angle, identified in the tolerance range, after adjustment, the whole slope. The 5.2groove operation standard(1) according to the process card to find real, order confirmation No., specification, material, batch number, quantity and check whether the workpiece has a drum kit, crack, delamination, wrinkle, and whether the loss of a round, found problems in a timely manner to contact, processing, the plate thickness of more than 8mm, is suggested to lose the round groove, the following 6mm, tooling plate pressure is groove.(2) stainless steel head, should be in the groove wall smearing splash front head agent, prevent groove, slag spout to head on the wall. (3) head onto the beveling machine before, first confirm the head weight, based on the weight of suitable sling, sling safety inspection.(4) head onto the groove machine, beveling rotary table adjustment screw rod, with a center adjusting position, rotating table, is aligned to the center.(5) groove, according to technology card height and height tolerance groove height ruler to draw lines, confirm the high line, the slope slope, should first slope flat groove, and then the slope groove.(6) outside the mouth or the inner groove angle should be controlled within ± 2.5 tolerance.(7) groove after, should check the head circumference, height, straight edge, angle, if not qualified to repair process, repair.(8) qualified head will remove and clean the slag grinding head internal slag, together with card transfer to the next process ( and sign their name ) by the next process inspector confirmation can be.6.polishing process6.1 polishing process steps(1) according to the card process requirements, identify the need for polishing head.(2) the head rotating table, determine the level of, the clamping head.(3) polishing from edge to center, or from the center to the edge; according to the diameter size determine the head beam, lower speed and working stage, after moving speed.(4) check the polishing condition, appropriate for rework.The 6.2polishing operation standard(1) according to the process card and materials to confirm the product instruction number, specifications, material, batch number, quantity, and check whether the workpiece has a drum kit, crack, delamination defects, and whether the loss of a round, found problems in a timely manner to contact, processing, check the appearance, to determine the need for manual processing, the polishing before hook head to mark.(2) according to the requirements of the choice of using a polishing, polishing pads, and the necessary auxiliary tool.(3) confirm the head weight, based on the weight of suitable sling, and check whether the safety hanger.(4) the head hanging onto a work table, adjust the center, at the same time to ensure that the head is in the basic level (0-5 deviations ).(5) people in the scene when polishing polishing, attention, especially the left centre, speed fast, or outward from a center left, a little pressure to increase, from the edge to the center of pressure during polishing, to a little decrease in polishing head, thin wall, as the case may be mounted shockproof wheel, at the same time attention to mechanical work has no abnormal.(6) after the completion of inspection head polishing, with or without defect, and the necessary contact.(7) the Polish well head with coated packaging, in the process card signed their names, together with the head and process the card with the circulation storage, and by the next inspection approval.封头加工工艺1.焊接工序1.1 焊接操作我们厂常用的焊接方法有:手工焊、氩弧焊、埋弧焊。
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本科生毕业设计(论文)外文科技文献译文译文题目(外文题目)学院(系)Socket网络编程的设计与实现A Design andImplementation of Active Network Socket Programming机械与能源工程学院专学业号机械设计制造及其自动化071895学生姓名李杰林日期2012年5月27日指导教师签名日期摘要:编程节点和活跃网络的概念将可编程性引入到通信网络中,并且代码和数据可以在发送过程中进行修改。
最近,多个研究小组已经设计和实现了自己的设计平台。
每个设计都有其自己的优点和缺点,但是在不同平台之间都存在着互操作性问题。
因此,我们引入一个类似网络socket编程的概念。
我们建立一组针对应用程序进行编程的简单接口,这组被称为活跃网络Socket编程(ANSP)的接口,将在所有执行环境下工作。
因此,ANSP 提供一个类似于“一次性编写,无限制运行”的开放编程模型,它可以工作在所有的可执行环境下。
它解决了活跃网络中的异构性,当应用程序需要访问异构网络内的所有地区,在临界点部署特殊服务或监视整个网络的性能时显得相当重要。
我们的方案是在现有的环境中,所有应用程序可以很容易地安装上一个薄薄的透明层而不是引入一个新的平台。
关键词:活跃网络;应用程序编程接口;活跃网络socket编程1 导言1990年,为了在互联网上引入新的网络协议,克拉克和藤农豪斯[1]提出了一种新的设计框架。
自公布这一标志性文件,活跃网络设计框架[2,3,10]已经慢慢在20世纪90 年代末成形。
活跃网络允许程序代码和数据可以同时在互联网上提供积极的网络范式,此外,他们可以在传送到目的地的过程中得到执行和修改。
ABone作为一个全球性的骨干网络,开始进行活跃网络实验。
除执行平台的不成熟,商业上活跃网络在互联网上的部署也成为主要障碍。
例如,一个供应商可能不乐意让网络路由器运行一些可能影响其预期路由性能的未知程序,。
因此,作为替代提出了允许活跃网络在互联网上运作的概念,如欧洲研究课题组提出的应用层活跃网络(ALAN)项目[4]。
在ALAN项目中,活跃服务器系统位于网络的不同地址,并且这些应用程序都可以运行在活跃系统的网络应用层上。
另一个潜在的方法是网络服务提供商提供更优质的活跃网络服务类。
这个服务类应该提供最优质的服务质量(QOS),并允许路由器对计算机的访问。
通过这种方法,网络服务提供商可以创建一个新的收入来源。
对活跃网络的研究已取得稳步进展。
由于活跃网络在互联网上推出了可编程性,相应地应建立供应用程序工作的可执行平台。
这些操作系统平台执行环境(EES),其中一些已被创建,例如,活跃信号协议(ASP)[12]和活跃网络传输系统(ANTS)[11]。
因此,不同的应用程序可以实现对活跃网络概念的测试。
在这些EES 环境下,已经开展了一系列验证活跃网络概念的实验,例如,移动网络[5],网页代理[6],多播路由器[7]。
活跃网络引进了很多在网络上兼有灵活性和可扩展性的方案。
几个研究小组已经提出了各种可通过路由器进行网络计算的可执行环境。
他们的成果和现有基础设施的潜在好处正在被评估[8,9]。
不幸的是,他们很少关心互操作性问题,活跃网络由多个执行环境组成,例如,在ABone 中存在三个EES,专为一个EES编写的应用程序不能在其他平台上运行。
这就出现了一种资源划分为不同运行环境的问题。
此外,总是有一些关键的网络应用需要跨环境运行,如信息收集和关键点部署监测网络的服务。
在本文中,被称为活跃网络Socket编程(ANSP)的框架模型,可以在所有EES下运行。
它提供了以下主要目标:♦♦通过单一编程接口编写应用程序。
由于ANSP提供的编程接口,使得EES的设计与ANSP 独立。
这使得未来执行环境的发展和提高更加透明。
♦♦ANSP 针对不同执行环境之间的互操作性问题。
通过的ANSP设计,不同EES的优点和缺点显而易见。
这将有助于在将来设计更好的EES。
ANSP 的主要目标是使在ANSP 下编写的所有应用程序,可以运行在ABone测试平台。
而ANSP框架在统一网络环境下是必不可少的,我们相信,在不同环境下的通用性,对未来执行环境的发展是有利的。
ANSP并不是取代所有现有的环境,而是研究启用新的网络服务执行环境。
因此,ANSP 设计是对所有执行环境安装薄而透明的应用层。
目前,它的代码自动加载依赖于底层环境。
因此,部署在路由器的ANSP是可选的,不需要任何执行环境的变化。
2 针对ANSP的设计问题ANSP 统一现有各EES的编程接口。
ANSP 设计在概念上类似于中间件的设计,为不同的EES提供适当的翻译机制。
一个统一的接口只是整个ANSP平台的一部分。
有很多需要考虑的问题,除了翻译一套编程接口,在不同EES下可执行文件调用,也包括其他的设计问题,例如,♦♦♦♦♦统一的线程库处理线程操作。
全球性软件存储,可以在给定的路由器上进行不同环境下的信息共享。
统一的解决方案用于不同的环境,更重要的是,路由信息交换机制应横跨EES获得全球统一的网络视图。
应该是独立于任何活跃网络编程语言的编程模型。
最后,翻译机制要隐藏头结构的异构性。
A. 异构性编程模型在程序调用时,每个执行环境提供各种抽象的服务和资源。
一套组件模型每个部分都有其自己的编程接口。
抽象的封装编程模型[10]是在活跃网络中最流行的设计,这种模型在ANTS[11] 和ASP[12]使用,并正被ABone支持。
虽然他们是在相同的封装模型基础上开发的,但各自的组件和接口是不同的。
因此,在一个EES 上的程序不能运行在其他EES 上。
ANTS和ASP的编程模型如图1 所示。
ANTS包括三个不同的组件:应用程序,封装,和执行环境。
存在针对唯一来源和目的地路由器的应用程序用户接口。
然后,用户可以指定其定制的网络行为。
根据程序的功能,应用程序发送一个或多个封装进行操作。
这两个应用程序和封装工作的执行环境,为其内部的编程资源提供输出接口。
每次访问路由器时封装便执行其操作。
当它到达目的地,在目的地的应用程序就会以封装进行回复或提示用户事件已经收到。
ANTS 的一个缺点是,它仅允许“引导”应用程序访问。
图1 ANTS和ASP的编程模型相比之下,ASP不限制用户运行“引导”应用程序。
其程序接口与ANTS不同,但ASP 也由三个组成部分:客户端应用程序,环境和AA组件。
应用程序客户端可以在活跃或不活跃的主机上运行。
它可以通过简单的请求消息发送到EES来激活应用程序。
客户允许其用户在附近的活跃路由器触发操作。
AA组件是网络服务的核心,其规格分为两部分。
其中一部分指定其来源和目的地路由器的行动,其作用类似于ANTS中的应用,但它不提供与用户交互的直接接口。
另一部分定义了它在内部网络中的行为,与ANTS 中封装的功能行为相似。
为了解决这两种模式的异构性,ANSP需要引进一套新的编程接口,它的接口和执行模型映射到内部路由器的EES。
B. 统一线程库为了各个实例之间不互相影响和访问其他信息,可执行环境必须保证各个实例间的独立性。
有多种方法来执行访问控制。
一个简单的方法是为实例应用程序配备一个虚拟机。
这依赖于虚拟机隔离服务的安全设计。
ANTS 就是采用这种方法的一个例子。
然而,使用多个虚拟机需要的资源量相对较大,并可能在某些情况下,效率低下。
因此,某些环境,如ASP,允许网络服务在虚拟机上运行,但只允许其有限地访问自己的包库。
例如,ASP提供强制访问控制的线程库。
针对这些线程访问机制的差异,ANSP提供允许不同线程机制统一访问的新线程库。
C. 软存储软存储允许封装在路由器上插入和检索信息,从而使多个封装能够交换网络内的信息。
然而,网络服务在不同的路由器环境下执行时容易发生问题,尤其是当网络服务在一个环境中插入信息,稍后在相同路由器但是不同环境下检索数据时这个问题尤其严重。
由于执行环境不允许交换信息,网络服务无法检索其以前的数据。
因此,我们的ANSP 框架需要考虑到这个问题,并提供在每个路由器上进行数据访问的软存储机制。
D.统一网络的完整视图当用ANSP编写应用程序时,它便可以在不同环境下完美运行。
以前基于不同EES的小型分区网络可以合并成为一个大的网络,整个大网络的拓扑结构也就显得很有必要。
然而,不同的执行环境有不同的解决方案和专有的路由协议。
为了合并这些分区,ANSP 必须提供一个新的统一的解决方案。
这项新计划在任何环境下都能由ANSP编译出来。
定义了新的方案之后,新的路由协议可以实现在不同的环境之间交换拓扑信息。
这使得在各个网络环境中,其网络拓扑结构都有完整的视图。
E.独立语言模型任何编程语言都可以在可执行环境下编写,Java以动态代码承载能力使其成为最常用的语言之一。
实际上,ANTS 和ASP 都是用Java开发的。
然而,如图2 所示的活跃网络架构不限制使用其他语言开发执行环境。
例如,Abone中的anted 作为活跃网络后台进程提供路由器上多个执行环境的工作空间。
又如,PLAN 将在Abone上部署在OCaml中。
虽然现在的网络设计可以用任何语言在多个环境中进行编程,但是缺少使得应用程序在这些环境中完美运行的工具。
因此,ANSP 需要解决的问题之一就是设计一种可以使用不同编程语言的编程模型。
我们现在着重考虑ANTS和ASP 的设计,但PLAN 将是下一个待解决问题并提高ANSP的设计。
图2 ANSP框架模型F.封装头结构的异构性在不同的EES下头结构是不同的。
他们执行相关的信息,例如封装,封装的种类,来源和目的地。
当在目标环境中执行某些决定时这个信息是非常重要的。
一个统一的模式,应允许其程序代码在不同环境下执行。
然而,封装头阻止不同的环境来解析它的信息。
因此,ANSP应在目标环境收到这些信息之前进行相应头信息的转译。
3ANSP 编程模型下面我们将讨论提到过的ANSP设计中编程模型的问题。
这个建议框架提供了一套允许在所有执行环境下运行应用程序的统一的编程接口。
该框架如图3所示。
它是由两层活跃网络架构集成的,并且这两层都可以独立运作。
上层的应用程序提供一个统一的编程模型,下层的应用程序为在不同环境下的应用提供适当的转译过程。
这项服务很必要,因为每个环境都有其自己的头定义。
ANSP 提供了一套服务和资源的抽象编程调用。
以封装为基础的模型已用于ANSP并映射到ANTS和ASP 的模型中。
因此,ANSP 允许应用程序通过一系列单一接口访问不同环境下的编程资源。
映射必须以一致和透明的方式进行。
因此,ANSP好像是提供执行环境的应用程序,而实际上,它是一个能够使用底层所提供服务的重叠式结构。
ANSP 编程模型是基于四个组成部分之间的相互作用:客户端应用程序,应用程序存根,封装,服务器。