毕业设计说明书
英文文献及中文翻译
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专 指导教师：
2014 年 6 月
Introduction to Linux
1.1 History
1.1.1 UNIX
In order to understand the popularity of Linux, we need to travel back in time, ab out 30 years ago...
Imagine computers as big as houses, even stadiums. While the sizes of those com puters posed substantial problems, there was one thing that made this even worse: eve ry computer had a different operating system. Software was always customized to ser ve a specific purpose, and software for one given system didn't run on another system. Being able to work with one system didn't automatically mean that you could work w ith another. It was difficult, both for the users and the system administrators. Computers were extremely expensive then, and sacrifices had to be made even after th e original purchase just to get the users to understand how they worked. The total cost of IT was enormous.
Technologically the world was not quite that advanced, so they had to live with t he size for another decade. In 1969, a team of developers in the Bell Labs laboratories started working on a solution for the software problem, to address these compatibility issues. They developed a new operating system, which was
simple and elegant
written in the C programming language instead of in assembly code
able to recycle code.
The Bell Labs developers named their project "UNIX."
The code recycling features were very important. Until then, all commercially av ailable computer systems were written in a code specifically developed for one system . UNIX on the other hand needed only a small piece of that special code, which is now commonly named the kernel. This kernel is the only piece of code that needs to be ad apted for every specific system and forms the base of the UNIX system. The operating system and all other functions were built around this kernel and written in a higher pr ogramming language, C. This language was especially developed for creating the UNI
X system. Using this new technique, it was much easier to develop an operating syste m that could run on many different types of hardware.
The software vendors were quick to adapt, since they could sell ten times more s oftware almost effortlessly. Weird new situations came in existence: imagine for insta nce computers from different vendors communicating in the same network, or users w orking on different systems without the need for extra education to use another compu ter. UNIX did a great deal to help users become compatible with different systems.
Throughout the next couple of decades the development of UNIX continued. Mo re things became possible to do and more hardware and software vendors added suppo rt for UNIX to their products.
UNIX was initially found only in very large environments with mainframes and minicomputers (note that a PC is a "micro" computer). You had to work at a university , for the government or for large financial corporations in order to get your hands on a UNIX system.But smaller computers were being developed, and by the end of the 80' s, many people had home computers. By that time, there were several versions of UNI X available for the PC architecture, but none of them were truly free.
1.1.2 Current application of Linux systems
Today Linux has joined the desktop market. Linux developers concentrated on ne tworking and services in the beginning, and office applications have been the last barr ier to be taken down. We don't like to admit that Microsoft is ruling this market, so ple nty of alternatives have been started over the last couple of years to make Linux an ac ceptable choice as a workstation, providing an easy user interface and MS compatible office applications like word processors, spreadsheets, presentations and the like.
On the server side, Linux is well-known as a stable and reliable platform, providi ng database and trading services for companies like Amazon, the well-known online b ookshop, US Post Office, the German army and such. Especially Internet providers an d Internet service providers have grown fond of Linux as firewall, proxy- and web ser ver, and you will find a Linux box within reach of every UNIX system administrator
who appreciates a comfortable management station. Clusters of Linux machines are u sed in the creation of movies such as "Titanic" , "Shrek" and others. In post offices, th ey are the nerve centers that route mail and in large search engine, clusters are used to perform internet searches.These are only a few of the thousands of heavy-duty jobs th at Linux is performing day-to-day across the world.
It is also worth to note that modern Linux not only runs on workstations, mid- an d high-end servers, but also on "gadgets" like PDA's, mobiles, a shipload of embedde d applications and even on experimental wristwatches. This makes Linux the only ope rating system in the world covering such a wide range of hardware.
1.2 The user interface
1.2.1 Is Linux difficult?
Whether Linux is difficult to learn depends on the person you're asking. Experien ced UNIX users will say no, because Linux is an ideal operating system for power-use rs and programmers, because it has been and is being developed by such people. Everything a good programmer can wish for is available: compilers, libraries, develop ment and debugging tools. These packages come with every standard Linux distributi on. The C-compiler is included for free, all the documentation and manuals are there, and examples are often included to help you get started in no time. It feels like UNIX and switching between UNIX and Linux is a natural thing.
In the early days of Linux, being an expert was kind of required to start using the system. . It was common practice to tell a beginning user to "RTFM" (read the manua ls). While the manuals were on every system, it was difficult to find the documentatio n, and even if someone did, explanations were in such technical terms that the new us er became easily discouraged from learning the system.
The Linux-using community started to realize that if Linux was ever to be an imp ortant player on the operating system market, there had to be some serious changes in the accessibility of the system.
1.2.2 Linux for non-experienced users
Companies such as RedHat, SuSE and Mandrake have sprung up, providing pack aged Linux distributions suitable for mass consumption. They integrated a great deal o f graphical user interfaces (GUIs), developed by the community, in order to ease mana gement of programs and services. As a Linux user today you have all the means of get ting to know your system inside out, but it is no longer necessary to have that knowle dge in order to make the system comply to your requests.
Nowadays you can log in graphically and start all required applications without e ven having to type a single character, while you still have the ability to access the core of the system if needed. Because of its structure, Linux allows a user to grow into the system: it equally fits new and experienced users. New users are not forced to do diffi cult things, while experienced users are not forced to work in the same way they did w hen they first started learning Linux.
While development in the service area continues, great things are being done for desktop users, generally considered as the group least likely to know how a system wo rks. Developers of desktop applications are making incredible efforts to make the mos t beautiful desktops you've ever seen, or to make your Linux machine look just like yo ur former MS Windows or MacIntosh workstation. The latest developments also inclu de 3D acceleration support and support for USB devices, single-click updates of syste m and packages, and so on. Linux has these, and tries to present all available services in a logical form that ordinary people can understand.
1.3 Does Linux have a future?
1.3.1 Open Source
The idea behind Open Source software is rather simple: when programmers can r ead, distribute and change code, the code will mature. People can adapt it, fix it, debu g it, and they can do it at a speed that dwarfs the performance of software developers at conventional companies. This software will be more flexible and of a better quality than software that has been developed using the conventional channels, because more
people have tested it in more different conditions than the closed software developer e ver can.
The Open Source initiative started to make this clear to the commercial world, an d very slowly, commercial vendors are starting to see the point. While lots of academi cs and technical people have already been convinced for 20 years now that this is the way to go, commercial vendors needed applications like the Internet to make them rea lize they can profit from Open Source. Now Linux has grown past the stage where it was almost exclusively an academic system, useful only to a handful of people with a technical background. Now Linux provides more than the operating system: there is a n entire infrastructure supporting the chain of effort of creating an operating system, o f making and testing programs for it, of bringing everything to the users, of supplying maintenance, updates and support and customizations, etcetera. Today, Linux is ready to accept the challenge of a fast-changing world.
1.3.2 Ten years of experience at your service
While Linux is probably the most well-known Open Source initiative, there is an other project that contributed enormously to the popularity of the Linux operating syst em. This project is called SAMBA, and its achievement is the reverse engineering of t he Server Message Block (SMB)/Common Internet File System (CIFS) protocol used for file- and print-serving on PC-related machines, natively supported by MS Window s NT and OS/2, and Linux. Packages are now available for almost every system and p rovide interconnection solutions in mixed environments using MS Windows protocols : Windows-compatible (up to and including Win2K) file- and print-servers.
Maybe even more successful than the SAMBA project is the Apache HTTP serve r project. The server runs on UNIX, Windows NT and many other operating systems. Originally known as "A PAtCHy server" , based on existing code and a series of "patc h files" , the name for the matured code deserves to be connoted with the native Ameri can tribe of the Apache, well-known for their superior skills in warfare strategy and in exhaustible endurance. Apache has been shown to be substantially faster, more stable
and more feature-full than many other web servers. Apache is run on sites that get mill ions of visitors per day, and while no official support is provided by the developers, th e Apache user community provides answers to all your questions. Commercial suppor t is now being provided by a number of third parties.
In the category of office applications, a choice of MS Office suite clones is availa ble, ranging from partial to full implementations of the applications available on MS Windows workstations. These initiatives helped a great deal to make Linux acceptable for the desktop market, because the users don't need extra training to learn how to wo rk with new systems. With the desktop comes the praise of the common users, and not only their praise, but also their specific requirements, which are growing more intrica te and demanding by the day.
The Open Source community, consisting largely of people who have been contrib uting for over half a decade, assures Linux' position as an important player on the des ktop market as well as in general IT application. Paid employees and volunteers alike are working diligently so that Linux can maintain a position in the market. The more u sers, the more questions. The Open Source community makes sure answers keep comi ng, and watches the quality of the answers with a suspicious eye, resulting in ever mor e stability and accessibility.
1.4 Properties of Linux
1.4.1 Linux Pros
A lot of the advantages of Linux are a consequence of Linux' origins, deeply root ed in UNIX, except for the first advantage, of course:
Linux is free:
As in free beer, they say. If you want to spend absolutely nothing, you don't even have to pay the price of a CD. Linux can be downloaded for free from the internet.No registration fees, no costs per user, free updates, and freely available sourc e code in case you want to change the behavior of your system.
Most of all, Linux is free as in free speech:
The license commonly used is the GNU Public License (GPL). The license says t hat anybody who may want to do so, has the right to change Linux and eventually to r edistribute a changed version, on the one condition that the code is still available after redistribution. In practice, you are free to grab a kernel image, for instance to add sup port for teletransportation machines or time travel and sell your new code, as long as y our customers can still have a copy of that code. Linux is portable to any hardware pl atform: A vendor who wants to sell a new type of computer and who doesn't know w hat kind of OS his new machine will run (say the CPU in your car or washing machin e), can take a Linux kernel and make it work on his hardware, because documentation related to this activity is freely available. Linux was made to keep on running: As wit h UNIX, a Linux system expects to run without rebooting all the time. That is why a l ot of tasks are being executed at night or scheduled automatically for other calm mom ents, resulting in higher availability during busier periods and a more balanced use of t he hardware. This property allows for Linux to be applicable also in environments wh ere people don't have the time or the possibility to control their systems night and day. Linux is secure and versatile: The security model used in Linux is based on the UNI X idea of security, which is known to be robust and of proven quality. But Linux is no t only fit for use as a fort against enemy attacks from the Internet: it will adapt equally to other situations, utilizing the same high standards for security. Your development machine or control station will be as secure as your firewall. Linux is scalable: From a Palmtop with 2 MB of memory to a petabyte storage cluster with hundreds of nodes: add or remove the appropriate packages and Linux fits all. You don't need a supercom puter anymore, because you can use Linux to do big things using the building blocks provided with the system. If you want to do little things, such as making an operating system for an embedded processor or just recycling your old 486, Linux will do that a s well. The Linux OS and Linux applications have very short debug-times: Because Linux has been developed and tested by thousands of people, both errors and people t o fix them are found very quickly. It often happens that there are only a couple of hour s between discovery and fixing of a bug.
1.4.2 Linux Cons
There are far too many different distributions:
"Quot capites, tot rationes", as the Romans already said: the more people, the mo re opinions. At first glance, the amount of Linux distributions can be frightening, or ri diculous, depending on your point of view. But it also means that everyone will find w hat he or she needs. You don't need to be an expert to find a suitable release.
When asked, generally every Linux user will say that the best distribution is the s pecific version he is using. So which one should you choose? Don't worry too much a bout that: all releases contain more or less the same set of basic packages. On top of th e basics, special third party software is added making,or example, TurboLinux more s uitable for the small and medium enterprise, RedHat for servers and SuSE for worksta tions. However, the differences are likely to be very superficial. The best strategy is to test a couple of distributions; unfortunately not everybody has the time for this. Lucki ly, there is plenty of advice on the subject of choosing your Linux. One place is Linux Journal , which discusses hardware and support, among many other subjects. The Inst allation HOWTO also discusses choosing your distribution. Linux is not very user fri endly and confusing for beginners: In light of its popularity, considerable effort has b een made to make Linux even easier to use, especially for new users. More informatio n is being released daily, such as this guide, to help fill the gap for documentation avai lable to users at all levels. Is an Open Source product trustworthy?
How can something that is free also be reliable? Linux users have the choice whe ther to use Linux or not, which gives them an enormous advantage compared to users of proprietary software, who don't have that kind of freedom. After long periods of tes ting, most Linux users come to the conclusion that Linux is not only as good, but in m any cases better and faster that the traditional solutions. If Linux were not trustworthy, it would have been long gone, never knowing the popularity it has now, with millions of users. Now users can influence their systems and share their remarks with the com munity, so the system gets better and better every day. It is a project that is never finis
hed, that is true, but in an ever changing environment, Linux is also a project that cont inues to strive for perfection.
关于Linux的介绍
1.1 历史
1.1.1 UNIX
为了了解Linux的历史，我们需要追溯到30年前。想象一下像房子甚至体育馆一样大的计算机。除了电脑的体积带来的问题，有一件事情让这些变得更糟糕，那就是每个计算机都有一个不同的操作系统。软件定制服务一直是一个给定系统的特定目标，软件无法在另一个系统上运行。能够在一个系统下工作并不意味着也可以自动同另一个系统共事。这些无论对于用户还是系统管理员都是非常困难的。
由于计算机非常昂贵，所以人们不得不为之付出，即使购买计算机那也只是为了让用户了解他们是如何工作的。但是IT的总成本还是非常巨大的。
世界上的技术还没有那么先进，因此他们不得不和如此大的计算机共同再度过十年。在1969年，贝尔实验室的开发团队人员们开始研究，为解决软件问题，更好的完善兼容性。他们开发出一种新的操作系统，就是这个。简单巧妙用C语言设计代替汇编码能够循环利用的代码。
贝尔实验室开发的项目把它命名为“UNIX操作系统。”该代码循环的功能是非常重要的。在此之前，所有商用计算机系统是写在一个专门为系统开发的代码中。而UNIX只需要有一组特殊的代码，也就是现在俗称小片的内核。这个内核的代码是唯一的一块，需要为每一个特定的系统和各种形式的UNIX系统基础改编。操作系统和所有其他所有功能，都围绕这个核心，用更高级编程语言所编写的，C.这种语言是专为创造UNIX系统而发展的。使用这种新技术，更易于开发可以运行在不同类型硬件上的操作系统。
软件供应商们很快就意识到这一点，因为他们可以几乎毫不费力的售出超过原来软件十倍的销量。一个新奇的情况出现了：不同供应商生产的计算机可以连接到同一个网络，并且用户操作不同的操作系统无需再利用额外的时间去学习使用另一台计算机。UNIX帮助用户大大改善了不同系统兼容问题。
UNIX在未来持续几十年的不断发展中。更多的东西成为可能，并且硬件和软件的供应商们也增加了他们对UNIX产品的重视。
最初的UNIX，只为大背景环境下的大型机和小型机所使用（pc只是微型机）。如果你想使用UNIX, 那么你必须在大学、政府或者大型金融公司工作。
但是小的电脑也正在发展，80年代末，很多人家里都有电脑。在那个时候，有好几个版本的UNIX架构的PC可用，但其中没有一个是真正的开源。
1.1.2 Linux系统的应用现状
今天，Linux已经加入了台式机市场。 Linux开发人员集中在开始网络和服务环节，办公应用程序的最后障碍已经被拆除。我们不得不承认，微软已经占据了大部分市场，因此大量的人们开始选择替代品，在过去几年这种情况使Linux成为了一个可接受的工作站，它提供了一个简单的用户界面，文字处理软件兼容微软Office应用程序，试算表，简报等等。
在服务器端，Linux是众所周知的一个稳定和可靠的平台，像著名的网上书店亚马逊，美国邮政总局，德国军队和这些公司的数据库以及交易服务。特别是互联网服务提供商和互联网服务供应商已经开发出成熟的Linux防火墙，代理服务器和Web服务器，你会发现在每一个UNIX系统管理员都会赞赏管理站已经成为到一个舒适的工作平台。在电影创作中也使用了Linux集群机，如“泰坦尼克号”，“怪物史莱克”等。在邮局，他们是路由邮件和大型的搜索引擎的中枢系统，集群机还用来执行互联网搜索.这些只是在日日夜夜成千上万工作的linux中的一部分。还值得指出，现代的Linux不仅仅只在工作站上运行，还在中、高端服务器，也在像掌上电脑的，手机，船货的嵌入式应用，甚至对手表实验的“小玩意”上使用。这使Linux成为世界上唯一一个广泛应用的操作系统。
1.2 用户界面
1.2.1 Linux难吗？
Linux是否难学，取决于你问的人。有经验的UNIX用户会说不，因为Linux 是电力用户和程序员理想的操作系统，因为这些人已经使用并且正在开发它。
一个好的程序员都希望编译器，库，开发和调试工具是可用的。这些软件包来源于所有的标准Linux发行版。其中包括免费的C语言编译器，所有的文件和程序手册。并且举例内容也能帮助您在任何时间开始。感觉就像UNIX,并且可以在
UNIX和Linux之间自然的转换。在早期的Linux，成为一个专家需要从开始就使用它。这是一个普通的练习，用来告诉新的用户来“RTFM”（阅读手册）。虽然每个系统都有手册，但是找到文件仍然很难，即使有人做到了，解释了这样的技术术语，但是对于新用户的学习变得容易气馁。 Linux的使用社区开始意识到，如果Linux是以往任何时候成为操作系统市场上重要的成员，必须在该系统的亲和力上做大量的修改。
1.2.2 Linux的非经验的用户
如RedHat，SuSE和Mandrake的公司如雨后春笋般涌现，提供打包的Linux 发行版更适合大众消费。他们综合了大量的图形用户界面（GUI），由社区发展，以缓解方案和服务的管理。今天你作为一个Linux用户，你知道了你得到了系统的一切手段，但现在它不再有必要让用户了解这种知识，只为了使系统符合您的要求。
现在你可以登录图形和启动，甚至无需输入一个单一的字符，而你仍然有能力来访问该系统的核心。由于其结构，Linux允许用户发展系统：不论你是新手还是有经验的用户。当他们第一次开始学习Linux操作系统时，新用户不会被强迫做难度很大的事情，有经验的用户不会被迫以同样的方式工作。
而在服务方面的发展，对于桌面用户更好的事情已经发生。桌面应用程序的努力开发令人难以置信，使你见到你见过的最美丽的台式电脑，或使你的Linux 机器，就像你以前的MS Windows或Macintosh工作站。最新的发展情况也有3D 加速支持和USB设备支持，通过单击更新系统和数据包，等等。 Linux有这些，并试图开发所有人们所了解的并且在逻辑上可以实现的服务。
1.3 Linux是否有前途？
1.3.1 开放源码
开放源码软件背后的想法很简单：当程序员可以读取，分发和修改代码，代码将变得更成熟。人们能够适应它，解决它，调试时间，他们能够以软件开发公司同样的速度的处理他的性能。该软件将比曾经任何一个开发过的软件更加灵活，质量更好，因为相比于以往任何时候都在封闭的软件开发人员来说，能够
有更多的人有在不同测试条件下完善它。开放源码的开始对于商务的世界更轻的清晰，而且更慢。商业供应商也开始明白这一点。虽然许多学者和技术人员已经被说服了20年来，但现在仍然要走这条路。商业供应商像互联网应用一样，使他们意识到他们可以从开源获取利润。现在Linux已经度过了它的成长阶段，它几乎完全是一个学术体系，对于控制唯一有用的一点就是有技术背景。现在Linux提供的东西比操作系统更多：有一个完整的基础设施支持建立一个连锁的经营体系，并且制作和测试它，它能给用户带来一切方需要的，提供维修，更新和支持还有自定义，今天，Linux已经准备好接受一个迅速变化的世界的挑战。
1.3.2 十多年的经验为您服务
尽管Linux可能是最知名的倡议开放源码，但是还有另外一个项目，极大地促进了Linux操作系统的普及。这个项目被称为Samba，其成就是逆向工程的服务器消息块（SMB）/通用互联网文件系统（CIFS）协议用于文件和打印对本地的MS Windows NT支持的个人电脑相关设备，服务和OS / 2和Linux。现在一整套东西为几乎每个系统提供在混合环境中使用MS Windows协议互连解决方案：Windows兼容（直至并包括Win2K系统）文件和打印服务器。也许比Samba 项目更成功的是Apache HTTP服务器项目。该服务器运行在UNIX，Windows NT 和许多其他操作系统。原本被称为“一个修修补补的服务器”，“根据现有的代码和文件的一系列”补丁，这意味着成熟代码值得美国本土部落因其卓越的良好的Apache来命名，著名的战略和不竭耐力。 Apache已被证明是大幅度更快，更稳定，比许多其他Web服务器功能完整。 Apache是每天数百万游客的情况下运行，虽然没有官方的支持是由开发商提供的，但Apache用户社区提供您的所有问题的答案。现正由一些第三方提供商业支持。
在办公应用类，MS Office软件的选择是可用的，范围从局部到在MS Windows 工作站应用提供充分的实现。这些举措使Linux在桌面市场可以被大量人接受，因为用户并不需要额外的培训，学习如何使用新系统。随着台式电脑的共同用户的好评，不仅他们的一致好评，而且他们的具体要求，这是变得越来越复杂和日益苛刻。在开源社区，包括大量为社区做了5年以上贡献的人，保证Linux 的桌面上作为市场的重要参与者的地位，以及在一般资讯科技应用。带薪员工
和志愿者都正在努力使Linux可以保持在市场上的地位。越多的用户，更多的问题。开源社区可确保答案滚滚而来，用怀疑的目光观察答案的质量，会更具有稳定性和易用性。
1.4 Linux的性能
1.4.1 Linux的优点
Linux的很多优势是Linux的起源，深深扎根在UNIX中，当然除了第一个优势 Linux是免费的：他们说正如免费的啤酒，如果你想花钱买完全没什么，你甚至用不上支付一张CD的价钱。 Linux可以从互联网上免费下载。没有登记费，没有每用户成本，免费更新，如果你想改变你的系统，也会免费提供源代码给你。最重要的是，Linux和演讲一样是免费的：我们通常使用的许可证是GNU 公共许可证（GPL）。该许可规定，任何想做的人都有权改变Linux最后重新分配一个改变过的版本，最终有一个条件就是代码被改变以后仍然可用。在实践中，只要您的客户仍然可以拥有一组代码的副本。你可以自由地抓住例如一个内核映像，增加对teletransportation机器或时间旅行支持和销售的新的代码。 Linux 是可移植到任何硬件平台：一个愿意出售一种新型电脑的供应商，他们不知道新机器是将运行什么操作系统（例如，在您的汽车或洗衣机的CPU），可以采取一个Linux内核，使其在他的硬件工作，因为与此相关的活动文档是免费的。Linux 是持续运行：对于UNIX，Linux系统在运行中不希望总是重新启动。这就是为什么很多的任务会执行预定在晚上或其他平静的时刻的原因，在忙碌的时段造成较高的使用率和硬件的平衡。这个属性允许Linux在适用的环境中，人们也没有时间也没有可能去控制他们系统的昼夜。 Linux是安全的和通用的：在Linux中使用的安全模型是基于UNIX的安全观念，这是众所周知的强劲和公认的质量。但是Linux不仅适合作为从互联网对付敌人攻击的使用堡：它会同样适应于其他情况，利用同样高的安全标准。您的开发计算机或控制的电台会安全的成为你的防火墙。 Linux是可扩展性：从与 2 MB 存储器的一个掌上型电脑到 petabyte 储存有数以百计的波节的群集：添加或删除相应的软件包，Linux适合一切。你并不需要一台超级计算机了，因为你可以使用Linux做使用系统提供的建设做大事情。如果你想要做的小东西，比如制造用于嵌入式处理器的操作系统或者只是
回收的旧的486，Linux会做这点。在Linux操作系统和Linux应用程序有很短的调试时间：因为Linux已经很成熟，成千上万的人已经对其进行了测试，这些问题很快被人们定位并发现。发现一个bug并修复好只需要几个小时，是经常发生的事。
1.4.2 Linux的缺点
有太多的不同分布：
"Quot capites, tot rationes"，因为罗马人已经说过：人越多，越意见。乍看之下，Linux的发行量可能是恐怖的，或可笑的，这取决于您的观点。但是，这也意味着，每个人都会找到他或她需要什么。你不必成为一个专家，只需要找到一个合适的释放。
当记者问，一般每Linux用户会说，最好的分布是他在使用特定版本。所以，你应该选择哪一个？不要过分担心的是：所有版本包含或多或少的与基本包相同。论基础之上，特别是加入第三方软件制作，例如，TurboLinux的多为中小型企业，RedHat适合服务器，SuSE适合操作区但是，这些差异很可能是表面上的。最好的策略是测试成对的分布，可惜不是每个人都有这个时间。幸运的是，大量的意见对你的Linux选择的主题很有帮助。一个叫LinuxJournal的地方，其中讨论了硬件和支持对象还有其他话题。也会讨论你的安装分布。Linux不是友好的用户会让初学者困惑：因为他的流行，相当大的努力让Linux更容易使用，特别是新用户。较多的信息正在每日被释放，像是一个指南，为所有层次的用户填写文件编写的不足。是一个开源的产品值得信赖？
怎样才能使免费的东西也可以可靠呢？ Linux用户可以选择是否使用Linux，这给了他们巨大的优势，相对于私有软件的用户不会有这种自由。经过长时间的测试，大多数Linux用户得出的结论是，Linux是没有那么好而已，但在许多情况下比传统的解决方案更好，更快。如果Linux不可靠，那么他早就不会存在了，也不会有人知道它现在的普及与数百万用户了。现在，用户可以影响他们的系统并与社区分享他们的言论，因此系统每天都是越来越好。这是一个永远不会完成的项目，这是事实，但在一个不断变化的环境中，Linux是一个项目，也将继续精益求精。
企业成本控制外文翻译文献(文档含英文原文和中文翻译)
译文： 在价值链的成本控制下减少费用和获得更多的利润 摘要： 根据基于价值链的成本管理理念和基于价值的重要因素是必要的。首先，必须有足够的资源，必须创造了有利的价值投资，同时还需要基于客户价值活动链，以确定他们的成本管理优势的价值链。其次，消耗的资源必须尽量减少，使最小的运营成本价值链和确保成本优势是基于最大商业价值或利润，这是一种成本控制系统内部整个视图的创建和供应的具实践，它也是一种成本控制制度基于价值链，包括足够的控制和必要的资源投资价值的观点，创建和保持消费的资源到合理的水平，具有价值的观点主要对象的第一个因素是构造有利的价值链，从创造顾客价值开始；第二个因素是加强有利的价值链，从供应或生产客户价值开始。因此它是一个新型的理念，去探索成本控制从整个视图的创建和供应的商品更盈利企业获得可持续的竞争优势。 关键词：成本控制，价值链，收益，支出，收入，成本会计 1、介绍 根据价值链理论，企业的目的是创造最大的顾客价值；和企业的竞争优势在于尽可能提供尽可能多的价值给他们的客户，作为低成本可能的。这要求企业必须首先考虑他们是否能为顾客创造价值，和然后考虑在很长一段时间内如何创造它。然而，竞争一直以“商品”（或“产品”）作为最直接的载体，因此，传统的成本控制方法主要集中在对“产品”和生产流程的过程。很显然，这不能解决企业的问题，企业是否或如何能为客户创造价值。换句话说，这至少不能从根本上解决它。 因此，企业必须首先投入足够的资源，以便他们能够创建客户值取向，然后提供它以最少的资源费用。所以在整个视图中对价值创造和提供整体的观点来控制成本，它可以为客户提供完美的动力和操作运行机制运行成本的控制，也可以从根本上彻底克服了传统的成本控制方法的缺点，解决了无法控制的创造和供应不足的真正价值。基于此，本文试图从创作的整体观讨论成本控制提供价值并探讨实现良性循环的策略，也就是说，“创造价值投资成本供应价值创造价值”。 2、成本及其控制的基于价值链理念 2.1基于价值链的成本观念 根据价值链理论，如果企业是要被客户接受，它必须创造和提供能满足其客户的价值。因此，成本（价值或资源支付费用）这不离为创造和提供顾客价值的活动，其活动的价值链。因此，我们应该从价值链角度看成本的重要。
第二部分 控制理论 第1章 1.1控制系统的引入 人类控制自然力量的设计促进人类历史的发展,我们已经广泛的能利用这种量进行在人类本身力量之外的物理进程?在充满活力的20世纪中,控制系统工程的发展已经使得很多梦想成为了现实?控制系统工程队我们取得的成就贡献巨大?回首过去,控制系统工程主要的贡献在机器人,航天驾驶系统包括成功的实现航天器的软着陆,航空飞机自动驾驶与自动控制,船舶与潜水艇控制系统,水翼船?气垫船?高速铁路自动控制系统,现代铁路控制系统? 以上这些类型的控制控制系统和日常生活联系紧密,控制系统是一系列相关的原件在系统运行的基础上相互关联的构成的,此外控制系统存在无人状态下的运行,如飞机自控驾驶,汽车的巡航控制系统?对于控制系统,特别是工业控制系统,我们通常面对的是一系列的器件,自动控制是一个复合型的学科?控制工程师的工作需要具有力学,电子学,机械电子,流体力学,结构学,无料的各方面的知识?计算机在控制策略的执行中具有广泛的应用,并且控制工程的需求带动了信息技术的与软件工程的发展? 通常控制系统的范畴包括开环控制系统与闭环控制系统,两种系统的区别在于是否在系统中加入了闭环反馈装置? 开环控制系统 开环控制系统控制硬件形式很简单,图2.1描述了一个单容液位控制系统, 图2.1单容液位控制系统 我们的控制目标是保持容器的液位h 在水流出流量V 1变化的情况下保持在一定 可接受的范围内,可以通过调节入口流量V 2实现?这个系统不是精确的系统,本系 统无法精确地检测输出流量V 2,输入流量V 1以及容器液位高度?图2.2描述了这 个系统存在的输入(期望的液位)与输出(实际液位)之间的简单关系, 图2.2液位控制系统框图 这种信号流之间的物理关系的描述称为框图?箭头用来描述输入进入系统,以及
Hydraulic machinery and pump Hydraulic machinery are machines and tools which use fluid power to do work. Heavy equipment is a common example. In this type of machine, high-pressure liquid - called hydraulic fluid - is transmitted throughout the machine to various hydraulic motors and hydraulic cylinders. The fluid is controlled directly or automatically by control valves and distributed through hoses and tubes. The popularity of hydraulic machinery is due to the very large amount of power that can be transferred through small tubes and flexible hoses, and the high power density and wide array of actuators that can make use of this power. Hydraulic machinery is operated by the use of hydraulics, where a liquid is the powering medium. Pneumatics, on the other side, is based on the use of a gas as the medium for power transmission, generation and control. Hydraulic circuits For the hydraulic fluid to do work, it must flow to the actuator and or motors, then return to a reservoir. The fluid is then filtered and re-pumped. The path taken by hydraulic fluid is called a hydraulic circuit of which there are several types. Open center circuits use pumps which supply a
双吸离心泵毕业设计-开题报告
毕业设计(论文)开题报告 学生姓名：陈乐东学号：20121698 学院：机电工程学院 专业：热能动力工程 设计(论文)题目：800S26型双吸泵的设计 指导教师：杨辉 2016年2月15日
开题报告填写要求 1．开题报告（含“文献综述”）作为毕业设计（论文）答辩委员会对学生答辩资格审查的依据材料之一。此报告应在指导教师指导下，由学生在毕业设计（论文）工作前期内完成，经指导教师签署意见及所在专业审查后生效； 2．开题报告内容必须用黑墨水笔工整书写或按教务处统一设计的电子文档标准格式（可从教务处网页上下载）打印，禁止打印在其它纸上后剪贴，完成后应及时交给指导教师签署意见； 3．“文献综述”应按论文的格式成文，并直接书写（或打印）在本开题报告第一栏目内，学生写文献综述的参考文献应不少于15篇； 4．有关年月日等日期，按照如“2002年4月26日”方式填写。
1．结合毕业设计（论文）课题情况，根据所查阅的文献资料，每人撰写1500字左右的文献综述（包括研究进展，选题依据、目的、意义） 文献综述 800S26型双吸泵的型号意义是，入口直径为800mm，设计点扬程为26m的单极双吸水平中开式离心清水泵。要想了解此泵，首先要了解双吸离心泵。 双吸离心泵是从叶轮两面进水的双吸离心泵，因泵盖和泵体是采用水平接缝进行装配的，又称为水平中开式离心泵。与单级单吸离心泵相比，效率高、流量大、扬程较高。但体积大，比较笨重，一般用于固定作业。适用于丘陵、高原中等面积的灌区，也适用于工厂、矿山、城市给排水等方面。 S型单极双吸离心泵也被称为为中开式离心泵，供抽送清水或物理化学性质类似于水的其他液体之用。S系列单级双吸离心泵主要适用于自来水厂、空调循环用水、建筑供水、灌溉、排水泵站、电站、工业供水系统、消防系统、船舶工业等输送液体的场合。 S型中开泵与其他同类型泵相比较具有寿命长、效率高、结构合理，运行成本低、安装及维修方便等特点，是消防、空调、化工、水处理及其他行业的理想用泵。泵体设计压力为1.6MPa和2.0MPa。泵体的进出口法兰均位于下泵体，这样可以在不拆卸系统管路的情况下取出转子，维修方便。部分泵体采用双流道设计，以减少径向力，从而延长机封和轴承的寿命。叶轮叶轮的水力设计采用了最先进的 CFD 技术,因此提高了S泵的水力效率。对叶轮进行动平衡, 确保S泵的运行平稳。轴轴径较粗,轴承间距较短,从而减小了轴的挠度,延长了机械密封和轴承的寿命。轴套可以采用多种不同的材料,以防止轴被腐蚀和磨损,轴套可更换。磨损环泵体与叶轮间采用可更换的磨损环,防止泵体和叶轮的磨损,更换方便,维修费用低,同时保证运行间隙和较高的工作效率。既可以使用填料也可以使用机械密封,可以在不拆卸泵盖的情况下更换密封装置。轴承独特的轴承体设计使轴承可采用油脂或稀油润滑,轴承的设计寿命10万小时以上,也可使用双列推力轴承和封闭轴承。材料根据用户的实际需要,S型中开泵的材料可为铜、铸铁、球铁、316不锈钢、416;7锈钢、双向钢、哈氏合金、蒙耐合金,钛合金及20号合金等材料。 我国水泵技术的现状 1、我国泵产品图样的来源可分为联合设计、引进、自行开发等几种，引进的这些
智能汽车中英文对照外文翻译文献 (文档含英文原文和中文翻译) 翻译： 基于智能汽车的智能控制研究 摘要：本文使用一个叫做“智能汽车”的平台进行智能控制研究，该小车采用飞思卡尔半导体公司制造的MC9S12DG128芯片作为主要的控制单元，同时介绍了最小的智能控制系统的设计和实现智能车的自我追踪驾驶使用路径识别算法。智能控制智能车的研究包括:提取路径信息,自我跟踪算法实现和方向和速度控制。下文介绍了系统中不同模块的各自实现功能，最重要部分是智能车的过程智能控制：开环控制和闭环控制的应用程序包括增量式PID控制算法和鲁棒控制算法。最后一步是
基于智能控制系统的智能测试。 关键词：MC9S12DG128；智能控制;开环控制；PID；鲁棒； 1.背景介绍 随着控制理论的提高以及信息技术的快速发展,智能控制在我们的社会中发挥着越来越重要的作用。由于嵌入式设备有小尺寸、低功耗、功能强大等优点，相信在这个领域将会有一个相对广泛的应用,如汽车电子、航空航天、智能家居。如果这些技术一起工作，它将会蔓延到其他领域。为了研究嵌入式智能控制技术，“智能汽车”被选为研究平台,并把MC9S12DG128芯片作为主控单元。通过智能控制,智能汽车可以自主移动,同时跟踪的路径。 首先,本文给读者一个总体介绍智能车辆系统的[2、3]。然后,根据智能车辆的智能控制:提取路径信息,自我跟踪算法实现中,舵机的方向和速度的控制。它提供包括了上述四个方面的细节的智能车系统信息。此外,本文强调了智能车的控制过程应用程序包括开环控制、闭环增量PID算法和鲁棒算法。 2.智能车系统的总体设计 该系统采用MC9S12DG128[4]作为主芯片，以及一个CCD传感器作为交通信息收集的传感器。速度传感器是基于无线电型光电管的原理开发。路径可以CCD传感器后绘制收集的数据，并且系统计算出相应的处理。在同时，用由电动马达速度测试模块测量的智能汽车的当前速度进行响应的系统。最后，路径识别系统利用所述路径信息和当前的速度，以使智能汽车在不同的道路条件的最高速度运行。图1示出了智能车辆系统的框图。
1、 外文原文 A: Fundamentals of Single-chip Microcomputer Th e si ng le -c hi p m ic ro co mp ut er i s t he c ul mi na ti on of both t h e de ve lo pm en t o f t he d ig it al co m pu te r an d th e i n te gr at ed c i rc ui t a rg ua bl y t h e to w m os t s ig ni f ic an t i nv en ti on s o f t he 20th c e nt ur y [1]. Th es e t ow ty pe s of ar ch it ec tu re a re fo un d i n s in g le -ch i p m i cr oc om pu te r. So m e em pl oy t he spl i t pr og ra m/da ta m e mo ry o f th e H a rv ar d ar ch it ect u re , sh ow n in Fi g.3-5A -1, o th ers fo ll ow t he p h il os op hy , wi del y a da pt ed f or ge n er al -p ur po se co m pu te rs a nd m i cr op ro ce ss o r s, o f ma ki ng n o log i ca l di st in ct ion be tw ee n p r og ra m an d d at a m e mo ry a s i n t he P r in ce to n ar ch ite c tu re , sh ow n i n F ig.3-5A-2. In g en er al te r ms a s in gl e -chi p m ic ro co mp ut er i s c h ar ac te ri ze d b y t h e i nc or po ra ti on o f a ll t he un it s of a co mp uter i n to a s in gl e d ev i ce , as s ho wn in Fi g3-5A -3. Fig.3-5A-1 A Harvard type Program memory Data memory CPU Input& Output unit memory CPU Input& Output unit
利用神经网络预测轴向柱塞泵的性能 Mansour A Karkoub a, Osama E Gad a, Mahmoud G Rabie b a--就读于科威特的科威特大学工程与石油学院 b--就读于埃及开罗的军事科技大学 摘要 本文推导了应用于轴向柱塞泵（斜轴式）的神经网络模型。该模型采用的数据是由一个实验装置获得的。这个正在进行的研究的目的是降低柱塞泵在高压下工作时的能量损耗。然而，在最初我们要做一些研究来预测当前所设计的泵的响应。神经网络模型具有前反馈的结构，并在测验过程中使用Levenberg-Marquardt优化技术。该模型能够准确地预测柱塞泵的动态响应。 1、简介 可变排量轴向柱塞泵是在流体动力系统中经常要用到的重要设备，如液压动力供应控制和静液压传动驱动器的控制。本装置具有变量机制和功率-重量比特性，使其最适合于高功率电平的控制。所设计的这种轴向柱塞泵拥有可靠性和简便的特点，然而其最重要的特征是可以变量输出。 人们在轴向柱塞泵领域已经做了很多研究，但是本文将只论述一下少数几人所做的贡献。 Kaliafetis和Costopoulos[5]用调压器研究了轴向柱塞变量泵的静态和动态特性。所提出的模型的精确度依赖于制造商提供的动态运行曲线等数据。他们得出结论，运行条件对泵的动态行为是非常关键的，而泵的动态行为可以通过减小压力设定值进行改善。Harris等人[4]模拟和测量了轴向柱塞泵的缸体压力和进油流量脉动。Kiyoshi和Masakasu[7]研究了斜盘式变量输送的轴向柱塞泵在运行时刻的实验上和理论上的静态和动态特性。并提出了一种新的方法来预测泵在运行过程中的响应。也对研究泵特性的新方法的有效性进行了实验验证，实验中使用了一个有宽、短而深的凹槽的配流盘。Edge和Darling[2]研究了液压轴向柱塞泵的缸体压力和流量。这个得出的模型经过了实验检验。对于配流盘、缸体上设计的退刀槽和泵的流量脉动对泵特性的影响都进行了验证。 人们已证实了一种可替代的建模技术——神经网络（NN）能取得良好的效果，特别是对于高度非线性的系统。这种技术是模仿人脑获取信息的功能。Karkoub 和Elkamel[6]用神经网络模型预测了一个长方形的气压轴承的压力分布。所设计的这种模型在预测压力分布和承载能力方面比其他可用的工具更加精确。Gharbi 等人[3]利用神经网络预测了突破采油。其表现远远优于常见的回归模型或有限差分法。李等人[8]用神经网络模型NNS和鲍威尔优化技术对单链路和双链路的倒立摆进行了建模和控制。研究者们取得了理想的结果。Panda等人[9]应用NNS在普拉德霍湾油田对流体接触进行了建模。所得到的模型预测的目标油井中的流量分配比传统的以回归为基础的技术更准确。Aoyama等人[1]已经推导出一个神经网络模型来预测非最小相系统的响应。所开发出的的模型被应用于Van de Vuss反应器和连续搅拌式生物反应器，所得到的结果是令人满意的。 本文研究利用神经网络解决轴向柱塞泵（斜轴式）在一定的供油压力下的建模。本文首先会描述用于收集实验数据的实验装置，然后将会简要介绍神经网络建模程序。 2、实验装置
各种水泵英文翻译 abration resisting pump ,,,,, 耐磨泵； absorption pump ,,,,, 吸收泵； acid pump ,,,,, 耐酸泵； activated sludge pump ,,,,, 活性污泥泵 adjustable diaphragm pump ,,,,, 可调隔膜泵； adjustable discharge gear pump ,,,,, 齿轮比例泵； adsorption vacuum pump ,,,,, 吸附真空泵； agricultural spray pump ,,,,, 喷灌泵； agricultural spray pump for chemicals ,,,,, 农用喷药泵； air lift pump ,,,,, 气泡泵；曼木特泵；气举泵； air operated pump ,,,,, 压缩空气驱动泵； air-powered piston pump ,,,,, 风动活塞泵； air-pressure actuated slurry pump ,,,,, 气动泥浆泵； airtight screw pump ,,,,, 密闭式螺杆泵； all abronze pump ,,,,, 全青铜泵； all iron pump ,,,,, 铸铁泵； alloy pump ,,,,, 合金泵； alloy steel pump ,,,,, 合金钢泵； angle-type axial flow pump ,,,,, 半贯流式轴流泵；弯管轴流泵； angle-type axial piston pump ,,,,, 斜轴式轴向活塞泵； animal self-operated drinking water pump ,,,,, 饲槽自动泵；家畜自动饮水泵；annular casing pump ,,,,, 环壳泵； anti-roll pump ,,,,, 减摇泵； Archimedean screw pump ,,,,, 螺旋泵； armoured pump ,,,,, 铠装泵； articulated vane pump ,,,,, 铰链滑片泵； ash pump ,,,,, 灰渣泵； attached pump ,,,,, 附属泵； automatic trough pump ,,,,, 饲槽自动泵；家畜自动引水泵； automobile pump ,,,,, 汽车用泵； auxiliary pump ,,,,, 辅泵；辅助泵； auxiliary stripping pump ,,,,, 辅扫仓泵；辅清仓泵； aviation pump ,,,,, 航空用泵； axial double entry liquid ring pump ,,,,, 轴向双吸液环泵； axial flow ,,,,, 轴流泵； axial flow pump for water jet propulsion ,,,,, 喷水推进轴流泵； axial flow pump with adjustable pitch blades ,,,,, 可调式轴流泵； axial flow pump with blades adjustable in operation ,,,,, 全可调式轴流泵axial flow pump with blades adjustable when stationary ,,,,, 半可调式轴流泵；axial flow pump with variable pitch blades ,,,,, 全可调式轴流泵； axial flowpump with reversible blades ,,,,, 可逆叶片轴流泵； axial inlet pump ,,,,, 轴吸泵；
本科生毕业设计（论文）外文翻译毕业设计（论文）题目：悬架系统设计与分析 外文题目：An Overview of Disarray in Active Suspension System 译文题目：主动悬架系统杂谈 学生姓名： XXX 专业：车辆工程1002班 指导教师姓名：田国富 评阅日期：
主动悬架系统杂谈 帕蒂尔，维杰河帕蒂尔，加尼甚 助理教授，机械工程系，A.D.C.E.T，阿什达 摘要：当设计一个悬挂系统时，它的双重目标是尽量减少传到乘客的垂直力量和最大限度地提高轮胎与道路接触以提高操控性和安全性。乘客的舒适性与从车身传递的垂直力有关。这个目标可以通过最小化车身的垂直加速度来实现。过度的车轮行驶，将导致轮胎相对路面的非最佳姿态，从而导致差的操控性和附着力。此外，为了保持良好的操控性，轮胎与路面的最佳接触必须保持在四个轮子上。在传统的悬架系统中，这些特点是冲突的，不符合所有条件。因此，在被动悬架系统的基础上，为了改善主动悬架系统，各种各样的研究工作正在进行中。在本文中各种作品的概述已经完成。考虑到季度汽车模型，本文试图给出关于以往的研究和他们的发现对被动和主动悬架系统的参数。 关键词：主动悬架系统，控制系统，动态，被动悬架，车辆。 1.引言 汽车悬架系统的目的是在不同路况下，能保持良好的操控特性和改善乘坐品质。不同的悬架，满足上述要求的程度不同。虽然，可由设计者的聪明才智来改善，就平均而言，悬架的性能主要取决于悬架使用的类型。按改进的性能可以以升序区分为：与被动，半主动和全主动悬架系统，输入的力通常由液压致动器提供。为主动悬架系统设计的机电致动器的另一种方法将在电子控制和悬架系统之间提供直接接口。 目前，公认的主动悬架有两种形式，一种是制动器和钢板弹簧平行的高带宽主动悬架。第二种是低带宽主动悬架，它的致动器带有一系列的钢板弹簧并且能够控制车身的运动，而簧下质量控制是通过被动阻尼器控制的。汽车悬架的主动控制在传统悬架的基础上又提出了新的改进。主动悬架，包括创建悬挂系统中力的液压致动器。由液压致动器产生的力被用来控制簧上质量的运动，以及簧上和簧下质量之间的相对速度。为了提高车辆的特色，以后将主要对主动悬架的高带宽型进行研究。
电厂蒸汽动力的基础和使用 1.1 为何需要了解蒸汽 对于目前为止最大的发电工业部门来说, 蒸汽动力是最为基础性的。 若没有蒸汽动力, 社会的样子将会变得和现在大为不同。我们将不得已的去依靠水力发电厂、风车、电池、太阳能蓄电池和燃料电池,这些方法只能为我们平日用电提供很小的一部分。 蒸汽是很重要的,产生和使用蒸汽的安全与效率取决于怎样控制和应用仪表,在术语中通常被简写成C&I(控制和仪表 。此书旨在在发电厂的工程规程和电子学、仪器仪表以 及控制工程之间架设一座桥梁。 作为开篇,我将在本章大体描述由水到蒸汽的形态变化,然后将叙述蒸汽产生和使用的基本原则的概述。这看似简单的课题实际上却极为复杂。这里, 我们有必要做一个概述:这本书不是内容详尽的论文,有的时候甚至会掩盖一些细节, 而这些细节将会使热力学家 和燃烧物理学家都为之一震。但我们应该了解,这本书的目的是为了使控制仪表工程师充 分理解这一课题,从而可以安全的处理实用控制系统设计、运作、维护等方面的问题。1.2沸腾:水到蒸汽的状态变化 当水被加热时,其温度变化能通过某种途径被察觉(例如用温度计 。通过这种方式 得到的热量因为在某时水开始沸腾时其效果可被察觉,因而被称为感热。 然而,我们还需要更深的了解。“沸腾”究竟是什么含义?在深入了解之前,我们必须考虑到物质的三种状态:固态,液态,气态。 (当气体中的原子被电离时所产生的等离子气体经常被认为是物质的第四种状态, 但在实际应用中, 只需考虑以上三种状态固态,
物质由分子通过分子间的吸引力紧紧地靠在一起。当物质吸收热量,分子的能量升级并且 使得分子之间的间隙增大。当越来越多的能量被吸收,这种效果就会加剧,粒子之间相互脱离。这种由固态到液态的状态变化通常被称之为熔化。 当液体吸收了更多的热量时,一些分子获得了足够多的能量而从表面脱离,这个过程 被称为蒸发(凭此洒在地面的水会逐渐的消失在蒸发的过程中,一些分子是在相当低的 温度下脱离的,然而随着温度的上升,分子更加迅速的脱离,并且在某一温度上液体内部 变得非常剧烈,大量的气泡向液体表面升起。在这时我们称液体开始沸腾。这个过程是变为蒸汽的过程,也就是液体处于汽化状态。 让我们试想大量的水装在一个敞开的容器内。液体表面的空气对液体施加了一定的压 力,随着液体温度的上升,便会有足够的能量使得表面的分子挣脱出去,水这时开始改变 自身的状态,变成蒸汽。在此条件下获得更多的热量将不会引起温度上的明显变化。所增 加的能量只是被用来改变液体的状态。它的效用不能用温度计测量出来,但是它仍然发生 着。正因为如此,它被称为是潜在的,而不是可认知的热量。使这一现象发生的温度被称为是沸点。在常温常压下,水的沸点为100摄氏度。 如果液体表面的压力上升, 需要更多的能量才可以使得水变为蒸汽的状态。 换句话说, 必须使得温度更高才可以使它沸腾。总而言之,如果大气压力比正常值升高百分之十,水必须被加热到一百零二度才可以使之沸腾。
附件1：外文资料翻译译文 1 液压传动概述 1.1 液压传动的发展概况 1.1.1 压传动的定义 一部完整的机器是由原动机部分、传动机构、控制部分及工作机部分组成。原动机有几种类型，例如电动机、内燃机等。工作机即完成该机器的工作任务的直接工作部分，如剪床的剪刀，车床的刀架、车刀、卡盘等。由于原动机的功率和转速比是被限制的，为了覆盖工作机较大范围的工作力和工作速度的变化，以及操作性能的要求，在原动机和工作机之间设置了传动机构，其作用是把原动机输出功率经过变换后传递给工作机。 传动机构通常分为电气传动、机械传动和流体传动三类机构。流体传动是通过液压、流体或气体来进行能量传递和控制的。但需要认识到实际上只有两种液压系统：液力传动和液压传动（包括液力和气体）。 液压传动和液力传动均是以液体作为工作介质来进行能量传递的传达方式。液力传动则主要是利用液体的动能来传递能量；而液压传动主要是利用液体的压力能来传递能量。由于液压传动有许多突出的优点，因此，它被广泛的应用于工业的每个分支。一些典型的运用像机械工程、建筑、海洋开发、交通运输、农业和航天航空 1.1.2 液压传动的发展概况 到18世纪中叶的工业革命，电能已经不能支持工业机器的传动需求。18世纪末液压传动被用于驱动液力设备，例如起重机、压力机、绞车、压榨机、液力千斤顶、修剪机械、和支承机械。在这些系统中，是一种由蒸汽机驱动液力的水泵，这种泵是通过压力将水通过管道传到工业机械来驱动各种机器的。这些早期的液力系统有着许多的不足，例如设计问题，由于设计已经发展为艺术而多过了科学。然而，直到19世纪电力成为新的有优势的技术。这样的结果液压传动并没有起到推动的作用。电力传动不久被发现在远距离传递上有良好的效果。在19世纪最后的10年里液压传动技术只有小小的发展。近代，1906年液压传动开始被重视，是当时用液
CENTRIFUGAL PUMP IN CHEMICALPRODUCTIONAPPLICATION Centrifugal pump in chemical production, this is most widely used because of its performance wide range (including flow, pressure head of media properties and ShiYing sexual), small volume, simple structure, easy operation, flow uniformity, low malfunction, long service life, CaoZuoFei are lower cost and prominent advantages. (1)centrifugal pump principle of work Centrifugal pump working principle is: centrifugal pump so can turn the water away is because only centrificating. Water pump before work, pump body and feed water full line must be cans in vacuum condition, when the impeller fast turns, leaf prompted water quickly spin, spin in the water under the action of the centrifugal force, pump impeller flew in from the water was thrown in the central part of the impeller, after forming vacuum area. Water in the water atmospheric pressure (or water pressure) under the action of water pipe pressure came through a tube. This cycle unceasingly, can achieve continuous pumped. In the centrifugal pump is worth mentioning: before initiating must to the pump housing filled with water, can start after, otherwise will cause, the vibration of the pump body, thus reduce heat pump, damage to (hereinafter referred to as "cavitation erosion") cause equipment accident! Centrifugal pump is a lot of more phyletic, classification methods common has the following kinds of kind: 1, press the impeller inhaled way points: single suction style centrifugal pump double suction type centrifugal pump. 2, press the impeller number points: single grade centrifugal pump mulfistage centrifugal pump. 3, according to the structure of impeller points: open impeller centrifugal pump impeller half open centrifugal pump closed impeller centrifugal pump. 4, according to work pressure points: low voltage centrifugal pump medium centrifugal pump high-pressure centrifugal pump. 5, according to pump shaft position points: horizontal centrifugal pump edge vertical centrifugal pump. (2) basic structure, centrifugal pumps
Background of Control Theory System and Control Theory According to the Encyclopedia Americana，a system is "an aggregation ox assemblage of things so combined by nature or man as to form an integral and complex whale". Mathematical systems theory is the study，of the interruptions and behavior of such an assemblage of "things'* when subjected to certain conditions or inputs. The abstract nature of systems theory is due to the fact that it is concerned with mathematical properties rather than the physical faun of the constituent parts. Control theory is mare often concerned with physical applications. A control system is considered to he any system which exists for the purpose or regulating or controlling the flow of energy，information, money，or other quantities in some desired fashion. In more general terms，a control system is an interconnection of many components or functional units in such a way as to produce a desired result. In this book，control theory is assumed to encompass all questions related to design and analysis of control systems. Fig. 37. 1 is a general representation of an open loop control system, the ingot or control u(t) is selected hayed on the goals for the system and all available a priori knowledge about the system, The input is in no way influenced by the output of the system，represented by y(t)，If unexpected disturbances act upon an open-loop system, or if its behavior is not completely understood，them the output will not behave precisely as expected.
电气工程与自动化学院 本科毕业设计专业翻译资料（中文读书报告） 学生姓名：王超杰 专业班级：自动化12-06班 学号：311208002219 2016 年 6 月11 日
原文： Design of Combustible Gas Detection system using Wireless Transmission Technology Shijiazhuang Universities of Economics, Hebei, China zkzhlp@https://www.doczj.com/doc/059680994.html, Keywords:TGS813, AT89S52, DS18B20, nRF905, TC35i Abstract.The detection device of combustible gas are designed in the presented work,using wireless transceiver and GSM network.The system realize the wireless transmission of the gas concentration,and also can send alarm information to user’s mobile when an exception occurs. The system consists of two parts: a master and slave. The function of the slave is to collect data, process data and transffer the data to the master.The taskof the master is to receive data and display it by LED. The signal acquisition is completed by sensor TGS813 and A/D converter TLC2543. The wireless transmission is achieved through wireless transceiver nRF905. Since the accuracy of the sensor is affected by the environment,using DS18B20 to achieve temperature compensation. And with wireless communication module TC35i and GSM network platform, we can send the alarm information to user’s mobile promptly. Introduction Gas detection is widely used in petroleum, chemical, metallurgy, family, shopping malls, gas stations and other places. Currently, how to monitor the hazardous gas fast and accurately are the important issues. Although the gas detection technology is relatively mature, but most products has many shortcomings, such as single function, operating complex, bulky, expensive and low sensitivity. Wireless communication technology applied to the gas monitoring field, can resolve the problem of remote monitoring in special environment, such as high temperature, low temperature, toxic gas.and unable to wiring . In the presented work, the combustible gas detectoris fully functional (with wireless transceiver), simple, small size, low cost, and has high sensitivity. The equipment can greatly improve the system's detection capability and accuracy with temperature compensation algorithm, and also can send alarm information to the user's mobile phone promptly through the GSM network. System design The system consists of two parts as shown in Figure 1. Fig. 1 Overall system block diagram