Web Server for Embedded Systems
After the “everybody-in-the-Internet-wave” now obviously follows the
“everything-in-the-Internet-wave”.The most coffee, vending and washing
machines are still not available about the worldwide net. However the embedded
Internet integration for remote maintenance and diagnostic as well as the so-called
M2M communication is growing with a considerable speed rate.
Just the remote maintenance and diagnostic of components and systems by Web
browsers via the Internet, or a local Intranet has a very high weight for many
development projects. In numerous development departments people work on
completely Web based configurations and services for embedded systems. The
remaining days of the classic user interface made by a small LC-display with front
panel and a few function keys are over. Through future evolutions in the field of
the mobile Internet, Bluetooth-based PAN s (Personal Area Network's) and
the rapidly growing M2M communication (M2M=Machine-to-Machine)
a further innovating advance is to be expected.
The central function unit to get access on an embedded system via Web browser is
the Web server. Such Web servers bring the desired HTML pages (HTML=Hyper
Text Markup Language) and pictures over the worldwide Internet
or a local network to the Web browser. This happens HTTP-based (Hyper
Text Transfer Protocol). A TCP/IP protocol stack –that means it is based on
sophisticated and established standards–manages the entire communication.
Web server (HTTP server) and browser (HTTP client) build TCP/IP-
applications. HTTP achieved a phenomenal distribution in the last years.
Meanwhile millions of user around the world surf HTTP-based in the World
Wide Web. Today almost every personal computer offers the necessary
assistance for this protocol. This status is valid more and more for embedded
systems also. The HTTP spreads up with a fast rate too.
1. TCP/IP-based HTTP as Communication Platform
HTTP is a simple protocol that is based on a TCP/IP protocol stack (picture 1.A).
HTTP uses TCP (Transmission Control Protocol). TCP is a relative complex and
high-quality protocol to transfer data by the subordinate IP protocol. TCP itself
always guarantees a safeguarded connection between two communication partners
based on an extensive three-way-handshake procedure. As a
result the data transfer via HTTP is always protected. Due to
the extensive TCP protocol mechanisms HTTP offers only a low-grade
performance.
Figure 1: TCP/IP stack and HTTP programming model
HTTP is based on a simple client/server-concept. HTTP server and client
communicate via a TCP connection. As default TCP port value the port number
80 will be used. The server works completely passive. He waits for a request
(order) of a client. This request normally refers to the transmition of specific
HTML documents. This HTML documents possibly have to be generated
dynamically by CGI. As result of the requests, the server will answer with a
response that usually contains the desired HTML documents among others
(picture 1.B).
GET /test.htm HTTP/1.1
Accept]: image/gif, image/jpeg, */*
User selling agent: Mozilla/4.0
Host: 192.168.0.1
Listing 1.A: HTTP GET-request
HTTP/1.1 200 OK
Date: Mon, 06 Dec 1999 20:55:12 GMT
Server: Apache/1.3.6 (Linux)
Content-length: 82
Content-type: text/html
Test-Seite
The DIL/NetPCs DNP/1110 – Using the Embedded Linux
Listing 1.B: HTTP response as result of the GET-request from listing 1.A
HTTP requests normally consist of several text lines, which are transmitted to the
server by TCP. The listing 1.A shows an example. The first line characterizes the
request type (GET), the requested object (/test1.htm) and the used HTTP version
(HTTP/1.1). In the second request line the client tells the server, which kind of
files it is able to evaluate. The third line includes information about the
client- software. The fourth and last line of the request from listing 1.A is used to
inform the server about the IP address of the client. In according to the type of
request and the used client software there could follow some further lines. As
an end of the request a blank line is expected.
The HTTP responses as request answer mostly consist of two parts. At first there
is a header of individual lines of text. Then follows a content object (optional).
This content object maybe consists of some text lines –in case of a HTML file– or
a binary file when a GIF or JPEG image should be transferred. The first line of the
header is especially important. It works as status or error message. If an
error occurs, only the header or a part of it will be transmitted as answer.
2. Functional principle of a Web Server
Simplified a Web server can be imagined like a special kind of a file server.
Picture 2.A shows an overview. The Web server receives a HTTP GET-request
from the Web browser. By this request, a specific file is required as answer (see
step 1 into picture 2.A). After that, the Web server tries to get access on the file
system of the requested computer. Then it attempts to find the desired file (step 2).
After the successful search the Web server read the entire file
(step 3) and transmit it as an answer (HTTP response comprising of header
and content object) to the Web browser (step 4). If the Web server cannot find
the appropriate file in the file system, an error message (HTTP response which
only contains the header) is simply be send as response to the client.
Figure 2: Functional principle from Web server and browser
The web content is build by individual files. The base is build by static files with
HTML pages. Within such HTML files there are references to further files
embedded –these files are typically pictures in GIF or JPEG format. However,
also references to other objects, for example Java-Applets, are possible. After a
Web browser has received a HTML file of a Web server, this file will be
evaluated and then searched for external references. Now the steps 1 to 4 from
picture 2.A will run again for every external reference in order to request the
respective file from the corresponding Web server. Please note, that such a
reference consists of the name or IP address of a Web server (e.g. "https://www.doczj.com/doc/8e8322778.html,"),
as well as the name of the desired file (e.g. "picture1.gif"). So virtually every
reference can refer to another Web server. In other words, a HTML file could be
located on the server "ssv-embedded.de" but the required picture -which is
external referenced by this HTML file- is located on the Web server
"https://www.doczj.com/doc/8e8322778.html,". Finally this (worldwide) networking of separate objects is the
cause for the name World Wide Web (WWW). All files, which are required by a
Web server, are requested from a browser like the procedure shown on picture
2.A. Normally these files are stored in the file system of the server. The
Webmaster has to update these files from time to time.
A further elementary functionality of a Web server is the Common
Gateway Interface(CGI) -we have mentioned before. Originally this technology
is made only for simple forms, which are embedded into HTML pages. The data,
resulting from the padding of a form, will be transmitted to a Web server via
HTTP-GET or POST-request (see step 1 into picture 2.B). In such a GET- or
POST-request the name of the CGI program, which is needed for the
evaluation of a form, is fundamentally included. This program has to be on the
Web server. Normally the directory "/cgi-bin" is used as storage location.
As result of the GET- or POST-request the Web server starts the CGI program
located in the subdirectory "/cgi-bin" and delivers the received data in form of
parameters (step 2). The outputs of a CGI program are guided to the Web server
(step 3). Then the Web server sends them all as responses to the Web browser
(step 4).
3. Dynamic generated HTML Pages
In contradiction to a company Web site server, which informs people about the
product program and services by static pages and pictures, an embedded
Web server has to supply dynamically generated contents. The embedded Web
server will generate the dynamic pages in the moment of the first access by a
browser. How else could we check the actual temperature of a system via
Internet? Static HTML files are not interesting for an embedded Web server.
The most information about the firmware version and service instructions are
stored in HTML format. All other tasks are normally made via dynamic generated
HTML.
There are two different technologies to generate a specific HTML page in the
moment of the request: First the so-called server-side-scripting and second
the CGI programming. At the server-side-scripting, script code is embedded
into a HTML page. If required, this code will be carried out on the server (server-
sided).
For this, there are numerous script languages available. All these languages are
usable inside a HTML-page. In the Linux community PHP is used mostly. The
favourite of Microsoft is VBScript. It is also possible to insert Java directly into
HTML pages. Sun has named this technology JSP(Java Server Pages).
The HTML page with the script code is statically stored in the file system of the
Web server. Before this server file is delivered to the client, a special program
replaces the entire script code with dynamic generated standard HTML. The Web
browser will not see anything from the script language.
Figure 3: Single steps of the Server-Side-Scripting
Picture 3 shows the single steps of the server-side-scripting. In step 1 the Web
browser requests a specific HTML file via HTTP GET-request. The Web server
recognizes the specific extension of the desired file (for example *.ASP or *.PHP
instead of *.HTM and/or *.HTML) and starts a so-called scripting engine
(see step 2). This program gets the desired HTML file including the script code
from the file system (step 3), carry out the script code and make a new
HTML file without script code (step 4). The included script code will be replaced
by dynamic generated HTML. This new HTML file will be read by the Web
server (step 5) and send to the Web browser (step 6). If a server-sided scripting is
supposed to be used by an embedded Web server, so you have
to consider the necessary additional resources. A simple example: In order
to carry out the embedded PHP code into a HTML page, additional program
modules are necessary for the server. A scripting engine together with the
embedded Web server has to be stored in the Flash memory chip of an embedded
system. Through that, during run time more main memory is required.
4. Web Server running under Linux
Once spoken about Web servers in connection with Linux most people
immediately think of Apache. After investigations of the Netcraft Survey
this program is the mostly used Web server worldwide. Apache is an
enhancement of the legendary NCSA server. The name Apache itself has
nothing to do with Red Indians. It is a construct from "A Patchy Server" because
the first version was put together from different code and patch files.
Moreover there are numerous other Web servers - even for Linux. Most of this are
standing under the GPL (like Apache) and can be used license free. A
very extensive overview you can find at "https://www.doczj.com/doc/8e8322778.html,/". Every
Web server has his advantages and disadvantages. Some are developed for
specific functions and have very special qualities. Other distinguishes at best
through their reaction rate at many simultaneous requests, as well
as the variety of their
configuration settings. Others are designed to need minimal resources and offer very small setting possibilities, as well as only one connection to a client.
The most important thing by an embedded Web server is the actual resource requirements. Sometimes embedded systems offer only minimal resources, which mostly has to be shared with Linux. Meanwhile there are numerous high- performance 32-bit-386/486-microcontroller or (Strong)ARM-based embedded systems that own just 8 Mbytes RAM and 2 Mbytes Flash-ROM (picture 4). Outgoing from this ROM (Read-only-Memory, i.e. Flash memory chips) a complete Linux, based on a 2.2- or 2.4-Kernel with TCP/IP protocol stack and Web server, will be booted. HTML pages and programs are also stored in the ROM to generate the dynamic Web pages. The space requirements of an embedded system are similar to a little bigger stamp. There it is quite understandable that there is no place for a powerful Web server like Apache.
Figure 4: Embedded Web Server Module with StrongARM and Linux
But also the capability of an Apache is not needed to visualize the counter of a photocopier or the status of a percolator by Web servers and browsers. In most cases a single Web server is quite enough. Two of such representatives are boa (https://www.doczj.com/doc/8e8322778.html,) and thttpd (https://www.doczj.com/doc/8e8322778.html,). At first, both Web servers are used in connection with embedded systems running under Linux. The configuration settings for boa and thttpd are poor, but quite enough. By the way, the source code is available to the customer. The practicable binary files for these servers are always smaller than 80 Kbytes and can be integrated in the most embedded systems without problems. For the dynamic generation of HTML pages both servers only offer CGI (Common Gateway Interface) as enlargement. Further technologies, like server-side-includes (SSI) are not available.
The great difference between an embedded Web server and Apache is, next to the limited configuration settings, the maximal possible number of simultaneous requests. High performance servers like Apache immediately make an own process for every incoming call request of a client. Inside of this process all
further steps will then be executed. This requires a very good programming and a lot of free memory resources during run time. But, on the other hand many Web browsers can access such a Web server simultaneously. Embedded Web server like boa and thttpd work only with one single process. If two users need to get access onto a embedded Web server simultaneously, one of both have to wait a few fractions of a second. But in the environment of the embedded systems that is absolutely justifiable. In this case it is first of all a question of remote maintenance, remote configuration and similar tasks. There are not many simultaneous requests expected.
The DIL/NetPCs DNP/1110 – Using the Embedded Linux
List of Figures
Figure 1: TCP/IP stack and HTTP programming model
Figure 2: Functional principle from Web server and browser
Figure 3: Single steps of the Server-Side-Scripting
Figure 4: Embedded Web Server Module with StrongARM and Linux
Listings
Listing 1.A: HTTP GET-request
Listing 1.B: HTTP response as result of the GET-request from listing 1.A Contact
SSV Embedded Systems
Heisterbergallee 72
D-30453 Hannover
Tel. +49-(0)511-40000-0
Fax. +49-(0)511-40000-40
Email: sales@ist1.de
Web: www.ssv-embedded.de
Document History (Sadnp05.Doc)
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嵌入式系统的网络服务器
在“每个人都处在互联网的浪潮中”之后，现在很明显随之而来的是“每件事都处在互联网的浪潮中”。大多数售卖咖啡的机器仍然不能提供全世界的联网。然而嵌入式远程维护和诊断的网络集成就像所谓的M2M通信一样以一种相当快的速度增长。
对很多发展工程来说，仅仅是通过网络浏览器经Internet，或是经过局域网进行组成和系统的远程维护和诊断，负担非常之重。在许多部门中，人们对于嵌入式系统配置和服务的工作完全地基于网络。剩余的时间用前面的面板和一些功能键组成一个小的LC显示结束经典用户界面的制作。随着移动互联网领域将来的发展，可以预期，基于蓝牙技术的个人区域网和快速发展的M2M通信会出现长足的进步。
经过网络浏览器获得进入一个嵌入式系统最主要的功能单元是网络服务器。这种网络服务器给网络浏览器带来全球互联网或局域网上理想的HTML页（HTML —Hypertext Markup Language, 超文本链接标示语言）和图片。这样发生了基于HTTP（HTTP —Hypertext Transfer Protocol, WWW服务程序所用的协议）。一个TCP/IP协议层，意味着基于这个已制定的标准，来管理整个通信。网络服务器（HTTP服务器端）和浏览器（HTTP客户端）构建了TCP/IP的应用软件。HTTP在去年达到了一个显著的区分。其间全世界数以百万计的用户在广域网中使用基于HTTP进行冲浪。今天几乎每一台个人电脑都对这个协议提供了必要的支持。这种状况在嵌入式系统中也越来越多。HTTP在以极快的速度伸展。
1．基于TCP/IP的HTTP作为通信平台
HTTP是一个基于TCP/IP协议层之上的简单的协议。HTTP使用TCP（TCP－Transfer Control Protocol, 传输控制协议）。TCP是一个通过下属的IP（IP －Internet Protocol, 网际协议）协议传输数据的相对复杂和高质量的协议。TCP本身经过一个广泛的三方握手程序，始终保证两个通信伙伴之间安全的连接。因此经过HTTP的数据传输可以始终被保护。由于广泛的TCP协议机制，HTTP只表现出一种低级别的性能。
Figure 1: TCP/IP stack and HTTP programming model
HTTP基于一种简单的客户/服务器的概念。HTTP服务器和客户端经过一个TCP连接进行通信。默认的端口号是80。服务器完全被动地工作。他等待客户端的请求。这种请求通常指明确的HTML文件的传输。这种HTML文件可能不得不由CGI（CGI－Common Gateway Interface , 公共网关接口）动态产生。请求的结果，服务器通常将包含的需要的HTML文件通过响应回答(Picture 1.B)。
HTTP的请求通常由几行文本组成，通过TCP传送到服务器。Listing 1.A给出了一个例子。第一行表明了请求类型（GET），请求对象（/test1.htm）以及使用HTTP的版本（HTTP/1.1）。请求的第二行客户端告诉服务器能够接收什么类型的文件。第三行包括了关于客户端软件的信息。请求的第四行也是最后一行通知服务器客户端的IP地址。依照请求的类型以及应用的客户端软件可以写出更多行。可以用一个空行作为请求的结尾。
GET /test.htm HTTP/1.1
Accept]: image/gif, image/jpeg, */* User
selling agent: Mozilla/4.0
Host: 192.168.0.1
Listing 1.A: HTTP GET-request
HTTP/1.1 200 OK
Date: Mon, 06 Dec 1999 20:55:12 GMT Server:
Apache/1.3.6 (Linux)
Content-length: 82
Content-type: text/html
Test-Seite
Listing 1.B: HTTP response as result of the GET-request from listing 1.A
作为对HTTP请求的回答主要由两部分组成。首先有一个个别文本行的标题。跟着又一个内容对象（可选择）。这个内容对象大概由一些文本行组成，假设是一个HTML文件或者二进制文件，这时候可以传送GIF或JPEG格式的图像。标题的第一行特别重要。它起着报告状态和错误信息的作用。如果发生错误，只传送标题或标题的一部分作为回答。
2．网络服务器的功能原理
简单化一个网络服务器可以被设想成像一个特殊类型的文件服务器。Picture 2.A展示出了总体结构。网络服务器从网络浏览器接收了一个HTTP的GET请求。通过这个请求，必须有一个明确的文件作为回答（见Picture 2.A中的Step1）。之后，网络服务器尝试进入被请求电脑的文件系统。然后尝试找到一个需要的文件（Step2）。在成功搜寻之后，网络服务器读取整个文件（Step3），作为一个回答传送回网络浏览器（HTTP响应由标题和内容对象组成）。如果网络服务器不能在文件系统中找到合适的文件，一个错误信息（只包含标题的HTTP响应）简单地作为响应发送到客户端。
Figure 2: Functional principle from Web server and browser
网络的内容由单独的文件构建。它的基础是用HTML页的静态文件构建的。在这些HTML文件里涉及到远程文件的嵌入。这些文件是GIF或JPEG格式的这些有代表性地图片。然而也涉及到其它一些对象，例如可能有JAVA程序。在网络浏览器接收到网络服务器的HTML文件之后，这个文件将被评价然后为外部参考搜索。现在Picture 2.A的1－4步将为每一个外部参考再一次运行，为了从相应的网络服务器中请求各自的文件。请注意，这样一个参考由网络服务器的名字或IP地址组成（例如“https://www.doczj.com/doc/8e8322778.html,”），需要文件的名字也是如此（例如“picture1.gif”）。所以事实上每一个参考都能够查阅另一个服务器。换句话说，一个HTML文件能够定位在服务器“ssv －embedded.de”上，但通过这个HTML文件外部涉及到的需要的图像定位在网络服务器“https://www.doczj.com/doc/8e8322778.html,”上。最后这个分离对象的网络是万维网（WWW）得名的原因。所有通过网络服务器的必须得文件被浏览器请求，就像Picture 2.A中展示的那样。通常这些文件被存储在网络服务器的文件系统中，网络管理员有时会更新它们。
网络服务器更进一步的基本功能是我们前面提到的公共网关接口（CGI－Common Gateway Interface , 公共网关接口）。最初这项技术只应用于简单的嵌入HTML页的窗体。作为窗体填料结果的数据将经HTTP－GET或POST－request被传送到网络服务器（见Picture 2.B的Step1）。在这样一个GET－或POST－的请求中，CGI需要被窗体赋值的程序名已经被包括进去。这个程序需要放在网络服务器上。通常存储在“/cgi－bin”目录中。
GET－或POST－请求的结果是网络服务器启动位于“/cgi－bin”目录中的CGI程序，根据参数传递标准的数据（Step2）。一个CGI程序的输出导向到网络服务器（Step3）。然后网络服务器把数据全部传送到网络浏览器作为响应（Step4）。
3．动态产生HTML页
与一个公司通过静态页面和图片告诉人们有关产品计划和服务的网页相反，一个嵌入式的网
络服务器能够提供动态产生的内容。它将在首先通过浏览器进入的时候产生动态页面。如何另外通过Internet检查系统的实际温度？静态HTML文件对一个嵌入式的网络服务器来说没有什么意思。最多关于固件的版本和服务的信息是通过HTML格式存储的。另外所有其它的任务通常都是由动态产生HTML完成的。
在请求的时刻有两种产生HTML页的不同技术：第一种是所谓的服务器方脚本，第二种是CGI 设计。在服务器方脚本中，脚本代码嵌入到HTML页中。如果需要，这些代码将在服务器方被执行。
因此，有许多种可以提供的脚本语言，这些语言在HTML页中都可用。在Linux团体中主要使用PHP（PHP：一种新型的CGI网络程序编写语言。）。微软中意的是VBScript。在HTML页中插入JAVA同样可能。美国的Sun公司将这种技术命名为JSP。用脚本代码编写的网页静态地存储在网络服务器的文件系统之中。在服务器的文件被传送到客户端之前，一段特殊的程序用动态产生的标准HTML取代整个脚本代码。而网络浏览器在脚本语言中将什么也看不到。
Figure 3: Single steps of the Server-Side-Scripting
Picture 3展示了服务器方脚本的简单步骤。第一步中网络浏览器经HTTP的GET－request 请求一个明确的HTML文件。网络服务器认可需要文件的明确的扩展名（例如用*.ASP或*.PHP代替*.HTM或*.HTML），然后启动一个脚本引擎（见Step2）。这段程序得到需要的包括文件系统得到的脚本代码在内的HTML文件（Step3），执行脚本代码，制造一个新的不用脚本代码的HTML文件（Step4）。包括的脚本代码将被动态产生的HTML所代替。这个新的HTML文件将被网络服务器读入（Step5），然后发送给网络浏览器（Step6）。如果服务器方脚本被期望用于嵌入式网络服务器，那么你不得不考虑必要的附加资源。一个简单的例子：为了执行在一个网页中嵌入PHP代码，必须为服务器附加程序模块。一个脚本引擎和嵌入式网络服务器被存储在嵌入式系统的闪存芯片中。有了这些，执行期间需要更多的内存。
4．Linux下网络服务器的运行
一旦谈起关于网络服务器在和Linux连接中的问题，大部分人马上想到了Apache。在Netcraft Survey的调查之后，全世界的网络服务器主要使用了这种程序。Apache是对传说中的NCSA服务器的增进。Apache（Apache－美洲印第安人的一种族）的名字与印第安人无关。它是从“A Patchy Server”构造而来，因为第一个版本由不同的代码和补丁文件装配起来。
此外还有许多其它的网络服务器——甚至是对于Linux的。这些服务器的大多数固定在GPL （类似Apache）之下，可以免费使用。更为广泛的内容可以参见“http：//https://www.doczj.com/doc/8e8322778.html,/”。每一个网络服务器都有其优缺点。一些拥有明确的功能和特殊的性质；一些对同时发生的请求通过它们的反应速度达到最好的辨别，像它们对配置设定的变化；另外一些设计用于需要最小的资源和提供非常小的设置可能性，像只有一个客户的连接。
对一个嵌入式网络服务器来说最重要的事情是实际资源的需求。有时嵌入式系统只提供最小的资源，主要与Linux共享。其间有许多高性能的32位386/486微控制器或基于ARM的拥有8M RAM和2M Flash－ROM的嵌入式系统（Picture 4）。从这个ROM（只读存储器，例如闪存芯片）将被导入一个完全的Linux，它基于2.2或2.4的内核，有TCP/IP协议层和网络服务器。HTML 页和程序同样存在ROM中用来产生网页。一个嵌入式系统的空间需求与一张小的大邮票相似。很好理解它没有位置给一个像Apache一样强大的网络服务器。
Figure 4: Embedded Web Server Module with StrongARM and Linux
一个Apache的容量几乎同样如此。它不需要通过网络服务器和浏览器形象化一个影印机的计数器或一个过滤器的状态。在许多情况下一个单一的网络服务器就足够了。两个典型的代表是boa（https://www.doczj.com/doc/8e8322778.html,）和thttpd（https://www.doczj.com/doc/8e8322778.html,）。起初，两个网络服务器都用于和运行在Linux下的嵌入式系统连接。boa和thttpd的结构设置比较简陋，但却足够了。顺便说一下，它们的源代码对用户是开放的。这些服务器上可执行的二进制文件总是小于80k，能够没有问题的整合到大多数嵌入式系统中。对于网页的动态产生，两个服务器都只提供了CGI作为增补。更高的技术，像SSI则没有提供。
嵌入式网络服务器和Apache很大的差别在于，相对有限构造设置，同时发生请求数量的最大可能。高性能的服务器像Apache立即为每一个引入的客户端请求制造一个自己的过程。在这个过程里所有进一步的步骤都将被执行。这需要在运行期间拥有一个非常好的规划和大量的空余内存资源。但是另一方面，许多网络浏览器能够同时进入这样一个网络服务器中。嵌入式网络服务器像boa和thttpd只工作于一个单一的过程。如果两个用户同时需要进入一个嵌入式网络服务器，其中之一则不得不等待片刻。但是在嵌入式系统的环境中这是完全有理由的。这种情况首先是一个远程保持、远程配置和相似任务的问题。想来也不会有那么多同时的请求吧。
图的明细表：
图一：TCP/IP层和HTTP设计模型
图二：来自网络服务器和浏览器的功能原理
图三：服务器方脚本的单步
图四：以强大的ARM和Linux的嵌入式网络服务器
清单列表：
1．A：HTTP的GET请求
1．B：HTTP对来自1.A的GET请求的响应
利用嵌入式Linux的数字集成逻辑（DIL）/网络计算机（NetPCs）DNP/1110
人工神经网络原理及实际应用 摘要：本文就主要讲述一下神经网络的基本原理，特别是BP神经网络原理，以及它在实际工程中的应用。 关键词：神经网络、BP算法、鲁棒自适应控制、Smith－PID 本世纪初，科学家们就一直探究大脑构筑函数和思维运行机理。特别是近二十年来。对大脑有关的感觉器官的仿生做了不少工作，人脑含有数亿个神经元，并以特殊的复杂形式组成在一起，它能够在“计算＂某些问题（如难以用数学描述或非确定性问题等）时，比目前最快的计算机还要快许多倍。大脑的信号传导速度要比电子元件的信号传导要慢百万倍，然而，大脑的信息处理速度比电子元件的处理速度快许多倍，因此科学家推测大脑的信息处理方式和思维方式是非常复杂的，是一个复杂并行信息处理系统。1943年Macullocu和Pitts融合了生物物理学和数学提出了第一个神经元模型。从这以后，人工神经网络经历了发展，停滞，再发展的过程，时至今日发展正走向成熟，在广泛领域得到了令人鼓舞的应用成果。本文就主要讲述一下神经网络的原理，特别是BP神经网络原理，以及它在实际中的应用。 1.神经网络的基本原理 因为人工神经网络是模拟人和动物的神经网络的某种结构和功能的模拟，所以要了解神经网络的工作原理，所以我们首先要了解生物神经元。其结构如下图所示： 从上图可看出生物神经元它包括，细胞体：由细胞核、细胞质与细胞膜组成；
轴突：是从细胞体向外伸出的细长部分，也就是神经纤维。轴突是神经细胞的输出端，通过它向外传出神经冲动；树突：是细胞体向外伸出的许多较短的树枝状分支。它们是细胞的输入端，接受来自其它神经元的冲动；突触：神经元之间相互连接的地方，既是神经末梢与树突相接触的交界面。 对于从同一树突先后传入的神经冲动，以及同一时间从不同树突输入的神经冲动，神经细胞均可加以综合处理，处理的结果可使细胞膜电位升高；当膜电位升高到一阀值（约40mV），细胞进入兴奋状态，产生神经冲动，并由轴突输出神经冲动；当输入的冲动减小，综合处理的结果使膜电位下降，当下降到阀值时。细胞进入抑制状态，此时无神经冲动输出。“兴奋”和“抑制”，神经细胞必呈其一。 突触界面具有脉冲/电位信号转换功能，即类似于D/A转换功能。沿轴突和树突传递的是等幅、恒宽、编码的离散电脉冲信号。细胞中膜电位是连续的模拟量。 神经冲动信号的传导速度在1～150m/s之间，随纤维的粗细，髓鞘的有无而不同。 神经细胞的重要特点是具有学习功能并有遗忘和疲劳效应。总之，随着对生物神经元的深入研究，揭示出神经元不是简单的双稳逻辑元件而是微型生物信息处理机制和控制机。 而神经网络的基本原理也就是对生物神经元进行尽可能的模拟，当然，以目前的理论水平，制造水平，和应用水平，还与人脑神经网络的有着很大的差别，它只是对人脑神经网络有选择的，单一的，简化的构造和性能模拟，从而形成了不同功能的，多种类型的，不同层次的神经网络模型。 2.BP神经网络 目前，再这一基本原理上已发展了几十种神经网络，例如Hopficld模型，Feldmann等的连接型网络模型，Hinton等的玻尔茨曼机模型，以及Rumelhart 等的多层感知机模型和Kohonen的自组织网络模型等等。在这众多神经网络模型中，应用最广泛的是多层感知机神经网络。 这里我们重点的讲述一下BP神经网络。多层感知机神经网络的研究始于50年代，但一直进展不大。直到1985年，Rumelhart等人提出了误差反向传递学习算法（即BP算），实现了Minsky的多层网络设想，其网络模型如下图所示。它可以分为输入层，影层（也叫中间层），和输出层，其中中间层可以是一层，也可以多层，看实际情况而定。
开题报告如何写 注意点 １.一、对指导教师下达的课题任务的学习与理解 这部分主要是阐述做本课题的重要意义 ２.二、阅读文献资料进行调研的综述 这部分就是对课题相关的研究的综述落脚于本课题解决了那些关键问题 3．三、根据任务书的任务及文件调研结果，初步拟定执行实施的方案(含具体进度计划) 这部分重点写具体实现的技术路线方案的具体实施方法和步骤了，具体进度计划只是附在后面的东西不是重点
南京邮电大学通达学院毕业设计(论文）开题报告
文献[5] 基于信息数据分析的微博研究综述[J]；研究微博信息数据的分析,在这类研究中，大多数以微博消息传播的三大构件---微博消息、用户、用户关系为研究对象。以微博消息传播和微博成员组织为主要研究内容,目的在于发祥微博中用户、消息传博、热点话题、用户关系网络等的规律。基于微博信息数据分析的研究近年来在国内外都取得了很多成果，掌握了微博中的大量特征。该文献从微博消息传播三大构件的角度，对当前基于信息数据分析的微博研究进行系统梳理，提出微博信息传播三大构件的概念,归纳了此类研究的主要研究内容及方法。 对于大多用户提出的与主题或领域相关的查询需求，传统的通用搜索引擎往往不能提供令人满意的结果网页。为了克服通用搜索引擎的以上不足,提出了面向主题的聚焦爬虫的研究。文献[６]综述了聚焦爬虫技术的研究。其中介绍并分析了聚焦爬虫中的关键技术：抓取目标定义与描述，网页分析算法和网页分析策略，并根据网络拓扑、网页数据内容、用户行为等方面将各种网页分析算法做了分类和比较。聚焦爬虫能够克服通用爬虫的不足之处。 文献[７]首先介绍了网络爬虫工作原理，传统网络爬虫的实现过程，并对网络爬虫中使用的关键技术进行了研究,包括网页搜索策略、URＬ去重算法、网页分析技术、更新策略等。然后针对微博的特点和Ajaｘ技术的实现方法,指出传统网络爬虫的不足,以及信息抓取的技术难点,深入分析了现有的基于Ａjaｘ的网络爬虫的最新技术——通过模拟浏览器行为,触发JavaScript事件（如cｌiｃk, oｎmｏuseo ｖer等)，解析JavａSｃripｔ脚本，动态更新网页DOＭ树，抽取网页中的有效信息。最后,详细论述了面向ＳNS网络爬虫系统的设计方案，整体构架,以及各功能模块的具体实现。面向微博的网络爬虫系统的实现是以新浪微博作为抓取的目标网站。结合新浪微博网页的特点,通过模拟用户行为,解析JavaSc ｒipt,建立DＯＭ树来获取网页动态信息,并按照一定的规则提取出网页中的URL和有效信息，并将有效信息存入数据库。本系统成功的实现了基于Ajax技术的网页信息的提取。 文献[８］引入网页页面分析技术和主题相关性分析技术,解决各大网站微博相继提供了抓取微博的AＰI，这些APＩ都有访问次数的限制，无法满足获取大量微博数据的要求,同时抓取的数据往往很杂乱的问题。展开基于主题的微博网页爬虫的研究与设计。本文的主要工作有研究分析网页页面分析技术，根据微博页面特点选择微博页面信息获取方法；重点描述基于“剪枝”的广度优先搜索策略的思考以及设计的详细过程，着重解决URL的去重、ＵRL地址集合动态变化等问题;研究分析短文本主题抽取技术以及多关键匹配技术,确定微博主题相关性分析的设计方案；最后设计实现基于主题的微博网页爬虫的原型系统,实时抓取和存储微博数据。本文研究的核心问题是,根据微博数据的特点设计一种基于“剪枝”的广度优先搜索策略,并将其应用到微博爬虫中；同时使用微博页面分析技术使得爬虫不受微博平台API限制,从而让用户尽可能准确地抓取主题相关的微博数据。通过多次反复实验获取原型系统实验结果，将实验结果同基于APＩ微博爬虫和基于网页微博爬虫的抓取效果进行对比分析得出结论:本文提出的爬行策略能够抓取主题相关的微博数据,虽然在效率上有所降低,但在抓取的微博数据具有较好的主题相关性。这实验结果证明本论文研究的实现方案是可行的。 文献[９]阐述了基于ajax的web应用程序的爬虫和用户界面状态改变的动态分析的过程和思路。文献[10]对于全球社交网络Twｉtter,设计并实现了,一个爬虫系统,从另一个角度阐明了Pｙtｈon在编写爬虫这个方面的强大和快速。仅仅用少量的代码就能实现爬虫系统，并且再强大的社交网站也可
Microcomputer Systems Electronic systems are used for handing information in the most general sense; this information may be telephone conversation, instrument read or a company’s accounts, but in each case the same main type of operation are involved: the processing, storage and transmission of information. in conventional electronic design these operations are combined at the function level; for example a counter, whether electronic or mechanical, stores the current and increments it by one as required. A system such as an electronic clock which employs counters has its storage and processing capabilities spread throughout the system because each counter is able to store and process numbers. Present day microprocessor based systems depart from this conventional approach by separating the three functions of processing, storage, and transmission into different section of the system. This partitioning into three main functions was devised by Von Neumann during the 1940s, and was not conceived especially for microcomputers. Almost every computer ever made has been designed with this structure, and despite the enormous range in their physical forms, they have all been of essentially the same basic design. In a microprocessor based system the processing will be performed in the microprocessor itself. The storage will be by means of memory circuits and the communication of information into and out of the system will be by means of special input/output(I/O) circuits. It would be impossible to identify a particular piece of hardware which performed the counting in a microprocessor based clock because the time would be stored in the memory and incremented at regular intervals but the microprocessor. However, the software which defined the system’s behavior would contain sections that performed as counters. The apparently rather abstract approach to the architecture of the microprocessor and its associated circuits allows it to be very flexible in use, since the system is defined almost entirely software. The design process is largely one of software engineering, and the similar problems of construction and maintenance which occur in conventional engineering are encountered when producing software. The figure1.1 illustrates how these three sections within a microcomputer are connected in terms of the communication of information within the machine. The system is controlled by the microprocessor which supervises the transfer of information between itself and the memory and input/output sections. The external connections relate to the rest (that is, the non-computer part) of
计算机网络安全综述学生姓名：李嘉伟 学号：11209080279 院系：信息工程学院指导教师姓名：夏峰二零一三年十月
［摘要］ 随着计算机网络技术的快速发展，网络安全日益成为人们关注的焦点。本文分析了影响网络安全的主要因素及攻击的主要方式，从管理和技术两方面就加强计算机网络安全提出了针对性的建议。 ［关键词］ 计算机网络；安全；管理；技术；加密；防火墙 一．引言 计算机网络是一个开放和自由的空间，但公开化的网络平台为非法入侵者提供了可乘之机，黑客和反黑客、破坏和反破坏的斗争愈演愈烈，不仅影响了网络稳定运行和用户的正常使用，造成重大经济损失，而且还可能威胁到国家安全。如何更有效地保护重要的信息数据、提高计算机网络的安全性已经成为影响一个国家的政治、经济、军事和人民生活的重大关键问题。本文通过深入分析网络安全面临的挑战及攻击的主要方式，从管理和技术两方面就加强计算机网络安全提出针对性建议。
二．正文 1.影响网络安全的主要因素［1］ 计算机网络安全是指“为数据处理系统建立和采取的技术和管理的安全保护，保护计算机硬件、软件数据不因偶然和恶意的原因而遭到破坏、更改和泄漏”。计算机网络所面临的威胁是多方面的，既包括对网络中信息的威胁，也包括对网络中设备的威胁，但归结起来，主要有三点：一是人为的无意失误。如操作员安全配置不当造成系统存在安全漏洞，用户安全意识不强，口令选择不慎，将自己的帐号随意转借他人或与别人共享等都会给网络安全带来威胁。二是人为的恶意攻击。这也是目前计算机网络所面临的最大威胁，比如敌手的攻击和计算机犯罪都属于这种情况，此类攻击又可以分为两种：一种是主动攻击，它以各种方式有选择地破坏信息的有效性和完整性；另一类是被动攻击，它是在不影响网络正常工作的情况下，进行截获、窃取、破译以获得重要机密信息。这两种攻击均可对计算机网络造成极大的危害，并导致机密数据的泄漏。三是网络软件的漏洞和“后门”。任何一款软件都或多或少存在漏洞，这些缺陷和漏洞恰恰就是黑客进行攻击的首选目标。绝大部分网络入侵事件都是因为安全措施不完善，没有及时补上系统漏洞造成的。此外，软件公司的编程人员为便于维护而设置的软件“后门”也是不容忽视的巨大威胁，一旦“后门”洞开，别人就能随意进入系统，后果不堪设想。
、外文资料 License Plate Recognition Based On Prior Knowledge Abstract - In this paper, a new algorithm based on improved BP (back propagation) neural network for Chinese vehicle license plate recognition (LPR) is described. The proposed approach provides a solution for the vehicle license plates (VLP) which were degraded severely. What it remarkably differs from the traditional methods is the application of prior knowledge of license plate to the procedure of location, segmentation and recognition. Color collocation is used to locate the license plate in the image. Dimensions of each character are constant, which is used to segment the character of VLPs. The Layout of the Chinese VLP is an important feature, which is used to construct a classifier for recognizing. The experimental results show that the improved algorithm is effective under the condition that the license plates were degraded severely. Index Terms - License plate recognition, prior knowledge, vehicle license plates, neural network. I. INTRODUCTION Vehicle License-Plate (VLP) recognition is a very interesting but difficult problem. It is important in a number of applications such as weight-and-speed-limit, red traffic infringement, road surveys and park security [1]. VLP recognition system consists of the plate location, the characters segmentation, and the characters recognition. These tasks become more sophisticated when dealing with plate images taken in various inclined angles or under various lighting, weather condition and cleanliness of the plate. Because this problem is usually used in real-time systems, it requires not only accuracy but also fast processing. Most existing VLP recognition methods [2], [3], [4], [5] reduce the complexity and increase the recognition rate by using some specific features of local VLPs and establishing some constrains on the position, distance from the camera to vehicles, and the inclined angles. In addition, neural network was used to increase the recognition rate [6], [7] but the traditional recognition methods seldom consider the prior knowledge of the local VLPs. In this paper, we proposed a new improved learning method of BP algorithm based on specific features of Chinese VLPs. The proposed algorithm overcomes the low speed convergence of BP neural network [8] and remarkable increases the recognition rate especially under the condition that the license plate images were degrade severely.
人工神经网络的发展与应用 神经网络发展 启蒙时期 启蒙时期开始于1980年美国著名心理学家W．James关于人脑结构与功能的研究，结束于1969年Minsky和Pape~发表的《感知器》(Perceptron)一书。早在1943年，心理学家McCulloch和数学家Pitts合作提出了形式神经元的数学模型(即M—P模型)，该模型把神经细胞的动作描述为：1神经元的活动表现为兴奋或抑制的二值变化；2任何兴奋性突触有输入激励后，使神经元兴奋与神经元先前的动作状态无关；3任何抑制性突触有输入激励后，使神经元抑制；4突触的值不随时间改变；5突触从感知输入到传送出一个输出脉冲的延迟时问是0．5ms。可见，M—P模型是用逻辑的数学工具研究客观世界的事件在形式神经网络中的表述。现在来看M—P 模型尽管过于简单，而且其观点也并非完全正确，但是其理论有一定的贡献。因此，M—P模型被认为开创了神经科学理论研究的新时代。1949年，心理学家D．0．Hebb 提出了神经元之间突触联系强度可变的假设，并据此提出神经元的学习规则——Hebb规则，为神经网络的学习算法奠定了基础。1957年，计算机学家FrankRosenblatt提出了一种具有三层网络特性的神经网络结构，称为“感知器”(Perceptron)，它是由阈值性神经元组成，试图模拟动物和人脑的感知学习能力，Rosenblatt认为信息被包含在相互连接或联合之中，而不是反映在拓扑结构的表示法中；另外，对于如何存储影响认知和行为的信息问题，他认为，存储的信息在神经网络系统内开始形成新的连接或传递链路后，新 的刺激将会通过这些新建立的链路自动地激活适当的响应部分，而不是要求任何识别或坚定他们的过程。1962年Widrow提出了自适应线性元件(Ada—line)，它是连续取值的线性网络，主要用于自适应信号处理和自适应控制。 低潮期 人工智能的创始人之一Minkey和pape~经过数年研究，对以感知器为代表的网络系统的功能及其局限性从数学上做了深入的研究，于1969年出版了很有影响的《Perceptron)一书，该书提出了感知器不可能实现复杂的逻辑函数，这对当时的人工神经网络研究产生了极大的负面影响，从而使神经网络研究处于低潮时期。引起低潮的更重要的原因是：20世纪7O年代以来集成电路和微电子技术的迅猛发展，使传统的冯·诺伊曼型计算机进入发展的全盛时期，因此暂时掩盖了发展新型计算机和寻求新的神经网络的必要性和迫切性。但是在此时期，波士顿大学的S．Grossberg教授和赫尔辛基大学的Koho—nen教授，仍致力于神经网络的研究，分别提出了自适应共振理论(Adaptive Resonance Theory)和自组织特征映射模型(SOM)。以上开创性的研究成果和工作虽然未能引起当时人们的普遍重视，但其科学价值却不可磨灭，它们为神经网络的进一步发展奠定了基础。 复兴时期 20世纪80年代以来，由于以逻辑推理为基础的人工智能理论和冯·诺伊曼型计算机在处理诸如视觉、听觉、联想记忆等智能信息处理问题上受到挫折，促使人们
外文资料 ABSTRACT Crawling the web is deceptively simple: the basic algorithm is (a)Fetch a page (b) Parse it to extract all linked URLs (c) For all the URLs not seen before, repeat (a)–(c). However, the size of the web (estimated at over 4 billion pages) and its rate of change (estimated at 7% per week) move this plan from a trivial programming exercise to a serious algorithmic and system design challenge. Indeed, these two factors alone imply that for a reasonably fresh and complete crawl of the web, step (a) must be executed about a thousand times per second, and thus the membership test (c) must be done well over ten thousand times per second against a set too large to store in main memory. This requires a distributed architecture, which further complicates the membership test. A crucial way to speed up the test is to cache, that is, to store in main memory a (dynamic) subset of the “seen” URLs. The main goal of this paper is to carefully investigate several URL caching techniques for web crawling. We consider both practical algorithms: random replacement, static cache, LRU, and CLOCK, and theoretical limits: clairvoyant caching and infinite cache. We performed about 1,800 simulations using these algorithms with various cache sizes, using actual log data extracted from a massive 33 day web crawl that issued over one billion HTTP requests. Our main conclusion is that caching is very effective – in our setup, a cache of roughly 50,000 entries can achieve a hit rate of almost 80%. Interestingly, this cache size falls at a critical point: a substantially smaller cache is much less effective while a substantially larger cache brings little additional benefit. We conjecture that such critical points are inherent to our problem and venture an explanation for this phenomenon. 1. INTRODUCTION A recent Pew Foundation study [31] states that “Search eng ines have become an indispensable utility for Internet users” and estimates that as of mid-2002, slightly
外文文献资料 Distributed Temperature Sensor 1.Sensor introduction 1.1 Temperature sensor background In the human living environment, temperature playing an extremely important role。No matter where you live, engaged in any work, ever-present dealt with temperature under. Since the 18th century, industry since the industrial revolution to whether can master send exhibition has the absolute temperature touch. In metallurgy, steel, petrochemical, cement, glass, medicine industry and so on, can say almost eighty percent of industrial departments have to consider the factors with temperature. Temperature for industrial so important, thus promoting the development of the temperature sensor. 1.2 Temperature sensor development Major general through three sensor development phase: analog integrated temperature sensor. The sensor is taken with silicon semiconductor integrated workmanship, therefore also called silicon sensor or monolithic integrated temperature sensor. Such sensing instruments have single function (only measuring temperature), temperature measurement error is smaller, price low, fast response, the transmission distance, small volume, micro-consumption electronic etc, suitable for long distance measurement temperature, temperature control, do not need to undertake nonlinear calibration, peripheral circuit is simple. It is currently the most common application at home and abroad, an integrated sensor。Typical products have AD590 AD592, TMP17, LM135, etc.jAnalog integrated temperature controller. Analog integrated temperature controller mainly include temperature control switch, programmable temperature controller, a typical product have LM56, AD22105 and MAX6509. Some increase strength type integrated temperature controller (for example TC652/653) also contains the A/D converter and cure good sequence, this process with the intelligent temperature sensor some similarities. But it is not its system, work by micro processing device control, this is the main difference between. Intelligent temperature sensor. intelligent temperature sensor (also called digital temperature degrees sensor) is in the mid 1990s launch. It is microelectronics technology, computer technology and the dynamic testing technology (ATE) crystallization. Intelligent temperature sensor internal contain temperature sensor, A/D converter, signal processor,
网络安全外文翻译文献 (文档含英文原文和中文翻译) 翻译： 计算机网络安全与防范 1.1引言 计算机技术的飞速发展提供了一定的技术保障，这意味着计算机应用已经渗透到社会的各个领域。在同一时间，巨大的进步和网络技术的普及，社会带来了巨大的经济利润。然而，在破坏和攻击计算机信息系统的方法已经改变了很多的网络环境下，网络安全问题逐渐成为计算机安全的主流。
1.2网络安全 1.2.1计算机网络安全的概念和特点 计算机网络的安全性被认为是一个综合性的课题，由不同的人，包括计算机科学、网络技术、通讯技术、信息安全技术、应用数学、信息理论组成。作为一个系统性的概念，网络的安全性由物理安全、软件安全、信息安全和流通安全组成。从本质上讲，网络安全是指互联网信息安全。一般来说，安全性、集成性、可用性、可控性是关系到网络信息的相关理论和技术，属于计算机网络安全的研究领域。相反，狭隘“网络信息安全”是指网络安全，这是指保护信息秘密和集成，使用窃听、伪装、欺骗和篡夺系统的安全性漏洞等手段，避免非法活动的相关信息的安全性。总之，我们可以保护用户利益和验证用户的隐私。 计算机网络安全有保密性、完整性、真实性、可靠性、可用性、非抵赖性和可控性的特点。 隐私是指网络信息不会被泄露给非授权用户、实体或程序，但是授权的用户除外，例如，电子邮件仅仅是由收件人打开，其他任何人都不允许私自这样做。隐私通过网络信息传输时，需要得到安全保证。积极的解决方案可能会加密管理信息。虽然可以拦截，但它只是没有任何重要意义的乱码。 完整性是指网络信息可以保持不被修改、破坏，并在存储和传输过程中丢失。诚信保证网络的真实性，这意味着如果信息是由第三方或未经授权的人检查，内容仍然是真实的和没有被改变的。因此保持完整性是信息安全的基本要求。 可靠性信息的真实性主要是确认信息所有者和发件人的身份。 可靠性表明该系统能够在规定的时间和条件下完成相关的功能。这是所有的网络信息系统的建立和运作的基本目标。 可用性表明网络信息可被授权实体访问，并根据自己的需求使用。 不可抵赖性要求所有参加者不能否认或推翻成品的操作和在信息传输过程中的承诺。
英文文献 英文资料： Artificial neural networks (ANNs) to ArtificialNeuralNetworks, abbreviations also referred to as the neural network (NNs) or called connection model (ConnectionistModel), it is a kind of model animals neural network behavior characteristic, distributed parallel information processing algorithm mathematical model. This network rely on the complexity of the system, through the adjustment of mutual connection between nodes internal relations, so as to achieve the purpose of processing information. Artificial neural network has since learning and adaptive ability, can provide in advance of a batch of through mutual correspond of the input/output data, analyze master the law of potential between, according to the final rule, with a new input data to calculate, this study analyzed the output of the process is called the "training". Artificial neural network is made of a number of nonlinear interconnected processing unit, adaptive information processing system. It is in the modern neuroscience research results is proposed on the basis of, trying to simulate brain neural network processing, memory information way information processing. Artificial neural network has four basic characteristics: (1) the nonlinear relationship is the nature of the nonlinear common characteristics. The wisdom of the brain is a kind of non-linear phenomena. Artificial neurons in the activation or inhibit the two different state, this kind of behavior in mathematics performance for a nonlinear relationship. Has the threshold of neurons in the network formed by the has better properties, can improve the fault tolerance and storage capacity. (2) the limitations a neural network by DuoGe neurons widely usually connected to. A system of the overall behavior depends not only on the characteristics of single neurons, and may mainly by the unit the interaction between the, connected to the. Through a large number of connection between units simulation of the brain limitations. Associative memory is a typical example of limitations. (3) very qualitative artificial neural network is adaptive, self-organizing, learning ability. Neural network not only handling information can have all sorts of change, and in the treatment of the information at the same time, the nonlinear dynamic system itself is changing. Often by iterative process description of the power system evolution. (4) the convexity a system evolution direction, in certain conditions will depend on a particular state function. For example energy function, it is corresponding to the extreme value of the system stable state. The convexity refers to the function extreme value, it has DuoGe DuoGe system has a stable equilibrium state, this will cause the system to the diversity of evolution. Artificial neural network, the unit can mean different neurons process of the object, such as characteristics, letters, concept, or some meaningful abstract model. The type of network processing unit is divided into three categories: input unit, output unit and hidden units. Input unit accept outside the world of signal and data; Output unit of output system processing results; Hidden unit is in input and output unit, not between by external observation unit. The system The connections between neurons right value reflect the connection between the unit strength, information processing and embodied in the network said the processing unit in the connections. Artificial neural network is a kind of the procedures, and adaptability, brain style of information processing, its essence is through the network of transformation and dynamic behaviors have a