Search engine is a very useful tool, every Internet search material of use, because really convenient, do not need you own a a through, it would put you need to find out in front of you.

The source of the search engine very interesting also, it came from the traditional information retrieval theory, in which the full computer program through the scanning each article published in every word, and establish a word for the sort of the document retrieval unit, according to the word in the retrieval procedure in each article the frequency of the occurrence and every retrieval words in an article in the probability of to appear, containing these search term paper to sort the output of sorting results. Early in the Internet search engine is the address of the server resources collected, and the resources provided by the type of different and into different directory, again layer by layer classification. People Lenovo G430 battery want to find the information they want can be classified according to their layers into, you can finally get to its destination, find the information you want. This is actually the most primitive way, only apply to Internet information is not much. As the Internet information according to the geometrical type growth, the emergence of a real sense of search engine, these search engines know web site each page start, after on the Internet search with all the links, the representative super link all words put into a database. This is now the prototype of the search engine. Now the search engine has the simple search web pages of information, they have become more integrated, the beautification. To search engine authority Yahoo. For example, from March 1995 by African American China such as jerry Yang created Yahoo! Start, to now, they from a single search engine development up to now have the electronic commerce, news information service, an umbrella for free E-mail service, etc DuoZhong network service, fully explain the development of search engine from a single to integrated process.

The working principle of search engine can be divided into: # information gathering: search engine information gathering and basic it is automatic. Search engines use called web spiders automatic search robot program to even in a web page on the hyperlink. Robots on the page program chain of links to other pages, as in daily life had said “going, ten preach the…” From a few, like a page start, even to the database and all other web pages on the links. In theory, if the nets page have proper hyperlinks, robot can then traverse most web pages.

Arrange information: search engine of arrange information process known as “establish index”. Search engines should not only save the information collected, and according to certain rules them into line layout. Like a library catalog convenient search index. So, search engines don’t have to keep looking through it all the information can quickly find the material. Imagine if that information is not in any rules piles up at will in the search engine’s data in the library, then it every time looking for material all have to learn the entire database completely looking through again, so to fast computer system is useless.

Accept inquires to search engine users: issue queries, search engine accept inquires to users and information. Search engine every moment from heavy users of a few received the is also issued, it according to the inquires the requirements of each user to check their index, in a very short time the user needs to find the material, and returned to the user. At present, the search engine to return to main is given in the form of web link, through these links, users can be to contain their required data web pages. Usually in these links to search engine will provide a short from these HP dv6000 battery websites information in order to help users judge this page is not to the content, containing such through these simple can speed up the user’s speed of search.

See here, a lot of friends this said, as long as we will use good, don’t need to know that it’s the principle, tell us something about how to use the search engine. Should say, use network friend should use a search engine to find the material, but like for someone of the same, we can find newspaper, can find through the network, can also please professional people and come to find, but always have a best way, can make us the most convenient to find the fastest to that person, the use of the search engine is the same, how we can better use search engine? This is we want to give the key.

Search engine points several types, different ways to work, resulting in the information by the differences of the scope of cover. We usually only focus on a search a search engine is not wise, because it is a good search engines also have limitations, reasonable way should be root according to specific requirements choose different engines.

Our daily information needs can be roughly divided into two kinds, one kind is looking for reference material, and the other is the product or service for Chad, then the corresponding search engine choice should be full text search engines and directories index. Why? Because in the former demand for the target with very body, and directory index entries contain links of limited information, not meet our requirements, so full text search engine will naturally became our choice. Full text search index according to the work principle of qing, it from web pages extract all the information in words, so matching the scope of the search terms is much, also can satisfy even the most ill-advised information needs. That is why now most directory is adopted by the other full text indexing search engines provide level 2 web search reason.

If, on the other hand, we are looking for a product or service, then directory is the dominant index slightly. Because the site in submit directory index are required to provide site title and tracing above, and limit count, so the website owner will use the most concise language summary of your own business scope, let people seem to be clear at a glance. And most full text search engine directly extract nets page title and text as the links of the title and description. Full text search engine used the people have such experience, is the search results show that information are often too cluttered, let a person without method to figure out the web site at a glance of nature. Just us, although we is Google determined advocates, but in the search Dell 640M battery business information or use sohu, sina, often netease directory search. In addition, when you want to collect some sort of the web site, the directory indexed classified catalogue is your natural treasures.

Now, we commonly used several search engines is Google, Yahoo and the most big Chinese search engine baidu, and display the use of sogou songs. When exactly which to use search engine?

Know all kinds of search engines, analysis the characteristics of the needs of after you to determine what kind of search engines should make the most suitable for the search.

How to conduct a efficient search, a few very important skill: skills: learn to use one of two key words.

“China education and research computer network” of the overall construction goal is to make use of the advanced practical computer technology and network communication technology, the majority of higher school, promote connected these school campus network and information resources construction, and communication of the kingdom of existing international sex academic computer network interconnection, making it China’s entry into the world of higher school science and technology to the entrance of the quick and convenient. At the same time Lenovo Y510 battery develop a the world and the future high level talented person, improve the quality of teaching and the scientific research level of the most important infrastructure. In the conditions are ripe for other departments, provides the service, and with the domestic other computer network connected, and gradually form the computer network covering the whole country.

“China education and research computer network CERnet” is a including the national backbone network, area nets and campus network of level 3 levels of structure, network. The construction of the recent let including, in eight regional network connection of national backbone and international networking; The national network center; 8 regional network center and several area network; Function of complete network management system, to ensure the effective and reliable operation; Provide rich network resources and convenient application resource access method. “China education and research computer network” network center built in tsinghua university, area network center in Beijing, respectively in Shanghai, nanjing, xian, guangzhou, wuhan, chengdu, shenyang, eight of the city a famous university.

China education and research computer network has national coverage, and international and national computer network interconnection, so the method of Internet TCP/IP? Network system structure. China education and research computer network will make full use of the country has some public communication transmission was set, renting post and telecommunications departments digital data networks of DDN fiber optic cable line to form its backbone, and based on the using condition gradually improve the transmission rate.

China education and research computer network backbone node location choice considered universities and college students in countries distribution, communication infrastructure construction of specific conditions and geographical location, and other factors. Beijing, Shanghai, shenyang, guangzhou, wuhan, chengdu, nanjing, west Ann eight cities, is the backbone of the Chinese DDN ShuNiuJu and public utilities in China packet switching network and long distance telephone network node and, and, and, and consequently the institutions of higher learning and scientific research institutes are relatively concentrated area center, has good communication basic conditions and strong scientific research ability and level. So will set in the HP V6000 battery city the backbone node, and with the city as the center, building area network for the future, will build a nationwide CERnet education and research nets is beneficial,.

China education and research computer network network center is located at tsinghua university, through the nets network center, with international academic computer nets Internet network. The main network center position can include: network operation center; The network information center; High performance computing center and education training center and so on. China education and research computer network regional network the main function of the center is responsible for this area of the construction of network on things advisable. Area in university is the site of the center, responsible for the networking of college networking, and provides the technical support and service, also is the network management and all kinds of network application and service branch.

“China education and research computer network” gradually for the user to provide rich network should use resources. Including: email services; Web directory services; File access and Shared services; The science and technology information query service; Electronic news services; Information found services; Remote high speed information service and computing services; The remote computer education; The remote computer association with work; Education and scientific research management information service and so on.

“China education and research computer network” construction points in two stages. The first stage to the end of 1995, the backbone and international networking built, network center, area nets network center, network management system and basic network resources construction and application system, even the 100 or so of higher school access; The second stage from 1996 to 2000, built into the area network, connected to the majority of higher school into the net, provide more rich nets collaterals application resources.

Completed “China education and research computer network CERnet a demonstration project” is a including the national backbone, area nets and campus network of level 3 levels of structure, the computer network project. Its main technical contents include:

Built in 64 kbpsDDN line 8 regional network connection the national center of CERnet backbone, and with 128 KBPS international communication lines and Internet direct connection. The communication line rate can according to the need to upgrade;

Built in Beijing tsinghua university of CERnet national network center; Built respectively in Beijing, Shanghai, nanjing, xian, guangzhou, wuhan, chengdu, shenyang city, eight of the 10 universities 8 regional network center and the two main node. These regional network center and main node in addition to support the Dell M6300 battery operation of CERnet backbone outside this area, but also provide the institutions of higher learning networking services. In the relevant provinces and cities in the higher court help and support of the has made the area network development planning, and began to carry out; Built the function is more perfect CERnet network management system and safety system. Mainly includes: configuration management, failure management, security management, performance management and billing management function;

Built a batch of network resources and the application system, and has begun to provide services in the network;

CERnet using Internet TCP/IP network system structure and agreement technical standards. The national network center and the area network center in the world currently has the most advanced technology and the most complete function of network and computer equipment;

In the course of the construction of the CERnet, at all levels of network center is also a user’s education and collaterals nets training work, for promotion in China and popularization of the computer information network foundation knowledge and application to make positive contribution;

By the end of 1995, the higher colleges CERnet networking has reached more than 100 range, has covered except is Chinese Taiwan area, Hong Kong, Macao and the Tibetan autonomous region outside of all provinces, municipalities and autonomous regions, become at present China Internet connected with the biggest academic computer nets.

Different classification, is a description of the different characteristics.

(a) according to the network coverage classification

According to the geographical position classification, can be divided into computer network LAN and wan and intracity networks.

LAN generally in dozens of meters to thousands of meters, within the scope of a local area network can hold just a few or even thousands of computer.

LAN distributed in smaller geographic range. Because they use different transmission can force the transmission medium, so the transmission distance LAN is different also.

LAN are often used to a group of people, such as a company, a unit, a building, a school, etc.

Wan coverage range is very wide, across borders, can the state border, and even the world. Wan is the public portion of the network, China telecom department general wan. We adopt the ISDN, ADSL access the Internet, is actually access the wan.

Through the local area network technology, wan can realize local network of IBM X61t battery interconnected. Man city is limited in size a city within the scope of regional network. Metro nets speed faster than the wan, accord with broadband trend, so now is developing very quickly. And the bureau domain, compared with distributed (net geographical range, generally speaking, the characteristics of the metro nets coverage between 10 to 100 km between. But should in fact it is a man said in developing and changing the concept, especially the standardization of different groups to the definition of weave, man is not identical. But with the rise of the market and the deepening of the research is close to the understanding of the man, the industry also gradually have reached some consensus. Tell from the concept, intracity networks is a common set of network, in a city to provide access and services. Area In particular, intracity networks is a single, independent, and clear “city area network”, by a network operators, usually is a service provider or the telecommunication operation business have and operation.

(2) according to the network topology structure classification

The topology of the network is to point to in the network communication lines and site (for a machine or equipment is) mutual connection form of geometry. According to the different topology structure, can be divided into star will network to network, the annular network, main line network of three basic types. In the three types of network structure, can be based on a combination of nets, tree star nets, mesh network and other types of network topology.

Star network structure

In the network structure of various star computer use their cable connected to the network, so if a site out of the question, will not affect the operation of the network. Star type network structure is now the most commonly used network topology structure.

With loop network structure

The annular network structure of each site through a communications medium into a closed ring. Ring network is easy to install and monitor, but limited HP CQ40 battery capacity, after the completion of the network, it is difficult to add new site. Therefore, now has basically don’t use a LAN with loop network structure.

Lu main line network structure

In the main line network structure of all site sharing a data channels. Main line network installation is simple and convenient, need the shortest cable laying, low cost, a site generally will not affect the entire network fault, but medium fault can lead to paralysis of the network. Main line network safety monitoring is more difficult, low, increase the new site will not single star nets Jane. So, the main line network structure now basically has been eliminated.

(3) according to the classification of the transmission medium

According to the network transmission medium classification, computer network can be divided into cable network and wireless network two kinds. LAN usually USES a single transmission medium, and the man and the wan DuoZhong transmission medium.

Cable network

Cable network refers to using coaxial cable, twisted pair, optical fiber cable medium is the network connection machine project.

The twisted-pair cable network and is the most common way of networking. It cheap, convenient in Ann, but vulnerable to interference, transfer rate is low, the transmission distance than coaxial cable to short. Optical fiber network using optical fiber as transmission medium, the transmission distance long, transfer rate high, resistance to interfere with strong sex, now are developing rapidly.

Wireless network

Wireless network using microwave, infrared, such as radio electromagnetic Dell 1720 battery wave transmission medium, because as a wireless network networking mode flexibility, so it’s a very promising network mode. At present, many universities and companies have been using a wireless network.

(4) according to the service object classification

According to the network service object classification can be divided into enterprise network, nets, and campus network type etc.

Enterprise nets

Enterprise nets as the name suggests, is a enterprise service for the computer network. Enterprise nets can include LAN, may include part of the wan. And for a possession, and ideas by better in other place no branches, the formation of a local area network also can meet the need to.

Campus network

Campus network for college, high school, is the primary service network. As the round “officer officer is connected” project starting, there are more and more of the campus network, and now the whole nation has had five round many middle schools and primary schools have the campus network.

modem

Modem, Modem Modulator/Demodulator, namely the abbreviations.

In the early days of computer network, a modem is the most commonly used network access devices, it is the role of the computer links to telephone network.

The composition of the modem includes baseband processing, demodulation, amplification and filtering, balanced a few parts, etc.

Popularly say, modem the function of the one is put the computer in digital information can be transmitted to add in the telephone network of analog signals and instead of the process.

The modulation is the process of loading process, digital HP CQ45 battery signal demodulation is received from the mode of the signal to extract the digital signal process.

Note that the use of modem to pairing, also is your computer to through the-with a modem and another computer communication, if he must also take the computer have a modem.

Choose a modem is one of important index of the transmission rate per second, which is the transfer of digits, the unit is bit/s, abbreviations for BPS.

At present the main use of several communication rate is 14.4 KBPS, 28.8 KBPS, 33.6 KBPS and 56 KBPS modem.

Modem equipment in the form is the outer type, built-in, PC KaShi, frame type and circuit built-in 5 kinds.

The outer type is a small box, through serial communication, and the host connection mouth. The modem the greatest characteristic is very intuitive. The Modem communication and instructions have state indicator connection status.

Built-in general for desktops, is a insert CARDS. Built-in installed in case of expansion slot on the inside, saving the installation space and cable, also do not need additional power support. The connection is quite simple, the telephone Line joints of inserting the card “Line” in mouth, card another interface “please”, and telephone connected, at ordinary times unused device, the solution to a telephone with a little affected. Built-in shortcomings is need to be in on the project interrupt and COM port setting, installation more red tape.

PC KaShi, mainly used in notebook computers. Here the PC card is the abbreviation of mouth. Pick up PCMCIA PC KaShi Modem volume is small and exquisite, easy to carry, which is very suitable for travel.

Rack-mountable main used to provide the communication network access to company or a center machine room. A group of Modem is to focus on a box or covering, share a power, to provide users with Internet access.

Circuit built-in main notebook computer. Laptop computers in general have internal HP presario a900 battery adjustment of the circuit and modem I interface, the interface is RJ11 interface, also is the telephone interface.

In the foreseeable future, as the Internet broadband access and wireless access way, growing popularity of the modem will be eliminated.

(a local area network (LAN)

LAN is the most network application form, is also the subject of a Internet. A computer can construct LAN in just a few or hundreds of Taiwan between. In fact, thanks to the support network game domain has become the basic function of the computer operating system, so in a way, you can also put a computer as a local area network. The Internet is the set of countless LAN.

In a local area network, we are Shared between procedures, such as the document resources, and don’t have to passing back and forth disk, U plate and storage medium; But also through the network to enable computers sharing the same hardware, such as printer, modem, etc.; We can also with through Internet use computer to send and receive fax, convenient and quick and and the economy.

The characteristics of the local area HP CQ40 battery network

The distribution of local area network of small, less investment, simple configuration, it basically has the following features:

The transmission rate high: generally is 1-1000 Mbps, optical fiber high-speed network of up to 100 Mbps, 1000 Mbps;

Support the transmission medium variety;

Communication processing general by nic complete;

Transmission of good quality, low; ber

There are rules of topological structure.

The composition of the local area network:

LAN by server, users generally workstations, nic, transmission medium to four parts.

Server: running a network operating system, provide the hard disk,

File data and printer sharing and so on the service functions, is the core of the network control system. Common NOS mainly NetWare, Unix and Windows series 3 kinds.

NetWare: is the first real network operating system, its popular version has V3.12, V4.11, V5.0, demand for hardware, technology to improve, reliable low, a hold DuoZhong workstations and agreement, is suitable for the local area network operating system, as the document, print server service good performance. Novell NetWare is the product of the company, especially the development of the local area network to network made very great contribution, but not often unfortunately, the products and the company has been close to disappear, because they face opponent is Microsoft and Windows. Unix:-kind of typical multi-user NOS, mainly used in MSI Wind U100 battery super minicomputer, large machine. Support network file system service, provides the data applications, powerful, not easy control, command complex, from AT&T and introduced the remoted SCO.

Unix has DuoGe version and manufacturers, is also the most stable network operating system. But, early bad (known as professional > operation interface make it far from the big wide user groups.

Linux: a source close to the development and free Unix, the two big advantages decided their won’t be optional.

Windows series: a graphic application For distributed the integrity of the platform, the first of all network version comes from Windows3.1 version, is also the Windows For Workgroup later turned into Windows NT. It is easy to install and management, and the integration of a network management tools than India, wide wide prospect. This is at present the most popular system, although there are many shortcomings. The server is divided into a file server, to print the server, database server, in the Internet, and the Web, FTP, such as E-mail server. Network OS can support DuoZhong toward communication protocol, DuoZhong network adapter and workstations the direction of development.

The workstation: can have their own OS, independent work, through the operation work station network software, access Server sharing resources.

Network card: will the workstation type server even to the web, to realize the resource share and mutual communication, data transformation and electrical signals match.

Transmission medium: the common transmission medium have twisted pair, coaxial cable, optical fiber, etc.

Field work mode. Several kinds of nets

A dedicated server structure

Also known as “the workstation/file server” structure, with several microcomputer workstations and one or multiple file server through the communication lines connected workstation access server of files, sharing storage devices.

The file server natural by sharing the disk file for the main purpose. For the average for data transfer have been will be enough, but when database systems and other complex and be increased users with the use of the application system comes, service is already can’t take such tasks, because for the increase of the number of users, with the door for each service programs are increasing, every application is independent running large files, to the user feels very slow, resulting in a client 7 server mode.

Customer intends to server mode which one or several sets of large computer focus on a Shared database management and access, called the server, and other applications will handle work across the network computer, go up do other form of distributed processing system.

C/S model development mainly attributed to the database server. As the database of theory and technology in mature, a large number of data into the computer management. Rely on gradually with the network into technology and information system, form the professional Toshiba PA3450U-1BRS battery database server, the computer for data management way by the file management rise of database management mode.

The database, and file systems, focused on a different definition and access data backup and restore security, concurrent control and transaction management, implement such as choice retrieval and index sort and several library management function, it according to have enough power to do through its deal with the after that part of the customer need data and not the entire file through the network transmits to the client to reduce the transmission of the network, the load. C/S structure is database technology development and common application and bureau domain nets technology development of combining the results.

The network topology structure of equation in with special Server and C/S the same. In the equation, the network structure 1 without dedicated server, each workstation can up client effect might also be the server role.

With the computer processing power and speed to get substantially rise, a common PC has more than the original server processing power, enough to complete the server, so any affairs peer-to-peer network has become the mainstream of a local area network, especially in the daily do male environment.

As the main communication medium, and a lot of multimedia integration business network.

(two of the history of the Internet

In fact, the Internet is entirely based on network technology, is the development of network a necessary process. It is hard to put the Internet and the development of the network quite apart from history.

What is the Internet?

The Internet is an international collection of communication network, it combines modern communication technology and the modern computer technology in a body, the computer is between information exchange and international real now the resources sharing of good means. The Internet will all kinds of physical network to connect, make a whole, regardless of the similarities and differences of network type on the size of the geographical position and the difference, so accurate account of the Internet is: is a network of networks.

From the early APRAnet Internet web development, at the same time PA3382U-1BAS battery APRAnet up on packet switching technology and network interconnection technology research, and led to the emergence of the TCP/IP and development.

TCP/IP protocol is an important foundation of the Internet. Along with the rapid development of the Internet,

TCP/IP network technology in the influence of the field is more and more extensive, at present has become the DE facto standard.

TCP/IP application range is very wide, not only applicable to mainframes, also suitable for small machine and the PC and can be used not only to local area network, can also be used to the wan. In principle, any computer program as long as abide by the TCP/IP protocol, according to certain rules can access the Internet.

Is the so-called “the gander”, long-term since science and technology researchers sought to establish a unified network architecture, using an agreement to complete the task of communication system all eyes are standard TCP/IP based push forward, maybe 10 or 20 years later, will be implemented.

In the 1990 s, the computer technology, communication technology as well as based on the computer and network project based on the technology of computer network technology has developed rapidly. Especially, in 1993 the United States announced the establishment of national information infrastructure NII, many countries around the world have set their own NII and build, thus greatly promoted the development of the computer network technology, art computer network enters a new phase.

At present, the in the United States, for the core of high-speed computer network that the Internet has been formed, the Internet has become the most important by the human, the largest knowledge base. The U.S. government and respectively in 1996 and 1997 to investigate more rapid development of the Internet 2 (Internet2 reliable; and the Next Generation of the Internet (Next Generation Internet).

Can say, the network interconnection and high-speed computer network is becoming the latest generation of computer network the development direction of the network.

Here are the Internet can be roughly development process: and in 1983, TCP/IP become APRAnet standard communication protocol, on the sign

The real meaning of Internet appeared. And in 1984, the national science DV4 battery foundation began to infuse capital create NSFnet (national division

Learn fund nets, some of the major improvement for Internet provides funding. And in 1986, the U.S. national science foundation in the United States, with the support of the government, renting telecommunications companies communication lines has formed a new Ineternet backbone network, one country learn foundation network (NSFnet), was used to connect six super computer in the heart and the United States, colleges and institutes and academic institutions.

In 1989, at the same time, dissolved NCP is open to the public, so as to become

The most important communication for Internet backbone network. Throughout the 1980 s, | Internet sustainable development. Here’s worth remembering, the Internet is although had all the: many, but global nets fans (World Wide Web) did not appear, still can’t on the Internet freedom, can’t see picture, click on the download them and unless graphics program to open them. An important development has made, and people can search and retrieval information classification, the famous Archie method is “Gopher and Veronica), in January 1992, because of the number of users have written claw has increased dramatically, connected institutions of growing, the fields of application, gradually expand Internet association (ISOC) born child prodigies, it is a spontaneous users of the organization to make 10 remember printed a related standard must and the popularity of the Internet to promote goal; At the same time, the business community and communication industry beginning open Internet, pay attention to the commercialization of Internet growing calls. Or in 1992, when CERN (formerly of the European particle physics set laboratory) physicist Tim Berners Lee-invented the global network to help its physical XueYan investigate, big turn finally came. Tim Berners Lee was just for yourself-use and invented the nets, but soon it then began to spread like wildfire. More than 86? The use of a called the SGML markup language of composition, make web page formatting and contains hypertext links to become possible. No matter whether you know computer language, you can use Internet browser in the world roam. Click on information In 1993, Marc Andreesen and he in national supercomputing applications center

(NCSA) companions invented the first strong online browser, called Mosaic. Mosaic can view graphics, playing sounds, use Gopher, FTP, E-mail and news groups, this is to use the Internet all-in-one solution, with beautiful pictures. The rest of the things, it is indeed browser has evolved to history can handle audio and video and flow of all kinds of other modern function. This can make you feel about network in the 1980 s and 90 s, according to the development of Hobbes’ Internet Timeline, the Dell 9200 battery number of Internet host (especially the number > computer connected to the Internet from 1984 in 1000 to over 1992 in 1 million, and by 1997 the breakthrough 16 million.

The Internet in the last few years of the 20 th century with amazing pace, and development, with the modem speed increases, many Internet practical applications use with wide amount of larger with bandwidth (via the Internet and telephone line is the flow of information. A similar video and audio such application tied up a lot bandwidth). As soon as possible 1995, the national foundation announced and MCI cooperation construction plan of high speed data channels, providing 155 Mb/s high-speed backbone service (vBNS) to replace the existing NSFnet, each big communications company have also announced his Internet Internet plan. The age of the network that coming.

Assumption everyone passed the information on to his new understanding of all people, so, for in the end of the if everyone can know the news of our wine? If everyone to know each other words, so everyone know to get no label good wine to drink. But, even met a person greet every 10 minutes, see 99 guests also want to 16 hours, and party rarely continue & 1 long time. Therefore, you may feel the wine’s secrets to his friends of friends also just as well “to the end of the party, there must be left.

Paul ‘the proms and Alfred riley don’t agree with this view. The proms often quoted riley’s words, “mathematicians can drink coffee from a theorem to.” “Fruit, have so a cup of coffee, zhu hit by drink a often leads the theorem is with: if everyone know at least another guest, and soon everyone know to drink good wine. According to the proms and riley’s point of view, only half a small, can form the guests of the invisible covering all social network. That is to say, a guest in a few minutes earlier heard good wine business, to take will find that the bottle is empty.

Party guest problem is founded euler branch of mathematics ^ graph theory for a while with the part of the problem. Guests can be regarded as a point, and every met a man, set up the two men set up the social connection. Such a network, or as a graphic creation, points to be edge connection into a network. Computer use PA3399U-1BAS battery telephone line networking, in our body biological molecules through chemical reaction networks, the enterprise and the consumer through the trade union nets, neurons through the axon networking, networking, these islands through the bridge is network diagram example. No argument and edge is the nature of what, in the mathematician eyes, they are the same thing: network diagram or network.

Although the delicate, but will be simplified to network it network diagram is not simple. Clubs will, the Internet and cell or brain can use network diagram to each other, but said the difference between the different are high. It is hard to imagine, the human society and the existing between the cells have much in common. In the human society, we through the opportunity and the conscious decision with people; And in the cells, the control of the reaction between the molecules is relentless chemistry and physics law set. The nature of the link between the different network, its rules must be very different. On the surface, to find the system model describing all seems to be not to.

However, the ultimate goal of scientists, is to find the most simple is very complex phenomenon ? explanation. Therefore, the proms and riley put forward the delicate mathematical solutions, in a single structure description of complex network diagram. Different system following their completely different rules to build a network, the proms and riley it deliberately ignore them a different between the sex, obtained the nature can provide the most simple answer: random connected node. He concluded that create the most simple solution is network rolls the dice: choose two nodes, if thrust out 6, in between two add a link. If throws the other number, don’t connect the two nodes, but in another choose to open a beginning. Therefore, the proms and riley think network diagram and they represent the world from root the terms are random.

The proms like to say: “there is an old debate Li mathematics, whether it is human creation, or find out. In other words, is mathematics truth is inherently exist? Or the people want to out of?” For this problem, the proms a clear answer: mathematical justice and other absolute truth is the same, is already exists, what we do is to find them. Random graph looks delicate and simple, in his view is in eternity of justice. But now we know, random network of our universe organization for the role of extremely limited. Instead, the nature of several basic use double is, these we will in the following chapter was introduced. The proms founded the number of theoretical study justice, and graph theory, the development of random provides us with cheer on in the world of NC4400 battery new perspective. He himself to create the human brain and social nature of the secret and can not know, hence take bets on god like rolls the dice. His friends in Princeton, let the inauguration of Albert Einstein was tend to the opposite of the double point: “for the universe, god does not like dice.”

Now let us go back to the party and random graph theory to practice. Beginning, we have a big quantity node. And imitate the mode of random encounter between the guest, between the nodes with machine add a link. If only add a few, then can only make contact with some node to the. Continue to link down, inevitably will put some have matched quarter point and other nodes connected with DuoGe, form nodes with string. But when you add links enough to each node, to have an average of a link, can appear magical vision: a unique huge node string is produced. Also, says most of the node is governed by a single node string, and no matter from which node set out, can link node to the line by another node. It is to this time, your good wine to suffer, because such appeared giant node string, everyone can through own channel hear the gossip. Several experts will this phenomenon is called giant structure of the birth of the so-called giant structure contains all the node is part of the network. Physicists have described it as permeability (1100 , and will be strict previous state called phase change (blunt and read and Fang such as), this and water to icy moments of similar. Social scientists will say Dell 500M battery you object of study just group into a social group. Although different subjects in different terms expression, but the now like we all agree with the idea: when we randomly choose and will link up the network nodes, will cause the special situation happened in one network add a quantitative link, will produce sharp change. Previously, only exist some contain less make node of the isolated node string, each other mutual don’t know only in the group of the exchange within node. Later, appeared giant node string, almost everyone involved.

Mathematicians was born in Switzerland, euler his life in Berlin and the main time spent at st. Peter. He to mathematics, physics and engineering to every field of had a tremendous impact. He is great, not only lies in the importance of his discovery, no one can and, and its quality also is breathtaking. The works of euler part included in the “complete collection of euler (4)… Yang 0 ship, has now (4 compiled more than 73 volumes, the thickness of each volume is 600 pages. Life the last 17 years euler, that in 1766 he returned to fort to PA3587U-1BRS battery Peter to him at the age of 76, died at the age of, calm. Despite his personal life is full of tragedy, but his life works from this period. Half That includes a 775-page explore the moon operation of the papers, a quite an influential generation of math books, a three volumes this collection points. These # is and his weekly for st Petersburg scientific journals to write a mathematics paper writing out at the same time. The most exciting surprised the different is in that time, he basically don’t study, also don’t write. 1766 years back to st. Petersburg soon, euler lost sight of. In 1771 he made cataract surgery, but the operation failed, led to his completely blind. His thousands of pages of theory works is by memory of oral out.

30 years ago, when the euler eyesight is normal, he wrote a brief paper, discussion from elder brother in Johannesburg (you Mingcambio) an interesting question. Elder brother in Johannesburg euler in st. Petersburg home from far, is located within the territory of the Prussian an open city full of flowers. In the early eighteenth century, people also completely unexpected 1 city will be affected by the second world war ii the ravages of war. When one of the prints and this is located in the skin of river axel city thriving scene, river is full of goods, shore double fleet by local merchant family lived a rich in the rich life. And the healthy development of the financial strength to the city on the river, the city government uncommon built more than 7 bridge. Most of the bridge to endure Buddha “Yi) at Cardiff this beautiful ? island. The island is skin geer river two branches of caught in the middle of sand bars, a city located in the island. In addition to the two bridge will be skin geer river two branches of even

Figure 2.1 at the bridge in Johannesburg. 1875 years ago in Johannesburg in the layout of the elder brother, of which the nanotubes is Buddha said Cardiff 0 is the land, the island, skin geer two branches of the river they caught in the middle. Elder brother in Johannesburg problem requires people to find through the city seven bridge and each bridge only go again path. In 1736, mino raiola Hal DE euler discusses the problem invented the graph theory. He will be four land areas as “dot” (eight to!) ), each bridge as a side 4 to 8 >, this got includes four points, seven side of the chart. Then he proved the elder brother in Johannesburg figure, it does not exist when bridge once walked only through the city and the route. Together (figure 2.1 . Living in Johannesburg elder brother who once living comfortably rich, especially like to play intelligence game, one of the “seven bridge problem” is like this: “the people could not repeat through seven bridge?” at that time who also have no way to do this. Then, in 1875, built HP dv2000 battery a new Bridges, people found that can ask according to the will go through.

Xinqiao construction in the 150 years ago, which was in 1736, euler put forward a powerful mathematical reasoning, in accordance with specified at 7 bridge layout, doesn’t exist puzzle required in the path. He that article brief paper not only solve the elder brother nice? Problems, but also in accidentally opened a new math: graph theory. Double township, graph theory has become the foundation of network problems thinking. After the death of the euler several will, graph theory has gradually mature, most development during this mathematicians have made a contribution. In order to open the gate, we network field first come to review prompted euler thinking first graph theory thinking of the process.

The simple and exquisite euler proof, even without learn training, also very easy to understand. But, to write the history of this question is not his proof of fruit, but he and solve problems among the process. The most amazing to party euler, to get the elder brother in Johannesburg bridge issue is seen as a starting point by point and links the edge of a graph of. For this problem, he points to represent each separated by rivers land areas respectively, employing, 8,and he said. The next 0 will pick up the bridge as the land even edge. So he would get from point and edge of graphics.

Euler through a simple found proof that the elder brother in Johannesburg does not exist through each bridge a route through the city. The discovery is: figure with the edge of the has an odd number of points, not the starting point of the trip, what, is the destination. And through all the continuous route bridge can have a starting point 0 and a destination. That way, if a figure with two of the edge of the has an odd number of points, not that there exists a route. In the elder brother in Johannesburg figure this point has four, so can’t find the necessary route. And the purpose of the euler mentioned in argument, it is to show whether there are not take & route in our argument is clever, but in the method of attributes. Figure itself The bridge with elder brother, for example, no matter how Dell Inspiron 1100 battery much we clever, and also cannot find the necessary road stomach in Johannesburg city finally believed the euler argument, not in vain to search for the most convenient route. In 1875, they in 8 and (: built a new bridge between the two points, the edge between increased to 4. This will only have two belt has an odd number of edge points (and 0 >. This way, looking for the most simple route is very straight to pick up the search for this line. Maybe the secret, it is also the basic principle of building a bridge?

Broken the world wide web We thought, the XIX: research report published, each big search engine will add great strength, improve its coverage. The results are not. After a year, in February 1999, Lawrence and giles to calculate the scale of the world wide web, found that more than doubled, document the total to 800 million. However the search engine but didn’t keep up with this? Add long pace. In fact, their coverage be worse. This time, ranked first is oil, covering the 160/0 of the world wide web. 901801 and 1813 people in 11 “is now: their coverage rates were back at 11 less. And less. When 000 15. 16 coverage rate is 1. 8 . All these search engines can add up to cover only the network 40 less.. This means that the any search engine will ignore 6/10 and your Chad inquiry concerning results. In fact they haven’t seen these web pages.

But in the end the XIX: report or triggered the fierce competition in the search engine. The scale of the search engine finally become important factors. The new search engines? address is eight lamp to meet the continent vomit (3), a look at ‘claws that the company’s objective and eight force broke out between Fletcher in the struggle for Lenovo L410 battery control of the. In January 2000, the state will (3) claw index number hit the 30 million mark. Six “up soon. In June 2000, search engine nova only, when the tuen become important competitors, the sudden broke 20 50 million mark. soon reached the Numbers, another new search engine double will knock. 0001 also Fielding to follow. In June 2001, 000 of the new record, the first breakthrough 1 billion documents mark.

Until now, 0008, has been far ahead. Trying to cover the whole of the Internet with oil out. 00111 second, an index of 60 million document, there are 55 million copies. Search engine performance becomes more and more good, this is positive news. No, there is also the problems: the world wide web growth also more and more quickly.

Most search engines that there was no attempt to index the entire network. @ simple reason: with most of the search engine index document, not necessarily the best. Shaw, but if you’re looking for information very partial, then the engine of the high rate of effect will be good cheer. But, if the search is a common topic, more index does not necessarily bring better results. @ Most of us, see the search engine to return to thousands of thousands of search results, I have lost. We don’t want to see more in yue a search will bring millions of result. Therefore, after more than a certain point, change into the algorithm from the search engines database to select the best pages, than mere search results more beneficial to the increase.

Involve the world wide web browsing, whether artificial browse or network robot browsing, economic incentives (or lack of such incentive are no longer is the only limiting factor. The world wide web of topological structure limits we couldn’t see the whole network of the world wide web is a scale-free network, and the center of the 10000-by node, node and links to form. But, next we will note that this a large scale, and construct topology and countless small scale structure, they are serious impact on the us through the click can find the link. ability

Although the world wide web has 1 billion more documents, but the 19 degrees to the world wide web space, easy to browse. It is very great, also is very small. But the world wide web back after the small world but some misled effect. If there is a connection between two documents road, this path should normally be diameter is short. But in fact, not all pages can mutual links. Any a page from the start, we can only links to jump to 24. 4 other document. The rest of the document to us is not visible, can’t clear at to.

The results of generation, is due to technical reasons, the world wide web PA3285U-2BRS battery links in the direction of stomach stomach. In other words, along a particular 11 address, we only only

To travel. In a network, if the two nodes between no link, you

Through the other nodes will they even up: for example, if want from six to you can start from node to node, people begin to 8, and the 8 and node connected, and point to the link But fell back nodes cannot. In the network, you have to just can go, also can pour to go, six-if it is the, the yao in turn. being ok. However, in the network, but we can’t guarantee reverse path must exist. Most likely, you want to come back, they had to go in the path of the different: starting from 0, you may need to visit a lot of people to return to between nodes. The world wide web is full of the path to. This essentially decides the world wide webseaworthiness, or call can browse the sex.

These robot design, is the intent of the high speed and high efficient a they are on the world wide web one fast after a sports car they link, sniffer along the road. And these machine device, ZhengHaoXiong design than that used to draw a map of the world wide web robot is like an ordinary little beetle, but I still like it very much. It’s like a personal life buy the first car, will be affected by the favour of special master. Although this web robot almost every other day will crash, but also often inadvertently put refused to network access web robot take home.

We soon found the little engine design with we draw the world wide web map is an Lenovo L510 battery impossible dream. Although it is often wrong, often strike, but eventually display to 300000 pages, with it’s enough to make we found the world wide web is a scale-free network. In this stage, we had closed its maybe a little early a. If we allow it to collect more the world wide web, might be the sample found the complex network of some other characteristics. For the world wide web, search engine view more than we found that the scope of the. Study of these huge sample study I have made a some exciting discovery. They found that the world wide web has cracked into different mainland and community, this limited us in the network world behavior. But they again from phase spear said the world wide web and many shield were found in the area, was never any visitor and network robot visited that land. The most important is, we know, ten thousand d nets structure from the net surfing to seven for democratic system, such as in effect.

Only a few years ago, we think we have to understand all of the world wide web. When there are some very popular way, such as “if use six Fletcher search words, may not online doesn’t exist this information”; Or “901801 is the first to to the whole network? Indexing network robots”. We were so trust search engine, think that they can tell us everything of the world wide web. But # 1998 to April, all this suddenly changed. When a major search engines spokesman said: “we pay more attention to the quality of the index, not quantity.” Another? Some web sites, said: “there are some further page is just not worth the index”. Exactly what the problem is? This kind of attitude u-turn, is born on 3 April 1998 science magazine published a research paper. The three pages of paper, the change of the Fletcher we stored in on the world wide web information ability shaw confidence.

The author Steve “Lawrence false blinked and lee (false) giles write this essay also is not to doubt the credibility of the search engine. They post in Japan electrical company based in Princeton, New Jersey, both the institute of machine learning ability, this is interested in computer science FangXing–not a new topic. They designed a yuan search engine, also is a network called “I call the robot, 11 ^”, the robot can 13 according to a search query each major search engines conditions website. Work done half later, they realized that the robot can still finish design not think of work: help them an estimated ten thousand d nets of scale.

I call for several search engines contains a particular enumerate the words which have the documents, such as 0, assist (crystal, if each search engine in the network can access all the documents and index, then they return is inevitably the same document list. And in fact, different search engines to return to list but few have the same. However, the total have overlap between list. For example, in eight find the word contains 1000 documents, 343 also observed in 901801 to return to search list. With overlapping document obtained by PA3285U-1BRS battery dividing the number of people return back to the total number of document, it has received 901801 contains the ratio of the document. According to report way, in December of 1997index number of documents for 1. 100 million, the Japanese electrical male department (the team estimated at that time) of the world wide web page number is always 1 million 110/0.343, or 320 million documents. Now the number is not very big. But in 1997, the plan Bi than the most accurate estimation results also big 1 times.

1998 years ago, about the size of the world wide web, we believe that the search engine tell us everything. They are, after all, should know about these. Lawrence and giles do similar research shows that need milestone on the world wide web for scientific research in a world wide web that can and should be through the system, can reproduce the way of the inquiry. However they on search engine in the draw maps of the world wide web ability, but let us send now cover and not get up.