计算机网络英文文献
计算机网络英文资料
NetworkThe Internet is a worldwide, publicly accessible series of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP). It is a "network of networks" that consists of millions of smaller domestic, academic, business, and government networks, which together carry various information and services, such as electronic mail, online chat, file transfer, and the interlinked web pages a nd other resources of the World Wide Web (WWW).The Internet and the World Wide Web are not one and the same. The Internet is a collection of interconnected computer networks, linked by copper wires, fiber-optic cables, wireless connections, etc. In contrast, the Web is a collection of interconnected documents and other resources, linked by hyperlinks and URLs. The World Wide Web is one of the services accessible via the Internet, along with various others including e-mail, file sharing, online gaming and others described below. However, "the Internet" and "the Web" are commonly used interchangeably in non-technical settings.Computer NetworkA computer network is an interconnected group of computers. Networks may be classified by the network layer at which they operate according to basic reference models considered as standards in the industry, such as the five-layer Internet Protocol Suite model. While the seven-layer Open Systems Interconnection (OSI) reference model is better known in academia, the majority of networks use the Internet Protocol Suite (IP).In computer science, a data structure is a way of storing data in a computer so that it can be used efficiently. Often a carefully chosen data structure will allow the most efficient algorithm to be used. The choice of the data structure often begins from the choice of an abstract data type. A well-designed data structure allows a variety of critical operations to be performed, using as few resources, both execution time and memory space, as possible. Data structures are implemented by a programming language as data types and the references and operations they provide.Different kinds of data structures are suited to different kinds of applications, and some are highly specialized to certain tasks. For example, B-trees are particularly well-suited for implementation of databases, while networks of machines rely on routing tables to function.In the design of many types of programs, the choice of data structuresis a primary design consideration, as experience in building large systems has shown that the difficulty of implementation and the quality and performance of the final result depends heavily on choosing the best data structure. After the data structures are chosen, the algorithms to be used often become relatively obvious. Sometimes things work in the opposite direction - data structures are chosen because certain key tasks have algorithms that work best with particular data structures. In either case, the choice of appropriate data structures is crucial.This insight has given rise to many formalised design methods and programming languages in which data structures, rather than algorithms, are the key organising factor. Most languages feature some sort of module system, allowing data structures to be safely reused in different applications by hiding their verified implementation details behind controlled interfaces. Object-oriented programming languages such as C++ and Java in particular use classes for this purpose.Since data structures are so crucial, many of them are included in standard libraries of modern programming languages and environments, such as C++'s Standard T emplate Library containers, the Java Collections Framework, and the Microsoft .NET Framework.The fundamental building blocks of most data structures are arrays, records, discriminated unions, and references. For example, the nullable reference, a reference which can be null, is a combination of references and discriminated unions, and the simplest linked data structure, the linked list, is built from records and nullable references.Data structures represent implementations or interfaces: A data structure can be viewed as an interface between two functions or as an implementation of methods to access storage that is organized according to the associated data type.Binary treeIP stack connectionsUDP encapsulation。
计算机网络英语作文
计算机网络英语作文Title: The Importance of Computer Networks in Today's World。
In today's interconnected world, computer networks play a crucial role in facilitating communication, sharing resources, and enabling collaboration on a global scale. From personal communication to large-scale businesses and government operations, computer networks have become an integral part of our daily lives. In this essay, we will delve into the significance of computer networks and explore how they have revolutionized various aspects of our society.First and foremost, computer networks have transformed the way we communicate. Through the internet, individuals can connect with each other regardless of geographical barriers. Email, instant messaging, social media platforms, and video conferencing tools have become indispensable means of communication in both personal and professionalsettings. This seamless exchange of information has greatly enhanced productivity and efficiency in various sectors.Moreover, computer networks facilitate the sharing and dissemination of information on a massive scale. Online platforms enable users to access vast repositories of knowledge, ranging from educational resources to entertainment content. The proliferation of online libraries, digital archives, and streaming services has democratized access to information, empowering individuals to learn and grow irrespective of their location or socioeconomic status.Furthermore, computer networks have revolutionized the way businesses operate. Through e-commerce platforms, companies can reach a global audience and conduct transactions seamlessly. Supply chain management systems rely on computer networks to coordinate the flow of goods and services efficiently. Moreover, cloud computing services offer businesses scalable and cost-effective solutions for storage, data processing, and software deployment. These technological advancements have not onlyimproved operational efficiency but also fostered innovation and entrepreneurship.In addition to enhancing communication and collaboration, computer networks play a crucial role in ensuring the security and integrity of data. With the proliferation of cyber threats, securing network infrastructure and safeguarding sensitive information have become paramount concerns for organizations and individuals alike. Encryption technologies, firewalls, and intrusion detection systems help mitigate risks and protect against unauthorized access and malicious activities. Moreover, ongoing research and development efforts are focused on enhancing cybersecurity measures to address emerging threats and vulnerabilities.Furthermore, computer networks have transformed the way we access and consume entertainment and media content. Streaming services, online gaming platforms, and social media networks have become ubiquitous forms of entertainment, offering users a diverse array of content at their fingertips. The advent of high-speed internetconnectivity has enabled seamless multimedia streaming, immersive gaming experiences, and real-time interaction with content creators and fellow users.Additionally, computer networks have revolutionized the field of healthcare by enabling telemedicine and remote patient monitoring. Patients can consult healthcare professionals, access medical records, and receive diagnoses and treatment recommendations remotely, eliminating the need for physical visits to healthcare facilities. This not only improves access to healthcare services, particularly in underserved areas, but also enhances patient convenience and reduces healthcare costs.In conclusion, computer networks have transformed the way we communicate, collaborate, conduct business, and access information and entertainment. From personal interactions to global transactions, computer networks have become the backbone of our interconnected world. However, it is essential to recognize the importance of ensuring the security and integrity of these networks to mitigate risks and safeguard against cyber threats. As technologycontinues to evolve, computer networks will undoubtedly play an even more significant role in shaping the future of our society.。
计算机网络安全论文参考文献
计算机网络安全论文参考文献以下是一篇关于计算机网络安全的论文参考文献：[1] Stallings, W. (2013). Network security essentials: Applications and standards (Vol. 1). Pearson.这本书探讨了计算机网络安全的基本概念、原理和技术。
它提供了对各种网络安全协议、算法和策略的详细介绍，以及实际应用和标准的示例。
[2] Kurose, J. F., & Ross, K. W. (2010). Computer networking: a top-down approach. Pearson Education.这本书是计算机网络的经典教材，它详细介绍了计算机网络体系结构和协议的工作原理。
它还包括网络安全的基本原理和技术，如加密、身份验证和访问控制。
[3] Anderson, R. (2008). Security engineering: a guide to building dependable distributed systems. John Wiley & Sons.这本书通过分析实际系统的安全问题和解决方案，提供了构建安全分布式系统的指南。
它涵盖了许多关键安全概念和技术，如访问控制、防火墙、入侵检测和身份管理。
[4] Pfleeger, C. P., & Pfleeger, S. L. (2007). Security in computing. Prentice Hall.该书介绍了计算机安全的基本概念、原理和技术，如密码学、访问控制、网络安全和软件安全。
它还提供了关于安全策略和风险管理的实际指南。
[5] Schneier, B. (2015). Applied cryptography: protocols,algorithms, and source code in C. John Wiley & Sons.这本书是密码学的经典教材，它详细介绍了密码学的基本概念、原理和算法。
外文文献—计算机网络
英文原文：Computer networkA computer network, often simply referred to as a network, is a collection of computers and devices interconnected by communications channels that facilitate communications among users and allows users to share resources. Networks may be classified according to a wide variety of characteristics. A computer network allows sharing of resources and information among interconnected devices.History ：Early networks of communicating computers included the military radar system Semi-Automatic Ground Environment (SAGE) and its relative the commercial airline reservation system Semi-Automatic Business Research Environment (SABRE),started in the late 1950s.[1][2]When Russia launched His SPUTNIK Satellite in Space In 1957.The American Started Agency Names ADV ANCE RESEARCH PROJECT AGENCY (ARPA) & launched THis 1st Satellite Within 18 Month After Establishment.Then Sharing Of TheInformation InAnother Computer They Use ARPANET.And This All Responsibility On America's Dr.LIED LIEDER.Then in 1969,ARPANET Comes in INDIA And INDIAN Switched This Name To NETWORK. In the 1960s, the Advanced Research Projects Agency (ARPA) started funding the design of the Advanced Research Projects Agency Network (ARPANET) for the United States Department of Defense. Development of the network began in 1969, based on designs developed during the1960s.[3] The ARPANET evolved into the modern Internet.Purpose ：Computer networks can be used for a variety of purposes: Facilitating communications. Using a network, people can communicate efficiently and easily via email, instant messaging, chat rooms, telephone, video telephone calls, and video conferencing.Sharing hardware.：In a networked environment, each computer on a network may access and use hardware resources on the network, such as printing a document on a shared network printer.Sharing files, data, and information. In a network environment, authorized user may access data and information stored on other computers on the network. The capability of providing access to data and information on shared storage devices is an important feature of many networks.Sharing software.：Users connected to a network may run application programs on remote computers.information preservationSecurityNetwork classification The following list presents categories used for classifying networks.Connection method ：Computer networks can be classified according to thehardware and software technology that is used to interconnect the individual devices in the network, such as optical fiber, Ethernet, wireless LAN, HomePNA, power line communication or G.hn.Ethernet as it is defined by IEEE 802 utilizes various standards and mediums that enable communication between devices. Frequently deployed devices include hubs, switches, bridges, or routers. Wireless LAN technology is designed to connect devices without wiring. These devices use radio waves or infrared signals as a transmission medium. ITU-T G.hn technology uses existing home wiring (coaxial cable, phone lines and power lines) to create a high-speed (up to 1 Gigabit/s) local area network.Wired technologies ：Twisted pair wire is the most widely used medium for telecommunication.Twisted-pair cabling consist of copper wires that are twisted into pairs. Ordinary telephone wires consist of two insulated copper wires twisted into pairs. Computer networking cabling consist of 4 pairs of copper cabling that can be utilized for both voice and data transmission. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. The transmission speed ranges from 2 million bits per second to 100 million bits per second. Twisted pair cabling comes in two forms which are Unshielded Twisted Pair (UTP) and Shielded twisted-pair (STP) which are rated in categories which are manufactured in different increments for various scenarios.Coaxial cable is widely used for cable television systems, office buildings, and other work-sites for local area networks. The cables consist of copper or aluminum wire wrapped with insulating layer typically of a flexible material with a high dielectric constant, all of which are surrounded by a conductive layer. The layers of insulation help minimize interference and distortion. Transmissionspeed range from 200 million to more than 500 million bits per second.Optical fiber cable consists of one or more filaments of glass fiber wrapped in protective layers. It transmits light which can travel over extended distances.Fiber-optic cables are not affected by electromagnetic radiation. Transmission speedmay reach trillions of bits per second. The transmission speed of fiber optics is hundreds of times faster than for coaxial cables and thousands of times faster than atwisted-pair wire.[citation needed]Wireless technologies ：Terrestrial microwave – Terrestrial microwaves use Earth-based transmitter and receiver. The equipment looks similar to satellite dishes. Terrestrial microwaves use low-gigahertz range, which limits all communications to line-of-sight. Path between relay stations spaced approx, 30 miles apart. Microwave antennas are usually placed on top of buildings, towers, hills, and mountain peaks.Communications satellites –The satellites use microwave radio as their telecommunications medium which are not deflected by the Earth's atmosphere. The satellites are stationed in space, typically 22,000 miles (for geosynchronous satellites) above the equator. These Earth-orbiting systems are capable of receiving and relayingvoice, data, and TV signals.Cellular and PCS systems – Use several radio communications technologies. The systems are divided to different geographic areas. Each area has a low-power transmitter or radio relay antenna device to relay calls from one area to the next area.Wireless LANs –Wireless local area network use a high-frequency radio technology similar to digital cellular and a low-frequency radio technology. Wireless LANs use spread spectrum technology to enable communication between multiple devices in a limited area. An example of open-standards wireless radio-wave technology is IEEE.Infrared communication , which can transmit signals between devices within small distances not more than 10 meters peer to peer or ( face to face ) without any body in the line of transmitting.Scale：Networks are often classified as local area network (LAN), wide area network (WAN), metropolitan area network (MAN), personal area network (PAN), virtual private network (VPN), campus area network (CAN), storage area network (SAN), and others, depending on their scale, scope and purpose, e.g., controller area network (CAN) usage, trust level, and access right often differ between these types of networks. LANs tend to be designed for internal use by an organization's internal systems and employees in individual physical locations, such as a building, while WANs may connect physically separate parts of an organization and may include connections to third parties.Functional relationship (network architecture) ：Computer networks may be classified according to the functional relationships which exist amongthe elements of the network,e.g., active networking, client–server, Wireless ad hoc network andpeer-to-peer (workgroup) architecture.Network topology ：Main article: Network topology Computer networks may be classified according to the network topology upon which the network is based, such as bus network, star network, ring network, mesh network.Network topology is the coordination by which devices in the network are arranged in their logical relations to one another, independent of physical arrangement. Even if networked computers are physically placed in a linear arrangement and are connected to a hub, the network has a star topology, rather than a bus topology. In this regard the visual and operational characteristics of a network are distinct. Networks may be classified based on the method of data used to convey the data, these include digital and analog networks.Types of networks based on physical scopeCommon types of computer networks may be identified by their scale.Local area network：A local area network (LAN) is a network that connects computers and devices in a limited geographical area such as home, school, computer laboratory, office building, or closely positioned group of buildings. Each computer or device on the network is a node. Current wired LANs are most likely to be based on Ethernettechnology, although new standards like ITU-T G.hn also provide a way to create a wired LAN using existing home wires (coaxial cables, phone lines and power lines).[4]Typical library network, in a branching tree topology and controlled access to resources All interconnected devices must understand the network layer (layer 3), because they are handling multiple subnets (the different colors). Those inside the library, which have only 10/100 Mbit/s Ethernet connections to the user device and a Gigabit Ethernet connection to the central router, could be called "layer 3 switches" because they only have Ethernet interfaces and must understand IP. It would be more correct to call them access routers, where the router at the top is a distribution router thatconnects to the Internet and academic networks' customer access routers.The defining characteristics of LANs, in contrast to WANs (Wide Area Networks), include their higher data transfer rates, smaller geographic range, and no need for leased telecommunication lines. Current Ethernet or other IEEE 802.3 LAN technologies operate at speeds up to 10 Gbit/s. This is the data transfer rate. IEEE has projects investigating the standardization of 40 and 100 Gbit/s.[5]Personal area network :A personal area network (PAN) is a computer network used for communication among computer and different information technological devices close to one person. Some examples of devices that are used in a PAN are personal computers, printers, fax machines, telephones, PDAs, scanners, and even video game consoles. A PAN may include wired and wireless devices. The reach of a PAN typically extends to 10 meters.[6] A wired PAN is usually constructed with USB and Firewire connections while technologies such as Bluetooth and infrared communication typically form a wireless PAN.Home area network :A home area network (HAN) is a residential LAN which is used for communication between digital devices typically deployed in the home, usually a small number of personal computers and accessories, such as printers and mobile computing devices. An important function is the sharing of Internet access, often a broadband service through a CATV or Digital Subscriber Line (DSL) provider. It can also be referred to as an office area network (OAN).Wide area network :A wide area network (WAN) is a computer network that covers a large geographic area such as a city, country, or spans even intercontinental distances, using a communications channel that combines many types of media such as telephone lines, cables, and air waves. A WAN often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer.Campus network :A campus network is a computer network made up of an interconnection of local area networks (LAN's) within a limited geographical area. The networkingequipments (switches, routers) and transmission media (optical fiber, copper plant, Cat5 cabling are almost entirely owned (by the campus tenant / owner: an enterprise, university, government etc.).In the case of a university campus-based campus network, the network is likely to link a variety of campus buildings including; academic departments, the university library and student residence halls.Metropolitan area network:A Metropolitan area network is a large computer network that usually spans a city or alarge campus. Sample EPN made of Frame relay WAN connections and dialup remote access.Enterprise private network :An enterprise private network is a network build by an enterprise to interconnect various company sites, e.g., production sites, head offices, remote offices, shops, in order to share computer resources.Virtual private network :A virtual private network (VPN) is a computer network in which some of the links between nodes are carried by open connections or virtual circuits in some larger network (e.g., the Internet) instead of by physical wires. The data link layer protocols of the virtual network are said to be tunneled through thelarger network when this is the case. One common application is secure communications through the public Internet, but a VPN need not have explicit security features, such as authentication or content encryption. VPNs, for example, can be used to separate the traffic of different user communities over an underlying network with strong security features.VPN may have best-effort performance, or may have a defined service level agreement (SLA) between the VPN customer and the VPN service provider. Generally, a VPN has a topology more complex than point-to-point.Internetwork :An internetwork is the connection of two or more private computer networks via a common routing technology (OSI Layer 3) using routers. The Internet is an aggregation of many internetworks, hence its name was shortened to Internet.Backbone network :A Backbone network (BBN) A backbone network or network backbone is part of a computer network infrastructure that interconnects various pieces of network, providing a path for the exchange of information between different LANs or subnetworks.[1][2] A backbone can tie together diverse networks in the same building, in different buildings in a campus environment, or over wide areas. Normally, the backbone's capacity is greater than the networks connected to it.A large corporation that has many locations may have a backbone network that ties all of the locations together, for example, if a server cluster needs to be accessed by different departments of a company that are located at different geographical locations.The pieces of the network connections (for example: ethernet, wireless) that bring these departments together is often mentioned as network backbone. Networkcongestion is often taken into consideration while designing backbones. Backbone networks should not be confused with the Internet backbone.Global area network:A global area network (GAN) is a network used for supporting mobile communications across an arbitrary number of wireless LANs, satellite coverage areas, etc. The key challenge in mobile communications is handing off the user communications from one local coverage area to the next. In IEEE Project 802, this involves a succession of terrestrial wireless LANs.[7]Internet :The Internet is a global system of interconnected governmental, academic, corporate, public, and private computer networks. It is based on the networking technologies of the Internet Protocol Suite. It is the successor of the Advanced Research ProjectsAgency Network (ARPANET) developed by DARPA of the United States Department of Defense. The Internet is also the communications backbone underlying the World Wide Web (WWW).Intranets and extranets :Intranets and extranets are parts or extensions of a computer network, usually a local area network. An intranet is a set of networks, using the Internet Protocol and IP-based tools such as web browsers and file transfer applications, that is under the control of a single administrative entity. That administrative entity closes the intranet to all but specific, authorized users. Most commonly, an intranet is the internal network of an organization. A large intranet will typically have at least one web server to provide users with organizational information.An extranet is a network that is limited in scope to a single organization or entity and also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities—a company's customers may be given access to some part of its intranet—while at the same time the customers may not be considered trusted from a security standpoint. Technically, an extranet may also be categorized as a CAN, MAN, WAN, or other type of network, although an extranet cannot consist of a single LAN; it must have at least one connection with an external network.Overlay network:An overlay network is a virtual computer network that is built on top of another network. Nodes in the overlay are connected by virtual or logical links, each of which corresponds to a path, perhaps through many physical links, in the underlying network.中文译文：计算机网络计算机网络，通常简单的被称作是一种网络，是一家集电脑和设备为一体的沟通渠道，便于用户之间的沟通交流和资源共享。
计算机网络(第四版)英文原版1.9 Summary
A factor in the delay of a store-and-forward packet-switching system is how long it takes to store and forward a packet through a switch. If switching time is 10 μsec, is this likely to be a major factor in the response of a client-server system where the client is in New York and the server is in California? Assume the propagation speed in copper and fiber to be 2/3 the speed of light in vacuum.
Well-known networks include the Internet, ATM networks, Ethernet, and the IEEE 802.11 wireless LAN. The Internet evolved from the ARPANET, to which other networks were added to form an internetwork. The present Internet is actually a collection of many thousands of networks, rather than a single network. What characterizes it is the use of the TCP/IP protocol stack throughout. ATM is widely used inside the telephone system for long-haul data traffic. Ethernet is the most popular LAN and is present in most large companies and universities. Finally, wireless LANs at surprisingly high speeds (up to 54 Mbps) are beginning to be widely deployed.
有关计算机网络的英文作文
有关计算机网络的英文作文Computer Networks: The Foundation of Modern Communication.In the digital landscape of the 21st century, computer networks have become an indispensable part of our lives. They connect countless devices, facilitating seamless communication, data sharing, and access to a vast array of information and resources. Understanding the fundamentals of computer networks is crucial for navigating this interconnected world.Definition and Components.A computer network is a collection of interconnected computers that can communicate with each other and share resources. These networks can vary in size, from small home networks connecting a few devices to massive global networks connecting millions of computers.Essential components of a computer network include:Network Interface Card (NIC): A device in each computer that enables it to connect to the network.Transmission Medium: The physical infrastructure, such as cables, wires, or wireless signals, that transmits data between devices.Network Protocols: Rules that govern data transmission, ensuring compatibility and communication among devices.Network Operating System (NOS): Software that manages the network's resources and ensures its smooth operation.Types of Computer Networks.Numerous types of computer networks exist, eachtailored to specific purposes:Local Area Networks (LANs): Connect devices within a limited geographic area, such as a building or campus.Wide Area Networks (WANs): Connect devices over a broader geographic area, such as between cities or countries.Metropolitan Area Networks (MANs): Connect devices within a metropolitan area, typically spanning a city or region.Global Area Networks (GANs): Connect devices worldwide, providing global connectivity.Wireless Networks: Connect devices without the use of physical cables, often using radio frequencies or Wi-Fi.Network Topologies.The arrangement of devices within a network is known as its topology. Common topologies include:Bus: A single communication channel that all devices connect to.Ring: A circular structure where each device connects to two others.Star: A central hub connects to all devices.Mesh: A redundant structure where each device connects to multiple others.Network Protocols.Protocols are essential for ensuring communication and interoperability among devices on a network. Some key protocols include:Transmission Control Protocol (TCP): A reliable protocol for transmitting data across the Internet.Internet Protocol (IP): The addressing scheme for devices on the Internet.Hypertext Transfer Protocol (HTTP): The protocol usedfor web browsing.File Transfer Protocol (FTP): The protocol for file transfer between computers.Domain Name System (DNS): The service that translates domain names into IP addresses.Network Security.Protecting computer networks from unauthorized access, threats, and vulnerabilities is paramount. Network security measures include:Firewalls: Software or hardware that monitors and controls network traffic.Intrusion Detection Systems (IDSs): Devices that detect and report suspicious network activity.Virtual Private Networks (VPNs): Secure connections that allow remote users to access private networks.Encryption: Converting data into a secure format to prevent unauthorized access.Applications and Benefits of Computer Networks.Computer networks have revolutionized communication and data sharing:Access to Information: Networks provide access to a vast repository of information and resources on the Internet.Communication: Networks facilitate real-time communication through email, instant messaging, and video conferencing.Collaboration: Networks enable collaboration between remote teams and individuals through shared documents, video meetings, and project management tools.Entertainment: Networks provide access to onlinegaming, streaming services, and social media platforms.E-Commerce: Networks enable online shopping and banking, expanding business opportunities and consumer choices.Conclusion.Computer networks are the backbone of modern communication and information exchange. They have transformed the way we live, work, and interact with each other. Understanding the fundamentals of computer networks is essential for navigating the digital landscape and leveraging its immense benefits. As technology continues to evolve, networks will play an increasingly crucial role in shaping our connected world.。
计算机网络 外文文献 外文翻译 英文文献 新技术的计算机网络
文献来源：/Freepaper/Jisuanji/wangluo/200810/28156.html一、原文New technique of the computer networkAbstractThe 21 century is an ages of the information economy, being the computer network technique of representative techniques this ages, will be at very fast speed develop soon in continuously creatively, and will go deep into the people's work, life and study. Therefore, control this technique and then seem to be more to deliver the importance. Now I mainly introduce the new technique of a few networks in actuality live of application.keywordsInternet Digital Certificates Digital Wallets Grid Storage1. ForewordInternet turns 36, still a work in progressThirty-six years after computer scientists at UCLA linked two bulky computers using a 15-foot gray cable, testing a new way for exchanging data over networks, what would ultimately become the Internet remains a work in progress.University researchers are experimenting with ways to increase its capacity and speed. Programmers are trying to imbue Web pages with intelligence. And work is underway to re-engineer the network to reduce Spam (junk mail) and security troubles.All the while threats loom: Critics warn that commercial, legal and political pressures could hinder the types of innovations that made the Internet what it is today.Stephen Crocker and Vinton Cerf were among the graduate students who joined UCLA professor Len Klein rock in an engineering lab on Sept. 2, 1969, as bits of meaningless test data flowed silently between the two computers. By January, three other "nodes" joined the fledgling network.Then came e-mail a few years later, a core communications protocol called TCP/IP in the late 70s, the domain name system in the 80s and the World Wide Web - now thesecond most popular application behind e-mail - in 1990. The Internet expanded beyond its initial military and educational domain into businesses and homes around the world.Today, Crocker continues work on the Internet, designing better tools for collaboration. And as security chairman for the Internet's key oversight body, he is trying to defend the core addressing system from outside threats.He acknowledges the Internet he helped build is far from finished, and changes are in store to meet growing demands for multimedia. Network providers now make only "best efforts" at delivering data packets, and Crocker said better guarantees are needed to prevent the skips and stutters now common with video.Cerf, now at MCI Inc., said he wished he could have designed the Internet with security built-in. Microsoft Corp.Yahoo Inc. and America Online Inc., among others, are currently trying to retrofit the network so e-mail senders can be authenticated - a way to cut down on junk messages sent using spoofed addresses.Many features being developed today wouldn't have been possible at birth given the slower computing speeds and narrower Internet pipes, or bandwidth, Cerf said.2.Digital CertificatesDigital certificates are data files used to establish the identity of people and electronic assets on the Internet. They allow for secure, encrypted online communication and are often used to protect online transactions.Digital certificates are issued by a trusted third party known as a certification authority (CA). The CA validates the identity of a certificate holder and “signs” the certificate to attest that it hasn’t been forged or altered in any way.New Uses For Digital CertificatesDigital certificates are now being used to provide security and validation for wireless connections, and hardware manufacturers are one of the latest groups to use them. Not long ago, Version Inc. announced its Cable Modem Authentication Services, which allow hardware manufacturers to embed digital certificates into cable modems to help prevent the pirating of broadband services through device cloning.Using Version software, hardware makers can generate cryptographic keys and corresponding digital certificates those manufacturers or cable service providers can use to automatically identify individual modems.This ‘ast-mile’authentication not only protects the value of existing content and services but also positions cable system operators to bring a broad new range of content, applications and value-added services to market.When a CA digitally signs a certificate, its owner can use it as an electronic passport to prove his identity. It can be presented to Web sites, networks or individuals that require secure access.Identifying information embedded in the certificate includes the holder’ s name and e-mail address, the name of the CA, a serial number and any activation or expiration data for the certificate. When the CA verifies a user’s identity, the certificate uses the holder’s public encryption key to protect this data.Certificates that a Web server uses to confirm the authenticity of a Web site for a user’s browser also employ public keys. When a user wants to send confidential information to a Web server, such as a credit-card number for an online transaction, the browser will access the public key in the server’s digital certificate to verify its identity.Role of Public-Key CryptographyThe public key is one half of a pair of keys used in public-key cryptography, which provides the foundation for digital certificates.Public-key cryptography uses matched public and private keys for encryption and decryption. These keys have a numerical value that’s used by an algorithm to scramble information and make it readable only to users with the corresponding decryption key.Others to encrypt information meant only for that person use a person’s public key. When he receives the information, he uses his corresponding private key, which is kept secret, to decrypt the data. A person's public key can be distributed without damaging the private key. A Web server using a digital certificate can use its private key to make sure that only it can decrypt confidential information sent to it over the Internet.The Web serve r’s certificate is validated by a self-signed CA certificate that identifies the issuing CA. CA certificates are preinstalled on most major Web browsers, including Microsoft Internet Explorer and Netscape Navigator.The CA certificate tells users whether they can trust the Web server certificate when it’s presented to the browser. If the validity of the Web server certificate is affirmed, the certificate’s public key is used to secure information for the server using Secure Sockets Layer (SSL) technology.Digital certificates are used by the SSL security protocol to create a secure “pipe” between two parties that seek confidential communication. SSL is used in most major Web browsers and commercial Web servers.3. Digital Wallets----A digital wallet is software that enables users to pay for goods on the Web ．It holds credit-card numbers and other personal information such as a shipping address ．Once entered，the data automatically populates order fields at merchant sites ．----When using a digital wallet，consumers don’t need to fill out order forms on each site when they purchase an item because the information has already been stored and is automatically updated and entered into the order fields across merchant sites ．Consumers also benefit when using digital wallets because their information is encrypted or protected by a private software code ．And merchants benefit by receiving protection against fraud ．----Digital wallets are available to consumers free of charge，and they’re fairly easy to obtain ．For example，when a consumer makes a purchase at a merchant site that’s set up to handle server-side digital wallets，he types his name and payment and shipping information into the merchant’s own form ．At the end of the purchase，one consumer is asked to sign up for a wallet of his choice by entering a user name and password for future purchases ．Users can also acquire wallets at a wallet vendor’s site ．----Although a wallet is free for consumers，vendors charge merchants for wallets ．----Digital wallets come in two main types: client-side and server- side ．Within those divisions are wallets that work only on specific merchant sites and those that are merchant agnostic ．----Client-based digital wallets，the older of the two types，are falling by the wayside，according to analysts，because they require users to download and install software ．A user downloads the wallet application and inputs payment and mailing information ．At that point，the information is secured and encrypted on the user’s hard drive ．The user retains control of his credit card and personal information locally ．----With a server-based wallet，a user fills out his personal information，and a cookie is automatically downloaded ．(A cookie is a text file that contains information about the user ．）In this scenario，the consumer information resides on the server of a financial institution or a digital wallet vendor rather than on the user’s PC ．----Server-side wallets provide assurance against merchant fraud because they use certificates to verify the identity of all parties ．When a party makes a transaction，it presents its certificate to the other parties involved ．A certificate is an attachment to an electronic message used to verify the identity of the party and to provide the receiver with the means to encode a reply ．----Furthermore，the cardholder’s sensitive data is typically housed at a financial institution，so there’s an extra sense of security because financial environments generally provide the highest degree of security ．----But even though wallets provide easy shopping online，adoption hasn’t been widespread ．----Standards are pivotal to the success of digital wallets ．----Last month，major vendors，including Microsoft Corp ．，Sun Microsystems Inc ．and America Online Inc ．announced their endorsement of a new standard called EMCL，or E-Commerce Modeling Language，to give Web merchants a standardized way to collect electronic data for shipping，billing and payment ．4. Grid StorageDefinition: Grid storage, analogous to grid computing, is a new model for deploying and managing storage distributed across multiple systems and networks, making efficient use of available storage capacity without requiring a large, centralized switching system.A grid is, in fact, a meshed network in which no single centralized switch or hub controls routing. Grids offer almost unlimited scalability in size and performance because they aren’t constrained by the need for ever-larger central switches. Grid networks thus reduce component costs and produce a reliable and resilient structure.Applying the grid concept to a computer network lets us harness available but unused resources by dynamically allocating and deal locating capacity, bandwidth and processing among numerous distributed computers. A computing grid can span locations, organizations, machine architectures and software boundaries, offering power, collaboration and information access to connected users. Universities and research facilities are using grids to build what amounts to supercomputer capability from PCs, Macintoshes and Linux boxes.After grid computing came into being, it was only a matter of time before a similar model would emerge for making use of distributed data storage. Most storage networks are built in star configurations, where all servers and storage devices are connected to a single central switch. In contrast, grid topology is built with a network of interconnected smaller switches that can scale as bandwidth increases and continue to deliver improved reliability and higher performance and connectivity.Based on current and proposed products, it appears that a grid storage system should include the following:Modular storage arrays: These systems are connected across a storage network using serial ATA disks. The systems can be block-oriented storage arrays or network-attached storage gateways and servers.Common virtualization layer: Storage must be organized as a single logical pool of resources available to users.Data redundancy and availability: Multiple copies of data should exist across nodes in the grid, creating redundant data access and availability in case of a component failure.Common management: A single level of management across all nodes should cover the areas of data security, mobility and migration, capacity on demand, and provisioning.Simplified platform/management architecture: Because common management is so important, the tasks involved in administration should be organized in modularfashion, allowing the auto discovery of new nodes in the grid and automating volume and file management.Three Basic BenefitsApplying grid topology to a storage network provides several benefits, including the following:Reliability. A well-designed grid network is extremely resilient. Rather than providing just two paths between any two nodes, the grid offers multiple paths between each storage node. This makes it easy to service and replace components in case of failure, with minimal impact on system availability or downtime.Performance. The same factors that lead to reliability also can improve performance. Not requiring a centralized switch with many ports eliminates a potential performance bottleneck, and applying load-balancing techniques to the multiple paths available offers consistent performance for the entire network.Scalability. It’s easy to expand a grid network using inexpensive switches with low port counts to accommodate additional servers for increased performance, bandwidth and capacity. In essence, grid storage is a way to scale out rather than up, using relatively inexpensive storage building blocks.四、译文新技术的计算机网络摘要：21世纪是信息经济的时代，作为这个时代的代表技术，计算机网络技术将在非常快的速度发展很快，不断创造性地将进入人们的工作，学习和生活中深。
计算机专业毕业论文参考文献(精选115个最新)
计算机专业是计算机硬件与软件相结合、面向系统、更偏向应用的宽口径专业。
通过基础教学与专业训练，培养基础知识扎实、知识面宽、工程实践能力强，具有开拓创新意识，在计算机科学与技术领域从事科学研究、教育、开发和应用的高级人才。
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计算机专业毕业论文参考文献一：[1]王琨. Linux操作系统下的网络多媒体技术应用[D].西安电子科技大学,2001.[2]陆海波. 智能型掌上电脑（PDA）的研究与开发[D].电子科技大学,2001.[3]高玉金. WINDOWS环境下并行容错局域网的研究及实现[D].燕山大学,2000.[4]陈军. 分布式存储环境下并行计算可扩展性的研究与应用[D].中国人民解放军国防科学技术大学,2000.[5]王霜. 瓦楞纸箱CAD系统开发[D].四川大学,2000.[6]王茂均. 织带机智能监测管理系统研究[D].大连理工大学,2000.[7]郭朝华. 多处理器并行的星上计算机系统设计[D].中国科学院上海冶金研究所,2000.[8]刘胜. 拖拉机作业机组仿真试验台自动变速控制系统的研究[D].中国农业大学,2000.[9]陈新昌. 冷藏、保温汽车静态降温调温性能测试系统的研究[D].河南农业大学,2000.[10]毛鹏军. 智能化温室环境参数微机监控系统的设计研究[D].河南农业大学,2000.[11]史志存. 电子鼻及其应用研究[D].中国科学院电子学研究所,2000.[12]孟笛. 复合材料加筋板壳结构稳定性设计的可视化研究和实现[D].大连理工大学,2000.[13]刘鹏民. 涡街电磁流量计机理的研究与开发[D].北京化工大学,2000.[14]付岩. 通用脚本语言GSCRIPT设计与应用的研究[D].中国科学院研究生院（计算技术研究所）,2000.[15]石争浩. 《计算机组成原理》CAI及其多媒体课件实现技术研究[D].西安理工大学,2000.[16]姚彤. 农机销售管理信息系统的设计与开发[D].东北农业大学,2000.[17]吕康娟. 基于地理信息系统(GIS)的小流域综合治理规划的研究[D].东北农业大学,2000.[18]邱建民. 北工大研究生教育管理信息系统[D].北京工业大学,2000.[19]刘春明. 变电站电压无功控制装置实用技术研究[D].华北电力大学,2000.[20]刘力力. 计算机系统性能评测与分析[D].中国科学院研究生院（计算技术研究所）,2000.[21]宋蓬勃. 基于校园网的高校研究生教务管理系统[D].山东师范大学,2000.[22]陈永华. WebGIS三维可视化的研究[D].解放军信息工程大学,2000.[23]潘炜华. 新生隐球菌分子重组操作系统的建立及其荚膜相关基因的研究[D].第二军医大学,2000.[24]杨群生. 模糊联想记忆网络和模糊图象处理研究[D].华南理工大学,2000.[25]牛红军. 自动车辆定位系统的研究[D].西安理工大学,2000.[26]张志强. 网络环境下住房公积金管理信息系统的研究[D].华北电力大学,2000.[27]王笑风. 路面摊铺机械自动调平控制器的仿真测试器的研究[D].长安大学,2000.[28]黄晓华. 壁板铣床数控系统硬件结构的研究与开发[D].大连理工大学,2000.[29]景玲玲. 河南省公路地理信息系统的研制与开发[D].大连理工大学,2000.[30]李吉宽. 单片机模糊控制在船舶电站自动并车中的应用[D].大连海事大学,2000.计算机专业毕业论文参考文献二：[31]徐洪禹. 面向只读应用的分布式数据库的模型构造及查询优化的研究[D].大连理工大学,2000.[32]李卫东. 微机控制LED点阵显示屏[D].大连理工大学,2000.[33]常天海. 希望-IV型多媒体语音教室系统的研究与设计[D].大连理工大学,2000.[34]解宏基. 变频调速矢量控制交流三相异步电动机的仿真研究[D].大连海事大学,2000.[35]宋东方. 基于公路养护管理的GIS应用与开发[D].大连理工大学,2000.[36]王晓丽. 工程图扫描输入与智能识别技术的研究[D].大连理工大学,2000.[37]田宇. 基于客户机/服务器的大连市血液中心管理信息系统[D].大连理工大学,2000.[38]杨敬辉. 基于Intranet的大连市血液中心管理信息系统[D].大连理工大学,2000.[39]任彬. 一种新型的水表联网抄表系统[D].大连理工大学,2000.[40]童晨涛. 港口调度现代信息网络的研究[D].大连海事大学,2000.[41]李德良. 基于寄生传输的检测报警系统[D].大连理工大学,2000.[42]侯宗浩. 集成C/S、B/S结构的物资采供系统研究[D].西安理工大学,2000.[43]雷晓强. 冗余度机器人的轨迹规划与障碍物回避的实时控制[D].西安理工大学,2000.[44]徐前锋. 多模型优化模糊控制算法的应用研究[D].西安理工大学,2000.[45]杨沂. 基于Intranet的电力综合管理信息系统分析与设计及用户满意度评价方法的研究[D].西安理工大学,2000.[46]张怀领. 异构环境下的分布式数据库事务处理的研究与实践[D].大连理工大学,2000.[47]王振华. 近海结构基础设计程序系统[D].大连理工大学,2000.[48]王琳. 基于软计算的智能控制器的研究[D].大连海事大学,2000.[49]何志刚. 基于Internet/Intranet技术的MIS应用与开发[D].大连海事大学,2000.[50]刘中兵. 焊缝图象识别的研究及应用[D].大连理工大学,2000.[51]崔鸿远. 玉米播种机工况监测系统的研究与试验[D].中国农业大学,2000.[52]田健. 超音频感应加热电源的研制[D].西安理工大学,2000.[53]祝华军. 小城镇规划及基础设施投资问题研究[D].中国农业大学,2000.[54]孙毅. 渭河洪水错峰调度决策支持系统[D].西安理工大学,2000.[55]张寿桂. 厦门港集装箱运输MIS总体规划研究[D].大连海事大学,2000.[56]王涛. 船舶管理信息系统的研究[D].大连海事大学,2000.[57]杨媛. 智能化超声波水流量计的理论分析与软件开发[D].西安理工大学,2000.[58]史庆国. 壁面机器人路径规划与控制系统研究[D].河北工业大学,2000.[59]田永青. 模糊控制系统的结构化分析[D].河北工业大学,2000.[60]丁承君. 基于神经网络和模糊控制的移动机器人墙跟踪[D].河北工业大学,2000.计算机专业毕业论文参考文献三：[61]周颖. 基于模糊滑动面的滑动模态控制方法研究[D].河北工业大学,2000.[62]张建华. 集中供热系统的水力计算及地理信息系统的开发[D].华北电力大学,2000.[63]徐延明. 地理信息系统在配电管理系统中的应用研究[D].华北电力大学,2000.[64]于成. 综合船舶信息处理与显示系统[D].大连海事大学,2000.[65]苏利敏. 新型串级调速系统的研究[D].河北工业大学,2000.[66]刘丽华. 大功率超声发生器的研制及超声乳化的实验研究[D].华北电力大学,2000.[67]孙东卫. 都江堰水利自动化控制系统设计[D].电子科技大学,1999.[68]胡霞光. 青藏公路CAE系统的研究与开发[D].长安大学,1999.[69]尹宏宾. 智能化信号交叉口控制及其交通量预测方法的研究[D].华南理工大学,1999.[70]邱焕耀. 模糊控制、神经网络和变结构控制的交叉结合及其应用研究[D].华南理工大学,1999.[71]张星明. 地质图象处理算法的研究与实现[D].中国科学院研究生院（计算技术研究所）,1999.[72]孟小峰. 中文数据库自然语言查询处理研究[D].中国科学院研究生院（计算技术研究所）,1999.[73]王灏. 机器人智能控制方法研究[D].华南理工大学,1999.[74]庄圣贤. 无传感速度伺服矢量变频调速系统的研究[D].电子科技大学,1999.[75]王伟. 序列图象的几何约束及其应用[D].西安电子科技大学,1998.[76]张光海. 受限柔性机器人装置、建模与控制的研究[D].华南理工大学,1998.[77]金菊良. 遗传算法及其在水问题中的应用[D].河海大学,1998.[78]樊晓平. 受限柔性机器人的动力学建模与智能控制[D].华南理工大学,1998.[79]黄道平. 多变量非线性过程控制[D].华南理工大学,1998.[80]陈虔. 大型应用软件协同开发的版本控制和管理—面向组件增量的版本控制方法[D].中国科学院研究生院（高能物理研究所）,1997.[81]刘黎临. 大型信息网络设计与性能研究[D].中国科学院研究生院（计算技术研究所）,1998.[82]牟树波. ACPI标准的实现技术[D].中国科学院研究生院（计算技术研究所）,1998.[83]侯春海. 工程中时延动态系统的定量稳定性分析[D].浙江大学,1997.[84]孙富春. 机械手的神经网络稳定自适应控制[D].清华大学,1997.[85]周勇. 遥感和地理信息系统支持的土水资源分类、评价与预测研究[D].华中农业大学,1997.[86]李明. 基于工作站网络的分布式共享存储系统的设计[D].中国科学院研究生院（计算技术研究所）,1997.[87]王晓鸥. 计算机控制短波自适应通信网的实现[D].中国科学院研究生院（计算技术研究所）,1997.[88]周小佳. 电力系统可靠性人工神经网络模型及实现研究[D].重庆大学,1997.[89]李永树. 地表移动预计方法及信息处理（SPDP）系统研究[D].中国矿业大学（北京）,1997.[90]孙毓忠. 互连网络性能分析及其应用[D].中国科学院研究生院（计算技术研究所）,1997.计算机专业毕业论文参考文献四：[91]马森. 曙光2000单一系统映象文件系统COSMOS操作系统相关层的设计和实现[D].中国科学院研究生院（计算技术研究所）,1997.[92]陈晨风. 高性能交流伺服系统的智能控制策略[D].浙江大学,1997.[93]林峰. 交流传动系统的控制策略[D].浙江大学,1997.[94]陈小红. 径向基函数网络及其在非线性控制中的应用[D].浙江大学,1996.[95]陈晓青. 高性能交流伺服系统的研究与开发[D].浙江大学,1996.[96]周宏甫. 六坐标工具磨床CNC系统的关键技术研究[D].华中理工大学,1996.[97]王杰. 高精度交流伺服系统的新型控制策略[D].浙江大学,1996.[98]金连文. 手写体汉字识别的研究[D].华南理工大学,1996.[99]戴建荣. 胶片剂量仪软件开发及其在X线立体定向放疗技术中的应用[D].中国协和医科大学,1996.[100]张虹. 并行计算机系统的用户界面研究与设计[D].中国科学院研究生院（计算技术研究所）,1996.[101]朱群雄. 神经网络结构理论与技术的研究及其在过程模拟与过程控制中的应用[D].北京化工大学,1996.[102]张朝海. 电力系统运行与控制[D].华南理工大学,1996.[103]侯昭胤. 神经网络辅助丙烷氨氧化催化剂设计[D].浙江大学,1996.[104]毕立群. 换热网络智能综合方法的理论研究与实践[D].北京化工大学,1995.[105]韦巍. 学习控制及其在机器人控制中的应用[D].浙江大学,1994.[106]金毅. 模糊集合论在生产计划和调度中的应用研究[D].东南大学,1994.[107]蒋其友. 人工智能理论与技术的研究及其在大型离心式压缩机故障诊断中的应用[D].北京化工大学,1993.[108]黄崇福. 信息扩散原理与计算思维及其在地震工程中的应用[D].北京师范大学,1992.[109]贾家麟. 城市环境工程地质系统工程分析方法及其应用[D].中国地质科学院,1992.[110]杨冀宏. 人工智能技术在分离过程综合中的应用研究[D].北京化工大学,1990.[111]钟勇. 人体胚胎视交叉微血管的实验研究[D].中国协和医科大学,1990.[112]赵一举. 肺动脉高压辅助诊断[D].中国协和医科大学,1989.[113]严晓光. 胶鞋模具CAD/CAM一体化技术的研究[D].华中理工大学,1988.[114]陈申. 连续搅拌反应釜（CSTR）计算机实时控制[D].浙江大学,1988.[115]朱善安. 电液控制系统辨识及实时控制策略研究[D].浙江大学,1987.以上就是关于计算机专业毕业论文参考文献的分享，希望对你有所帮助。
计算机网络技术英语作文
计算机网络技术英语作文英文回答：Computer networking is a rapidly evolving field thathas revolutionized the way we communicate, share information, and access resources. With the advent of the Internet, computer networks have become an essential partof our daily lives, enabling global connectivity,information dissemination, and collaboration on an unprecedented scale.The fundamental components of a computer networkinclude computers, networking devices (such as routers and switches), and communication media (such as cables or wireless connections). These components are interconnectedto form a network topology, which defines the physical and logical layout of the network. Different network topologies, such as star, bus, and ring topologies, have varying advantages and disadvantages, and the choice of topology depends on factors such as network size, performancerequirements, and cost.Data transmission over computer networks is governed by a set of protocols that define how data is formatted, addressed, transmitted, and received. The most widely used protocol suite is the Internet Protocol Suite (TCP/IP), which provides a reliable and efficient framework for communication across different types of networks. TCP/IP consists of several layers, each with its own specific responsibilities, such as data encapsulation, routing, and error checking.Network security is of paramount importance in protecting data from unauthorized access and attacks. Various security measures are employed to safeguard networks, including firewalls, intrusion detection systems, encryption, and authentication mechanisms. Network security best practices involve regularly updating software, implementing strong passwords, and conducting security audits to identify and mitigate vulnerabilities.Computer networks have had a profound impact on varioussectors, including education, healthcare, business, and entertainment. In education, computer networks facilitate remote learning, provide access to vast online educational resources, and enable collaboration among students and educators. In healthcare, computer networks allow for electronic health records, telemedicine, and remote monitoring of patients. In business, computer networks enable seamless communication and collaboration among employees, enhance efficiency through automation, and facilitate e-commerce. In entertainment, computer networks provide access to streaming services, online gaming, and social networking platforms.As technology continues to advance, computer networks will continue to evolve and play an even more integral role in our lives. The rise of mobile computing, cloud computing, and the Internet of Things (IoT) is driving the development of new network architectures and technologies to meet the increasing demands for connectivity, bandwidth, and security.中文回答：计算机网络技术。
关于计算机的英文文献
关于计算机的英文文献以下是一些关于计算机的英文文献：1. "Computer Science: The Discipline" by David Gries and Fred B. Schneider, published in 1993 in the journal Communications of the ACM.2. "The Art of Computer Programming" by Donald E. Knuth, published in three volumes between 1968 and 1973.3. "A Mathematical Theory of Communication" by Claude Shannon, published in 1948 in the Bell System Technical Journal.4. "Operating Systems Design and Implementation" by Andrew S. Tanenbaum and Albert S. Woodhull, published in 1997.5. "The Structure and Interpretation of Computer Programs" by Harold Abelson and Gerald Jay Sussman, published in 1984.6. "Computer Networks" by Andrew S. Tanenbaum, published in 1981.7. "Introduction to Algorithms" by Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest, and Clifford Stein, published in 1990.8. "Foundations of Computer Science" by Alfred Aho and Jeffrey Ullman, published in 1992.9. "Computer Architecture: A Quantitative Approach" byJohn L. Hennessy and David A. Patterson, first published in 1990.10. "Artificial Intelligence: A Modern Approach" by Stuart Russell and Peter Norvig, first published in 1995.。
计算机外文文献
计算机外文文献外文文献Computer network virus and precautionsWith the new network technology and application of the continuous rapid development of the computer network should Use of becoming increasingly widespread, the role played by the increasingly important computer networks and human More inseparable from the lives of the community's reliance on them will keep growing. With the continuous development of computer technology, the virus has become increasingly complex and senior, the new generation of computer viruses make full use of certain commonly used operating systems and application software for protection of the weak low spots have rampant in recent years as the popularity of the Internet in the world, will be attached document containing the virus the situation in the mail has been increasingspread of the virus through the Internet, making the spread of the virus speed Sharp also increased, by an ever-increasing scope of the infection. Therefore, the protection of the security of computer networks will become increasingly important.First,a computer virusA computer virus the definition of computer virus computer virus (Computer Virus) in the "people's republic of China the computer information system security protection regulations "which has beenclearly defined, the virus" refers to the preparation or computerprogram inserted in the damage or destruction of computer data functions, affecting computer use Self-replication and can a group of computer instructions, or code. "Second, network virusWith the development of network and the Internet, a wider spread,the greater New harm the virus emerged this is the Internet virus. The virus is an emerging concept in the traditional the virus was not classified network virus this concept, because the development of networks, the traditional virus the network also has a number of characteristics. Today's Internet virus is a broad notion of as a longas it is carried out using the Internet to spread destruction can be known as network viruses, such as: "Love the back door", "Panda burning incense."Third, network virus and the distinction between computer virusThe original common computer virus is nothing more than the devastating formatted hard drive, delete system with the users documents, databases, etc.destruction. The mode of transmission is through nothing but also by virus infection mutual copy of the software, carrying the virus, such as the use of pirated optical discs, such as infection disk systems the pilot virus and infected executable file virus, in addition to a network virus these are the common characteristics of the virus,but also steal users with remote data, remote control of the other side computers and other damaged properties, such as Trojan and consumptionof funding the operation of the network computer source collapse of the network server worm.Fourth, the network against virusNetwork destructive virus, will directly affect the work of the network, ranging from lowering speed video ring for the efficiency of the network, while in the collapse, undermining the server information to a multi-year work destroyed Dan. Because viruses and other network annually fraud led to economic losses of over 16 billion yuan, But this figure is constantly rising year by year. The next few years, the size of the market will reach Security 60 billion yuan. One antivirus software experts pointed out: "Network avian flu virus even more." Such as: "Xiong Cat burning incense "In addition to virus infection through the web site users, the latest virus also through QQ Loopholes in propagating itself through file-sharing networks, the default sharing, weak password systems, U disk and windows forms bottom of the top mobile hard drives, and other means of communication. While LAN once a computer machine for infection, it can spread through the entire network instant, or even within a very short period of time can be infected thousands of computers, can lead to serious networks. Symptoms of poisoning in the performance of computers there are enforceable. Exe files have become a strange pattern, the pattern shown as "Panda Burning incense, "and then System blue screen, restart the frequent, hard drive data destruction, serious entire company all computer LAN will all poisoning. "Panda burning incense," only more than half a month, a few varieties have highof more than 50, and the number of its users infected constantly expanding. Makes infected, "Panda burn incense" disease the personaldrug users has been as high as several million people infected with afew more corporate users is rising exponentially. Network more on the computer network the greater the harm caused by the virus.Fifth, Network transmission of the virus Features1. Infection fast: single machine environment, the virus can only be passed fromone computer diskette to another, and in the network can be adoptedby the rapid spread of network communication mechanism. According to measurement set against a typical PC network use in normal circumstances, once a computer workstation sick drugs, and will be online within 10 minutes in the several hundreds of all infected computers.2. Proliferation of a wide range: in the network due to the spreadof the virus very quickly and spread to encompass a large area, not only the rapid transmission of all LAN computer, but also through remote workstations virus in moment inter spreadto thousands of miles away.3. Dissemination in the form of complex and varied: computer viruses in general through the network " Station server workstation "channels of communication, but in the form of complex and diverse communication.4. Difficult to completely wipe: the standalone computer viruscarriers sometimes can be deleted documents or low-level formatted drives, and other measures to eliminate the virus completely, and thenetwork once a computer work clean stations failed to disinfect the entire network can be re-infected by the virus, or even just completed removal the work of a workstation is likely to be on-line by another workstation virus infection. Therefore, Only workstations in addition to killing viruses, and can not solve the virus harm to the network is.中文译文计算机网络病毒与防范随着各种新的网络技术的不断应用和迅速发展, 计算机网络的应用范围变得越来越广泛, 所起的作用越来越重要, 计算机网络与人类的生活更加密不可分, 社会对其的依赖程度也会随之不断增长。
计算机网络论文
计算机网络论文Title: The Impact of Computer Networks on Modern Society。
Introduction。
In the past few decades, computer networks have become an integral part of modern society. From communication to business operations, the impact of computer networks is undeniable. This paper aims to explore the various ways in which computer networks have influenced and shaped modern society.Communication。
One of the most significant impacts of computer networks is on communication. With the advent of the internet and social media platforms, people can now communicate with each other across the globe in real-time. This has revolutionized the way we interact with each other, making the world a smaller and more connected place. Additionally, the rise of email and instant messaging has transformed the way we communicate in both personal and professional settings.Business Operations。
英文文献及翻译：Internet的历史（2466字）（全文5篇）
英文文献及翻译：Internet的历史（2466字）（全文5篇）第一篇：英文文献及翻译：Internet的历史(2466字)英文资料翻译译文Internet的历史起源——ARPAnet Internet是被美国政府作为一项工程进行开发的。
这项工程的目的，是为了建立远距离之间点与点的通信，以便处理国家军事范围内的紧急事件，例如核战争。
这项工程被命名为ARPAnet，它就是Internet的前身。
建立此工程的主要应用对象就是军事通讯，那些负责ARPAnet的工程师们当时也没有想到它将成为“Internet”。
根据定义，一个“Internet”应该由四或者更多的计算机连接起来的网络。
ARPAnet是通过一种叫TCP/IP的协议实现连网工作的。
此协议最基础的工作原理是：如果信息在网络中的一条路径发送失败，那么它将找到其他路径进行发送，就好象建立一种语言以便一台计算机与其他计算机“交谈”一样，但不注意它是PC，或是Macintosh。
到了20世纪80年代，ARPAnet已经开始变成目前更为有名的Internet了，它拥有200台在线主机。
国防部很满意ARPAnets的成果，于是决定全力将它培养为能够联系很多军事主机，资源共享的服务网络。
到了1984年，它就已经超过1000台主机在线了。
在1986年ARPAnet关闭了，但仅仅是建立它的机构关闭了，而网络继续存在与超过1000台的主机之间。
由于使用NSF连接失败，ARPAnet才被关闭。
NSF是将5个国家范围内的超级计算机连入ARPAnet。
随着NSF的建立，新的高速的传输介质被成功的使用，在1988年，用户能通过56k的电话线上网。
在那个时候有28，174台主机连入Internet。
到了1989年有80，000台主机连入Internet。
到1989年末，就有290，000台主机连入了。
另外还有其他网络被建立，并支持用户以惊人的数量接入。
于1992年正式建立。
外文文献-计算机网络安全和防范
附录一翻译Computer network security and to guard againstAbstract: When mankind entered the 21st century information society, the network society of the time, China will establish a complete set of network security system, especially from the policy and law to establish China's own characteristics, network security system.Key words: computer; network; security; preventIn the information age, information can help groups or individuals so that they benefit from, the same information can also be used to pose a threat to them, caused damage. Therefore network security, including the composition of network hardware, software and network transmission of information security, so that they do not because of accidental or malicious destruction of the attacks, network security not only the technical aspects, but also management issues, both complement each other, are indispensable.First, the concept of computer network securityInternational Organization for Standardization of "computer security" is defined as: "To establish a data processing system and the adoption of technology and management of security protection, the protection of computer hardware, software, data is not due to accidental and malicious destruction of reasons, change and leakage." The above definition of computer security includes physical security and logical security of both the contents of the contents of the logic of security could be understood as we often say that the information security, information refers to the confidentiality, integrity and availability of protection, and network security Information security is the meaning of the extension, that network security is a network of information confidentiality, integrity and availability protection. Computer network security as the specific meaning of the user changes, the user isdifferent on the network security awareness and requirements will be different. From the ordinary user's point of view, could only hope that personal privacy or confidential information transmission on the network be protected against eavesdropping, tampering and forgery; and network provider in addition to care about these network information security, we must also consider how to deal with sudden natural disasters, such as military strikes against the destruction of network hardware, as well as unusual in the network how to restore network communications, and maintain the continuity of network communications.In essence, the network security, including the composition of network hardware, software and network transmission of information security, so that they do not because of accidental or malicious attacks on the destruction of both the technical aspects of network security issues, there are management issues, the two sides complement each other, are indispensable. Man-made network intrusion and attacks makes network security is facing new challenges.Second, computer network security status quoComputer network security is the network hardware, software and data systems are protected from accidental or malicious destruction of reasons, alteration, disclosure, the system continuous, reliable, normal operation of network services without disruption. Computer and network technology has the complexity and diversity, makes computer and network security has become a need to continue to update and improve the area. At present, hackers method has been more than the type of computer virus, and many attacks are fatal. In the Internet network, because the Internet does not have the time and geographical constraints, whenever there is a means to generate new attacks, we can in a week around the world, these attacks means the use of network and system vulnerabilities to attack computer systems and resulting in network paralysis. Worms, backdoor (Back-doors), Rootkits, DOS (DenialofServices) and Sniffer (network monitor) is a familiar means of several hacker attacks. However, none of these attacks means they reflect the astonishing power of today become worse. These types of attacks means the new variant, with previousattacks appeared methods, more intelligent, targeted against Internet-based protocols and operating system level. From the Web process control procedures to the kernel-level Rootlets. Hackers practices escalating renovation, to the user's ability to guard against information security challenge.Third, computer network security precautions1, to strengthen the internal network management and the use of safety awareness among staff, many computer systems commonly used passwords to control access to system resources, which is anti-virus process, the most vulnerable and the most economical methods. Network administrator and terminal operator privileges in accordance with their responsibilities, choose a different password for the application data legitimate operation, to prevent unauthorized users to access the data and the use of network resources.On the network, software installation and management is crucial, it is not only related to network maintenance and management efficiency and quality, but also to the network security. A good antivirus software can be easily installed within minutes to the organization each NT server can also be downloaded and spread to all the purpose of the machine by the network administrator set up and manage to focus, it will work with the operating system and other security is closely linked to become a part of network security management, and automatically provide the best network virus defensive measures. When the computer virus on-line resources applications attack, such as the virus exists in the information-sharing network of media, it is necessary to the security at the gateway, on the network front-end for antivirus.2, network firewall technologyIs a kind of used to strengthen the network access control to prevent the external network users to illegal means to enter the external network through the internal network, access internal network resources and protect the internal network operating environment special for Network Interconnection Devices. It is between two or more networks such as packet transmission link in accordance with a certain degree of security strategy to implement the inspection, to determine whether thenetwork communication between are allowed to, and monitor the network running. Although the firewall is to protect the network from an effective means of hacking, but there are obviously inadequate: through the firewall can not protect against outside attack other means, can not prevent defectors from the inside and inadvertent threats posed by users, but also can not completely prevent the transmission of the virus have been infected with the software or documents, and can not protect against data-driven attacks.3, security encryption technologyEncryption technology for the global e-commerce to provide a guarantee, so that Internet-based electronic trading system has become possible, thus improving the symmetric encryption and asymmetric encryption technology is still the mainstream of the 21st century. Symmetric encryption to the conventional password-based technology, computing encryption and decryption operations use the same key. Asymmetric encryption, encryption key that is different from the decryption key, encryption keys are made public, anyone can use, only the decryption key to decrypt people know.4, the network host operating system security and physical security measures Network firewall as the first line of defense and can not fully protect the internal network, must be combined with other measures to improve the safety of the system level. After the firewall is based on the network host operating system security and physical security measures. In accordance with the level from low to high, namely, the physical security of the host system, the core operating system security, system security, application services security and file system security; At the same time, host security checks and bug fixes, as well as a backup safety system as a supplementary safety measures. These constitute the entire network system, the second line of defense, the main part of a breakthrough to prevent the firewall as well as attacks from within. System backup is the last line of defense network system, used to attack after the System Restore. The firewall and host security measures is the overall system security by auditing, intrusion detection and response processor constitute the overall safety inspection and response measures. It from the networksystem firewall, network host or even directly from the network link layer on the extraction of network status information, as input to the intrusion detection subsystem. Intrusion Detection System in accordance with certain rules to determine whether there is any invasion of the incident, if the invasion occurred, the emergency treatment measures, and generate a warning message. Moreover, the system's security audit also can be used as the future consequences of aggressive behavior and to deal with security policy on the system to improve sources of information.In short, network security is a comprehensive issue, involving technology, management, use and many other aspects, including both its own information system security issues, there are physical and logical technical measures, a kind of technology can only solve the problem on the one hand, rather than a panacea. To this end the establishment of a network with Chinese characteristics, security system, the need for national policies and regulations to support and joint research and development group. Security and anti-security like two sides of contradictions, always pick-up, so the security industry is a future with the development of new technologies and the continuous development of industry.计算机网络安全和防范摘要：当人类跨入21世纪的信息社会，网络社会的时候，我国将建立一套完整的网络安全系统，特别是从政策和法律，建立我国自己的特点，网络安全系统。
计算机英文文献翻译
互联网的历史（1969－2009）1969: ArpanetArpanet was the first real network to run on packet switching technology (new at the time). On the October 29, 1969, computers at Stanford and UCLA connected for the first time. In effect, they were the first hosts on what would one day become the Internet.The first message sent across the network was supposed to be “Login”, but reportedly, the link between the two colleges crashed on the letter “g”.1970: Arpanet networkAn Arpanet network was established between Harvard, MIT, and BBN (the company that created the “interface message processor” computers used to connect to the network) in 1970.1971: EmailEmail was first developed in 1971 by Ray Tomlinson, who also made the decision to use the “@” symbol to separate the user name from the computer name (which later on became the domain name).1971: Project Gutenberg and eBooksOne of the most impressive developments of 1971 was the start of Project Gutenberg. Project Gutenberg, for those unfamiliar with the site, is a global effort to make books and documents in the public domain available electronically–for free–in a variety of eBook and electronic formats.It began when Michael Hart gained access to a large block of computing time and came to the realization that the future of computers wasn’t in computing itself, but in the storage, retrieval and searching of information that, at the time, was only contained in libraries. He manually typed (no OCR at the time) the “Declaration of Independence”and launched Project Gutenberg to make information contained in books widely available in electronic form. In effect, this was the birth of the eBook.1972: CYCLADESFrance began its own Arpanet-like project in 1972, called CYCLADES. While Cyclades was eventually shut down, it did pioneer a key idea: the host computer should be responsible for data transmission rather than the network itself.1973: The first trans-Atlantic connection and the popularity of emailingArpanet made its first trans-Atlantic connection in 1973, with the University College of London. During the same year, email accounted for 75% of all Arpanet network activity.1974: The beginning of TCP/IP1974 was a breakthrough year. A proposal was published to link Arpa-like networks together into a so-called “inter-network”, which would have no central control and would work around a transmission control protocol (which eventually became TCP/IP).1975: The email clientWith the popularity of emailing, the first modern email program was developed byJohn Vittal, a programmer at the University of Southern California in 1975. The biggest technological advance this program (called MSG) made was the addition of”Reply” and “Forward”functionality.1977: The PC modem1977 was a big year for the development of the Internet as we know it today. It’s the year the first PC modem, developed by Dennis Hayes and Dale Heatherington, was introduced and initially sold to computer hobbyists.1978: The Bulletin Board System (BBS)The first bulletin board system (BBS) was developed during a blizzard in Chicago in 1978.1978: Spam is born1978 is also the year that brought the first unsolicited commercial email message(later known as spam), sent out to 600 California Arpanet users by Gary Thuerk.1979: MUD – The earliest form of multiplayer gamesThe precursor to World of Warcraft and Second Life was developed in 1979, and was called MUD (short for MultiUser Dungeon). MUDs were entirely text-based virtual worlds, combining elements of role-playing games, interactive, fiction, and online chat.1979: Usenet1979 also ushered into the scene: Usenet, created by two graduate students. Usenet was an internet-based discussion system, allowing people from around the globe to converse about the same topics by posting public messages categorized by newsgroups.1980: ENQUIRE softwareThe European Organization for Nuclear Research (better known as CERN) launchedENQUIRE (written by Tim Berners-Lee), a hypertext program that allowed scientists at the particle physics lab to keep track of people, software, and projects using hypertext (hyperlinks).1982: The first emoticonWhile many people credit Kevin MacKenzie with the invention of the emoticon in 1979, it was Scott Fahlman in 1982 who proposed using aftera joke, rather than the original -) proposed by MacKenzie. The modern emoticon was born.1983: Arpanet computers switch over to TCP/IPJanuary 1, 1983 was the deadline for Arpanet computers to switch over to the TCP/IP protocols developed by Vinton Cerf. A few hundred computers were affected by the switch. The name server was also developed in ‘831984: Domain Name System (DNS)The domain name system was created in 1984 along with the first Domain Name Servers (DNS). The domain name system was important in that it made addresses on the Internet more human-friendly compared to its numerical IP address counterparts. DNS servers allowed Internet users to type in an easy-to-remember domain name and then converted it to the IP address automatically.1985: Virtual communities1985 brought the development of The WELL (short for Whole Earth‘Lectronic Link), one of the oldest virtual communities still in operation. It was developed by Stewart Brand and Larry Brilliant in February of ‘85. It started out as a community of the readers and writers of the Whole Earth Review and was an open but “remarkably literate and uninhibited intellectual gathering”. Wired Magazine once called The Well “The most influential online community in the world.”1986: Protocol warsThe so-called Protocol wars began in 1986. European countries at that time were pursuing the Open Systems Interconnection (OSI), while the United States was using the Internet/Arpanet protocol, which eventually won out.1987: The Internet growsBy 1987, there were nearly 30,000 hosts on the Internet. The original Arpanet protocol had been limited to 1,000 hosts, but the adoption of the TCP/IP standard made larger numbers of hosts possible.1988: IRC – Internet Relay ChatAlso in 1988, Internet Relay Chat (IRC) was first deployed, paving the way for real-time chat and the instant messaging programs we use today.1988: First major malicious internet-based attackOne of the first major Internet worms was released in 1988. Referred to as “The Morris Worm”, it was written by Robert Tappan Morris and caused major interruptionsacross large parts of the Internet.1989: AOL is launchedWhen Apple pulled out of the AppleLink program in 1989, the project was renamed and America Online was born. AOL, still in existence today, later on made the Internetpopular amongst the average internet users.1989: The proposal for the World Wide Web1989 also brought about the proposal for the World Wide Web, written by Tim Berners-Lee. It was originally published in the March issue of MacWorld, and then redistributed in May 1990. It was written to persuade CERN that a global hypertext system was in CERN’s best interest. It was originally called “Mesh”; the term “World Wide Web” was coined while Berners-Lee was writing the code in 1990.1990: First commercial dial-up ISP1990 also brought about the first commercial dial-up Internet provider, The World. The same year, Arpanet ceased to exist.1990: World Wide Web protocols finishedThe code for the World Wide Web was written by Tim Berners-Lee, based on his proposal from the year before, along with the standards for HTML, HTTP, and URLs.1991: First web page created1991 brought some major innovations to the world of the Internet. The first web pagewas created and, much like the first email explained what email was, its purpose was to explain what the World Wide Web was.1991: First content-based search protocolAlso in the same year, the first search protocol that examined file contents instead of just file names was launched, called Gopher.1991: MP3 becomes a standardAlso, the MP3 file format was accepted as a standard in 1991. MP3 files, being highly compressed, later become a popular file format to share songs and entire albums via the internet.1991: The first webcamOne of the more interesting developments of this era, though, was the first webcam. It was deployed at a Cambridge University computer lab, and its sole purpose was to monitor a particular coffee maker so that lab users could avoid wasted trips to an empty coffee pot.1993: Mosaic – first graphical web browser for the general publicThe first widely downloaded Internet browser, Mosaic, was released in 1993. While Mosaic wasn’t the first web browser, it is considered the first browser to make the Internet easily accessible to non-techies.1993: Governments join in on the funIn 1993, both the White House and the United Nations came online, marking the beginning of the .gov and .org domain names.1994: Netscape NavigatorMosaic’s first big competitor, Netscape Navigator, was released the year following (1994).1995: Commercialization of the internet1995 is often considered the first year the web became commercialized. While there were commercial enterprises online prior to ‘95, there were a few key developments that happened that year. First, SSL (Secure Sockets Layer) encryption was developed by Netscape, making it safer to conduct financial transactions (like credit card payments) online.In addition, two major online businesses got their start the same year. The first sale on “Echo Bay” was made that year. Echo Bay later became eBay. also started in 1995, though it didn’t turn a profit for six years, until 2001.1995: Geocities, the Vatican goes online, and JavaScriptOther major developments that year included the launch of Geocities (which officially closed down on October 26, 2009).The Vatican also went online for the first time.Java and JavaScript (originally called LiveScript by its creator, Brendan Eich, and deployed as part of the Netscape Navigator browser – see comments for explanation) was first introduced to the public in 1995. ActiveX was launched by Microsoft the following year.1996: First web-based (webmail) serviceIn 1996, HoTMaiL (the capitalized letters are an homage to HTML), the first webmail service, was launched.1997: The term “weblog” is coinedWhile the first blogs had been around for a few years in one form or another, 1997 was the first year the term “weblog” was used.1998: First new story to be broken online instead of traditional mediaIn 1998, the first major news story to be broken online was the Bill Clinton/Monica Lewinsky scandal (also referred to as “Monicagate” amongother nicknames), which was posted on The Drudge Report after Newsweek killed the story.1998: Google!Google went live in 1998, revolutionizing the way in which people find information online.1998: Internet-based file-sharing gets its rootsIn 1998 as well, Napster launched, opening up the gates to mainstream file-sharing of audio files over the internet.1999: SETI@home project1999 is the year when one of the more interesting projects ever brought online: theSETI@home project, launched. The project has created the equivalent of a giant supercomputer by harnessing the computing power of more than 3 million computers worldwide, using their processors whenever the screensaver comes on, indicating that the computer is idle. The program analyzes radio telescope data to look for signs of extraterrestrial intelligence.2000: The bubble bursts2000 was the year of the dotcom collapse, resulting in huge losses for legions of investors. Hundreds of companies closed, some of which had never turned a profit for their investors. The NASDAQ, which listed a large number of tech companies affected by the bubble, peaked at over 5,000, then lost 10% of its value in a single day, and finally hit bottom in October of 2002.2001: Wikipedia is launchedWith the dotcom collapse still going strong, Wikipedia launched in 2001, one of the websites that paved the way for collective web content generation/social media.2003: VoIP goes mainstreamIn 2003: Skype is released to the public, giving a user-friendly interface to Voice over IP calling.2003: MySpace becomes the most popular social networkAlso in 2003, MySpace opens up its doors. It later grew to be the most popular social network at one time (thought it has since been overtaken by Facebook).2003: CAN-SPAM Act puts a lid on unsolicited emailsAnother major advance in 2003 was the signing of the Controlling the Assault of Non-Solicited Pornography and Marketing Act of 2003, better known as the CAN-SPAM Act.2004: Web 2.0Though coined in 1999 by Darcy DiNucci, the term “Web 2.0″, referring to websites and Rich Internet Applications (RIA) that are highly interactive and user-driven became popular around 2004. During the first Web 2.0 conference, John Batelle and Tim O’Reilly described the concept of “the Web as a Platform”: software applications built to take advantage of internet connectivity, moving away from the desktop (which has downsides such as operating system dependency and lack of interoperability).2004: Social Media and DiggThe term “social media”, believed to be first used by Chris Sharpley, was coined in the same year that “Web 2.0″ became a mainstream concept. Social media–sites and web applications that allow its users to create and share content and to connect with one another–started around this period.Digg, a social news site, launched on November of 2004, paving the way for sites such as Reddit, Mixx, and Yahoo! Buzz. Digg revolutionized traditional means of generating and finding web content, democratically promoting news and web links that are reviewed and voted on by a community.2004: “The” Facebook open to college studentsFacebook launched in 2004, though at the time it was only open to college students and was called “The Facebook”; later on, “The” was dropped from the name, though the URL still works.2005: YouTube – streaming video for the massesYouTube launched in 2005, bringing free online video hosting and sharing to the masses.2006: Twitter gets twitteringTwitter launched in 2006. It was originally going to be called twittr (inspired by Flickr); the first Twitter message was “just setting up my twttr”.2007: Major move to place TV shows onlineHulu was first launched in 2007, a joint venture between ABC, NBC, and Fox to make popular TV shows available to watch online.2007: The iPhone and the Mobile WebThe biggest innovation of 2007 was almost certainly the iPhone, which was almost wholly responsible for renewed interest in mobile web applications and design.2008: “Internet Election”The first “Internet election” took place in 2008 with the U.S. Presidential election. It was the first year that national candidates took full advantage of all the Internet had to offer. Hillary Clinton jumped on board early with YouTube campaign videos. Virtually every candidate had a Facebook page or a Twitter feed, or both.Ron Paul set a new fundraising record by raising $4.3 million in a single daythrough online donations, and then beat his own record only weeks later by raising $4.4 million in a single day.The 2008 elections placed the Internet squarely at the forefront of politics and campaigning, a trend that is unlikely to change any time in the near future.2009: ICANN policy changes2009 brought about one of the biggest changes to come to the Internet in a long time when the U.S. relaxed its control over ICANN, the official naming body of the Internet (they’re the organization in charge of registering domain names).THE HISTORY OF THE INTERNETThe Beginning - ARPAnetThe Internet started as a project by the US government. The object of the project was to create a means of communications between long distance points, in the event of a nation wide emergency or, more specifically, nuclear war. The project was called ARPAnet, and it is what the Internet started as. Funded specifically for military communication, the engineers responsible for ARPANet had no idea of the possibilities of an "Internet."By definition, an 'Internet' is four or more computers connected by a network.ARPAnet achieved its network by using a protocol called TCP/IP. The basics around this protocol was that if information sent over a network failed to get through on one route, it would find another route to work with, as well as establishing a means for one computer to "talk" to another computer, regardless of whether it was a PC or a Macintosh.By the 80's ARPAnet, just years away from becoming the more well known Internet, had 200 computers. The Defense Department, satisfied with ARPAnets results, decided to fully adopt it into service, and connected many military computers and resources into the network. ARPAnet then had 562 computers on its network. By theyear 1984, it had over 1000 computers on its network.In 1986 ARPAnet (supposedly) shut down, but only the organization shutdown, and the existing networks still existed between the more than 1000computers. It shut down due to a failied link up with NSF, who wanted toconnect its 5 countywide super computers into ARPAnet.With the funding of NSF, new high speed lines were successfully installedat line speeds of 56k (a normal modem nowadays) through telephone linesin 1988. By that time, there were 28,174 computers on the (by then decided) Internet. In 1989 there were 80,000 computers on it. By 1989, there were 290,000.Another network was built to support the incredible number of peoplejoining. It was constructed in 1992.Today - The InternetToday, the Internet has become one of the most important technological advancements in the history of humanity. Everyone wants to get 'on line' to experience the wealth of information of the Internet. Millions of people now use the Internet, and it's predicted that by the year 2003 every single person on the planet will have Internet access. The Internet has truly become a way of life in our time and era, and is evolving so quickly its hard to determine where it will go next, as computer and network technology improve every day.HOW IT WORKS:It's a standard thing. People using the Internet. Shopping, playing games,conversing in virtual Internet environments.The Internet is not a 'thing' itself. The Internet cannot just "crash." It functions the same way as the telephone system, only there is no Internet company that runs the Internet.The Internet is a collection of millioins of computers that are all connected to each other, or have the means to connect to each other. The Internet is just like an office network, only it has millions of computers connected to it.The main thing about how the Internet works is communication. How does a computer in Houston know how to access data on a computer in Tokyo to view a webpage?Internet communication, communication among computers connected to the Internet, is based on a language. This language is called TCP/IP. TCP/IP establishes a language for a computer to access and transmit data over the Internet system.But TCP/IP assumes that there is a physical connecetion between one computer and another. This is not usually the case. There would have to be a network wire that went to every computer connected to the Internet, but that would make the Internet impossible to access.The physical connection that is requireed is established by way of modems,phonelines, and other modem cable connections (like cable modems or DSL). Modems on computers read and transmit data over established lines,which could be phonelines or data lines. The actual hard core connections are established among computers called routers.A router is a computer that serves as a traffic controller for information.To explain this better, let's look at how a standard computer might view a webpage.1. The user's computer dials into an Internet Service Provider (ISP). The ISP might in turn be connected to another ISP, or a straight connection into the Internet backbone.2. The user launches a web browser like Netscape or Internet Explorer and types in an internet location to go to.3. Here's where the tricky part comes in. First, the computer sends data about it's data request to a router. A router is a very high speed powerful computer running special software. The collection of routers in the world make what is called a "backbone," on which all the data on the Internet is transferred. The backbone presently operates at a speed of several gigabytes per-second. Such a speed compared to a normal modem is like comparing the heat of the sun to the heat of an ice-cube.Routers handle data that is going back and forth. A router puts small chunks of data into packages called packets, which function similarly to envelopes. So, when the request for the webpage goes through, it uses TCP/IP protocols to tell the router what to do with the data, where it's going, and overall where the user wants to go.4. The router sends these packets to other routers, eventually leading to the target computer. It's like whisper down the lane (only the information remains intact).5. When the information reaches the target web server, the webserver then begins to send the web page back. A webserver is the computer where the webpage is stored that is running a program that handles requests for the webpage and sends the webpage to whoever wants to see it.6. The webpage is put in packets, sent through routers, and arrive at the users computer where the user can view the webpage once it is assembled.The packets which contain the data also contain special information that lets routers and other computers know how to reassemble the data in the right order.With millions of web pages, and millions of users, using the Internet is not always easy for a beginning user, especially for someone who is not entirely comfortale with using computers. Below you can find tips tricks and help on how to use main services of the Internet.Before you access webpages, you must have a web browser to actually be able to view the webpages. Most Internet Access Providers provide you with a web browser in the software they usually give to customers; you. The fact that you are viewing this page means that you have a web browser. The top two use browsers are Netscape Communicator and Microsoft Internet Explorer. Netscape can be found at and MSIE can be found at /ie.The fact that you're reading this right now means that you have a web browser.Next you must be familiar with actually using webpages. A webpage is a collection of hyperlinks, images, text, forms, menus, and multimedia. To "navigate" a webpage, simply click the links it provides or follow it's own instructions (like if it has a form you need to use, it will probably instruct you how to use it). Basically,everything about a webpage is made to be self- explanetory. That is the nature of a webpage, to be easily navigatable."Oh no! a 404 error! 'Cannot find web page?'" is a common remark made by new web-users.Sometimes websites have errors. But an error on a website is not the user's fault, of course.A 404 error means that the page you tried to go to does not exist. This could be because the site is still being constructed and the page hasn't been created yet, or because the site author made a typo in the page. There's nothing much to do about a 404 error except for e-mailing the site administrator (of the page you wanted to go to) an telling him/her about the error.A Javascript error is the result of a programming error in the Javascript code of a website. Not all websites utilize Javascript, but many do. Javascript is different from Java, and most browsers now support Javascript. If you are using an old version of a web browser (Netscape 3.0 for example), you might get Javascript errors because sites utilize Javascript versions that your browser does not support. So, you can try getting a newer version of your web browser.E-mail stands for Electronic Mail, and that's what it is. E-mail enables people to send letters, and even files and pictures to each other.To use e-mail, you must have an e-mail client, which is just like a personal post office, since it retrieves and stores e-mail.Secondly, you must have an e-mail account. Most Internet Service Providers provide free e-mail account(s) for free. Some services offer free e-mail, like Hotmail, and Geocities.After configuring your e-mail client with your POP3 and SMTP server address (your e-mail provider will give you that information), you are ready to receive mail.An attachment is a file sent in a letter. If someone sends you an attachment and you don't know who it is, don't run the file, ever. It could be a virus or some other kind of nasty programs. You can't get a virus just by reading e-mail, you'll have to physically execute some form of program for a virus to strike.A signature is a feature of many e-mail programs. A signature is added to the end of every e-mail you send out. You can put a text graphic, your business information, anything you want.Imagine that a computer on the Internet is an island in the sea. The sea is filled with millions of islands. This is the Internet. Imagine an island communicates with other island by sending ships to other islands and receiving ships. The island has ports to accept and send out ships.A computer on the Internet has access nodes called ports. A port is just a symbolic object that allows the computer to operate on a network (or the Internet). This method is similar to the island/ocean symbolism above.Telnet refers to accessing ports on a server directly with a text connection. Almost every kind of Internet function, like accessing web pages,"chatting," and e-mailing is done over a Telnet connection.Telnetting requires a Telnet client. A telnet program comes with the Windows system, so Windows users can access telnet by typing in "telnet" (without the "'s) in the run dialog. Linux has it built into the command line; telnet. A popular telnet program for Macintosh is NCSA telnet.Any server software (web page daemon, chat daemon) can be accessed via telnet, although they are not usually meant to be accessed in such a manner. For instance, it is possible to connect directly to a mail server and check your mail by interfacing with the e-mail server software, but it's easier to use an e-mail client (of course).There are millions of WebPages that come from all over the world, yet how will you know what the address of a page you want is?Search engines save the day. A search engine is a very large website that allows you to search it's own database of websites. For instance, if you wanted to find a website on dogs, you'd search for "dog" or "dogs" or "dog information." Here are a few search-engines.1. Altavista () - Web spider & Indexed2. Yahoo () - Web spider & Indexed Collection3. Excite () - Web spider & Indexed4. Lycos () - Web spider & Indexed5. Metasearch () - Multiple searchA web spider is a program used by search engines that goes from page to page, following any link it can possibly find. This means that a search engine can literally map out as much of the Internet as it's own time and speed allows for.An indexed collection uses hand-added links. For instance, on Yahoo's site. You can click on Computers & the Internet. Then you can click on Hardware. Then you can click on Modems, etc., and along the way through sections, there are sites available which relate to what section you're in.Metasearch searches many search engines at the same time, finding the top choices from about 10 search engines, making searching a lot more effective.Once you are able to use search engines, you can effectively find the pages you want.With the arrival of networking and multi user systems, security has always been on the mind of system developers and system operators. Since the dawn of AT&T and its phone network, hackers have been known by many, hackers who find ways all the time of breaking into systems. It used to not be that big of a problem, since networking was limited to big corporate companies or government computers who could afford the necessary computer security.The biggest problem now-a-days is personal information. Why should you be careful while making purchases via a website? Let's look at how the internet works, quickly.The user is transferring credit card information to a webpage. Looks safe, right? Not necessarily. As the user submits the information, it is being streamed through a series of computers that make up the Internet backbone. The information is in little chunks, in packages called packets. Here's the problem: While the information is being。
computer network 计算机 网络 外文文献
PROCESS DESIGN AND CONTROLComputer-Aided Simulation Model for Natural Gas PipelineNetwork System OperationsPanote Nimmanonda,Varanon Uraikul,Christine W.Chan,andPaitoon Tontiwachwuthikul*Faculty of Engineering,University of Regina,Regina,Saskatchewan,Canada S4S0A2This paper presents the development of a computer-aided simulation model for natural gaspipeline network system operations.The simulation model is a useful tool for simulating andanalyzing the behavior of natural gas pipeline systems under different operating conditions.Historical data and knowledge of natural gas pipeline system operations are crucial informationused in formulating the simulation model.This model incorporates the natural gas properties,energy balance,and mass balance that lay the foundation of knowledge for natural gas pipelinenetwork systems.The user can employ the simulation model to create a natural gas pipelinenetwork system,selecting the components of natural gas,pipe diameters,and compressorcapacities for different seasons.Because the natural gas consumption rate continuously varieswith time,the dynamic simulation model was built to display state variables of the natural gaspipeline system and to provide guidance to the users on how to operate the system properly.The simulation model was implemented on Flash(Macromedia)and supports use of thesimulation model on the Internet.The model was tested and validated using the data from theSt.Louis East system,which is a subsystem of the natural gas pipeline network system ofSaskEnergy/Transgas Company.The model can efficiently simulate behaviors of the pipelinesystem with satisfactory validated results.1.IntroductionNatural gas is one of the most widely used sources of energy in North America,especially in Canada.Efficient operations of natural gas pipelines are important for ensuring gas transmission to customers.Construction of a natural gas pipeline network system can be difficult because of variations in customer consumption rates, which directly influence system properties such as the inline pressure and the volume of natural gas transmit-ted.These parameters also vary depending on the season.To better support the design of natural gas pipelines,constructing a model that can simulate the operational behaviors of the system is important.To construct a simulation model,historical and current observations collected on system behaviors are needed. Simulation models can provide predicted system behav-iors based on a number of“what if”scenarios about the real-world system.Some relevant works that describe the use of simulation models in industrial processes include the following:Simulations have been applied to different disciplines,including engineering,social science,and business by Banks.2A simulation model for the control of food freezing processes using a discrete dynamic technique with quantitative knowledge was proposed by Banoune and Depeyre.3A basic steady-state and dynamic simulation model in which every plant component was represented according to a graphical modeling technique was applied to a power plant system by Lu.10The main objective of this paper is to present the development of a computer-aided simulation model for natural gas pipeline network systems.Such a system can assist users in the design of a natural gas pipeline network system.The simulation model was designed to support the following tasks:(1)specifying the key components of a generic natural gas pipeline network system,(2)providing practical knowledge and a suitable mathematical model for the system,(3)helping users to construct a natural gas pipeline network system that models their real systems on the Internet,and(4) analyzing and predicting the behaviors of systems dynamically under changing conditions of operations. The model was implemented on Flash development software(Macromedia).Flash is an environment for designing and delivering low-bandwidth animations, presentations,and Web sites.It contains powerful multimedia capabilities and also offers scripting capa-bilities and server-side connectivity for creating interac-tive elements and Web applications.This paper is organized as follows:Section2presents an overview of the operations of a general natural gas pipeline network system,including the main compo-nents of the system and their characteristics.This section also explains how the characteristics of system components are formulated into a mathematical model. Section3describes the role of each component in the simulation model,including how the data are processed*To whom correspondence should be addressed.Tel.:(306)585-4160.Fax:(306)585-4855.E-mail:paitoon@uregina.ca.990Ind.Eng.Chem.Res.2004,43,990-100210.1021/ie030268+CCC:$27.50©2004American Chemical SocietyPublished on Web01/09/2004and the results generated.Section4describes a case study and how the graphical user interfaces are used. The data from the case study are integrated with the simulation model for testing.Section5discusses the results of the test,as well as their verification and validation.Finally,the conclusions and agenda for future work are given in section6.2.Natural Gas Pipeline Network SystemA natural gas pipeline system involves a set of operations and components that must be clearly under-stood before a simulation model can be built.2.1.Natural Gas Operations.The tasks of natural gas operations involve monitoring parameters of the pipeline system,determining customer demand for natural gas,and adjusting operations to meet demand. The main task of the dispatcher is to regulate compres-sors to control the pressure of natural gas in the system. Effective operation of the compressor is not easy,as there are many factors to consider and many compo-nents in the pipeline system.2.2.Main Components of Natural Gas Pipeline Network Systems.There are five main components in a natural gas pipeline network system:the natural gas,the pipeline network system,the compressor sta-tions,the customers,and the ambient temperature of gas.Each can affect the condition of the natural gas pipeline system in different ways.(1)Natural gas is mainly utilized for heating in households and industries.It is customarily defined as a mixture of gases,including both hydrocarbons and non-hydrocarbons.All hydrocarbon gases are character-ized by the general formula of C n H2n+2,and the non-hydrocarbon gases are nitrogen and carbon dioxide.The principal component in natural gas is methane(CH4), which does not condense to a liquid under any typical operating conditions.Normally,natural gas in a pipeline system contains85-95%methane,along with varying small proportions of ethane,propane,and butane and a maximum of about5%non-hydrocarbon components.15 If the composition in terms of percentages of the components should change,then the properties of the natural gas are also altered.(2)Pipeline network systems constitute an economical means of transporting fluid over long distances because they have low operating and capital costs,which decline further with larger volumes of throughput.Many factors are involved in the design of long-distance natural gas pipelines,including the type and diameter of pipes and the length of the pipelines.The type of pipe can affect the characteristics of natural gas operations.One of the main concerns is the roughness of the pipe,which directly affects the friction factor of a pipe.The fiction factor increases in proportion to the pipe’s roughness and is used to compute the magnitude of the pressure drop due to friction between the fluid and the surface of the pipe.The length of a pipeline is usually measured from one natural gas station to another,from a natural gas station to a customer area,or from one customer area to another.It is desirable for the pipe length to be minimized in order to reduce capital and operating costs.The diameter of a pipe can affect the volume of natural gas transmitted at a given natural gas velocity because pipes with larger diameters can transmit more natural gas than those with smaller ones.However,a pipe with a larger diameter also has a higher cost. Therefore,pipeline designers or engineers have to consider these factors in optimizing the capital and operating costs.(3)Compressor stations contain compressors for in-creasing,maintaining,and decreasing pressure in the pipeline system.In general,the compressors can gener-ate pressure to satisfy the demand of all customers in the pipeline system.(4)The type of customer is a key factor that affects the flow rate in the pipeline at a given time.Natural gas customers can be categorized into four types,i.e., residential,farming,commercial,and industrial,and each category of customers consumes natural gas at a different rate.For example,the demand of industrial customers is constant,whereas the demand of residen-tial customers fluctuates during different periods of time in a day.Statistically,the maximum consumption occurs in the mornings and evenings because the customers utilize natural gas for cooking and heating in the mornings and for heating houses and buildings in the evenings.(5)Ambient temperature affects customer consump-tion of natural gas;that is,the consumption rate varies depending on the season.In winter,customers consume more natural gas than they do in summer.The con-sumption rate usually hits the highest level in winter and the lowest level in summer.Meanwhile,in fall and spring,the consumption rate is at a moderate level.2.3.Natural Gas Properties.Natural gas properties are the basic considerations that provide the basis for calculating indicators of the state of a pipeline system such as the pressure and flow rate of the natural gas. Five natural gas properties are involved in the simula-tion model:molecular weight,gas gravity,compress-ibility factor,gas density,and viscosity.These properties are described as follows:Molecular Weight.Molecular weight can be deter-mined using eq1where M g is the overall molecular weight of the natural gas,M i is the molecular weight of each hydrocarbon or non-hydrocarbon component i,and y i is the mole fraction of each hydrocarbon or non-hydrocarbon component i. Gas Specific Gravity.In natural gas,specific grav-ity can be defined using eq2whereγg is the gas specific gravity,M g is the natural gas molecular weight,and M a is the air molecular weight.Compressibility Factor.To obtain the compress-ibility factor,the pseudo-reduced temperature(T r)and pressure(p r)must be first calculated using eqs3and 4,respectivelywhere T r is a pseudo-reduced temperature and p r is a pseudo-reduced pressure;T and p are the operating temperature and pressure,respectively;T c and p c are the critical temperature and pressure,respectively. To obtain the value of the critical temperature and pressure of a gas mixture,Key’s mixture rule can be applied to determine the pseudo-critical temperatureMg)∑y i M i(1)γg)Mg/Ma(2)Tr)T/Tc(3)pr)p/pc(4)Ind.Eng.Chem.Res.,Vol.43,No.4,2004991and pressure as followswhere T pc and p pc are the pseudo-critical temperature and pressure,respectively;y i is the mole fraction of each hydrocarbon or non-hydrocarbon component i;T c i and p c i are the critical temperature and pressure,respec-tively,of each component i.Table1provides the values of molecular weight, critical pressure,and critical temperature of the hydro-carbon and non-hydrocarbon components of natural gas.4In practice,a Standing and Katz chart is used to illustrate the relationship between the values of pseudo-reduced temperature T r,pseudo-reduced pressure p r, and compressibility factor Z for sweet natural gas. However,to make the chart applicable for simulation programming,a straight line was introduced to fit the Standing and Katz chart in a general form as5where A-D are correlation constants,Z is the com-pressibility factor,T r is the pseudo-reduced tempera-ture,and p r is the pseudo-reduced pressure.Gas Density.The density of natural gas F g can be calculated aswhere M g is the molecular weight,p is the pressure,R is the gas constant,Z is the gas compressibility factor, and T is the temperature of the system.Viscosity.Two types of viscosity can be used to characterize natural gas behavior:dynamic and kine-matic.The dynamic viscosity,a measure of a fluid’s resistance to flow,is defined as the ratio of the shear force per unit area to the local velocity gradient;this is represented by whereµis the dynamic viscosity,F is the flow rate,A is a unit area,v is the velocity gradient,and L is the length of the pipe.If temperature is involved,the equation for dynamic viscosity can be expressed as8whereµis the dynamic viscosity,M is the molecular weight,F g is the gas density,and T is the temperature of the system.Kinematic viscosity is the ratio of the dynamic viscos-ity of a fluid to its density,i.e.where v is the viscosity,µis the dynamic viscosity,andF is the gas density.2.4.Background on Gas Flow in Pipelines.The mathematical models used to design a natural gas transmission pipeline network system are based on algorithms derived from the principles of thermody-namics and fluid flow.They affect the characteristics of the natural gas flow that include system mass balance,system energy balance,and friction factor. System Mass Balance.The mass flow rate through the control volume does not vary with time.Therefore, the mass flow rate into the control volume must be equivalent to the mass flow rate out.This can be expressed aswhere d m cv is the system mass balance;m cv is the mass flow rate in a control volume;and m in and m out are the mass flow rates entering and leaving the control volume, respectively.System Energy Balance.Weymouth developed a general equation for calculating the steady-state iso-thermal flow of a gas through a horizontal pipe,based on the concept of energy conservationwhere q sc is gas flow rate measured at standard condi-tions in thousands of standard cubic feet per day (Mscfd),p sc is the pressure at standard conditions in pounds per square inch absolute(psia),T sc is the temperature at standard conditions in Rankine,p1is the upstream pressure in psia,p2is the upstream pressure in psia,d is the diameter of the pipe in inches,γg is the gas gravity,T is the flow temperature in Rankine,Z av is the average gas compressibility factor, f is a friction factor,and L is the length of the pipe in feet.Reynolds Number and Friction Factor.The Rey-nolds number can be determined using the velocity, density,and viscosity of the fluid as well as the cross-sectional area of the pipe.6Equation14is used to calculate the Reynolds numberwhere N Re is the Reynolds number,q sc is the gas flowTable1.Physical Constants for Typical Natural Gas Constituentscomponent molecularweight(g/mol)criticalpressure(psia)criticaltemperature(°R)CH416.043667.8343.1C2H630.070707.8549.8 C3H844.097616.3665.7 n-C4H1058.124550.7765.4 i-C4H1058.124529.1734.7 n-C5H1272.151488.6845.4 i-C5H1272.151490.4828.8 n-C6H1486.178436.9913.4 n-C7H16100.205396.8972.5 n-C8H18114.232360.61023.9 n-C9H20128.259332.01070.4 n-C10H22142.286304.01111.8 N228.013493.0227.3 CO244.0101070.9547.6 H2S34.0761306.0672.4 O231.999737.1278.6 H2 2.016188.259.9 H2O18.0153203.61165.1µ)10-4(9.4+0.02M)T1.5209+19M+Texp[(3.5+986T+0.01M)F g1.7+(197.2/T)+0.002M](10)v)µ/F(11)min)moutat d mcv)0(12)qsc)5.6353821(T sc p sc)[(p12-p22)d5γgZavTfL]0.5(13)NRe)20qscγg/(µd)(14)Tpc)∑y i T c i(5)ppc)∑y i p c i(6)Z)pr (ATr+B)+CTr+D(7)Fg)pMg/ZRT(8)µ)F/Ad v/d L(9)992Ind.Eng.Chem.Res.,Vol.43,No.4,2004rate in Mscfd,γg is the gas gravity,µis the dynamic viscosity in centipoise (cp),and d is the diameter of the pipe in inches.For gas flow in a smooth pipe,the friction factor depends mainly on the Reynolds number as followswhere f is a friction factor and N Re is the Reynolds number.Equation 15is applicable for the Reynolds numbers between 3000and 1000000.pressor Characteristics.According to the experience of operators who have long been operating compressors,the compressor capacity can be described as a function of the flow rate and the compression ratio in a graph as shown in Figure 1.Thus,the ratio of the discharge and suction pressures of a compressor can be expressed in the following formulaswhere R is the compression ratio and q is the flow rate in millions of standard cubic feet per day (MMscfd).When the compression ratio R has been defined and one of the values of either the discharge pressure,p discharge ,or the suction pressure,p suction ,is known,then the value can be computed with the following equation2.6Customers’Consumption Characteristics.Three major groups of natural gas consumers must be considered:industrial,dehydrator,and heat-sensitive.17Each group exhibits a different pattern of natural gas consumption expressed as a relationship between time and pressure,as shown in Figure 2.Natural gas is mainly utilized for heating purposes.Hence,the ambient temperature is the main determi-nant in the natural gas consumption of customers.14As a result,the natural gas demand is high in the winter and low in the summer.Figure 3shows a graph of natural gas demand during a typical year from January to December.If the consumption rate of each type of customer within one year is available,the total consumption rate of all customers in each season can be derived from the expressionwhere TotalConsmp is the total consumption rate,%MC is the percentage of consumption compared to the maximum load according to seasons,D is the yearly consumption of residential customers,C is the yearly consumption of commercial customers,F is the yearly consumption of farming customers,I is the yearly consumption of industrial customers,%IC is the per-centage consumption of industrial customers according to seasons,and days is the number of days of consump-tion in the year.2.7.Schematic of Natural Gas Pipeline Network System.The basic features in a natural gas pipeline network include pipes connected to form a pipeline network and natural gas flowing in at one end and out at the other end.A pipeline network generally consists of compressor stations and customer areas.For long-distance delivery,compressor stations need to be located between the primary compressor stations and customer areas to the maintain pressure of the natural gas throughout the pipeline network.Pipelines that branch out from the main lines transmit natural gas to several customer areas,as illustrated in Figure 4.The fundamental components of the natural gas transmission pipeline consist of nodes and node-connecting elements.Nodes are the points where a pipe leg ends,where two or more node-connecting elements are joined,or where there is an injection or delivery of natural gas.Node-connecting elements include pipe legs,compressor stations,valves,and pressure and flow regulators.Figure 4illustrates a loopless pipeline network system for natural gas transmission.A loopless pipeline network system contains nodes joined by one or more node-connecting elements with no closed loops.Such a system usually begins at the compressor station at node 1and transmits natural gas from node 1to node j ,for j )2,3,...,n +1.Between node 1and node 2,there is a pipe leg 1.Therefore,for n +1nodes intotal,Figure 1.Relationship between compressor capacity per unit flow rate and compression ratio.f )0.0056+0.5N Re-0.32(15)R )(0.4/18)[(BHP/q )+44.5]at 5<(BHP/q )<23(16)R )(0.4/12)[(BHP/q )+22.0]at 23<(BHP/q )<35(17)R )(0.1/2)[(BHP/q )+3.0]at 35<(BHP/q )<37(18)R )p discharge /p suction(19)Figure 2.Patterns of natural gasconsumption.Figure 3.General curve of natural gas demand in a year.TotalConsmp )[%MC ×(D /days +C /days +F /days)]+[(I /days)×%IC](20)Ind.Eng.Chem.Res.,Vol.43,No.4,2004993there are n pipe legs.At each node between node 1and node n +1,natural gas is delivered to each customer area.Mass balance and energy balance equations can be used to calculate the pressure and flow rate at each node.If one value among the node pressure,inlet pressure,or outlet pressure is given,the others can be calculated by a given set of pipe leg parameters and the flow rate into or out of the nodes.To determine the pressure at any node,eq 13can be generalized aswhere i )1,2,3,...,n ;j )2,3,...,n ,n +1;and p i is thepressure,q i is the flow rate;and k i is the correlation variable at node i .Meanwhile,the flow rate at a node can be computed using the mass balance equation applied from eq 12.By applying the mass balance equation with an analogy of Kirchhoff’s law for the flow of electricity in electrical networks,the sum of natural gas flows entering and leaving the pipeline system at any node is zerowhere m is the number of node-connecting elements andq i is the flow rate of natural gas at each node i .q i assumes a positive value for flow into node i and a negative value for flow out of node i.3.Conceptual Framework of a Computer-Aided Simulation Model for Natural Gas Pipeline Network SystemsThe components of the natural gas pipeline network and the relationships and properties of these compo-nents form the basis of the simulation model.The correspondence between the components of the pipeline system and the simulation model is shown in Table 2.To simulate a natural gas pipeline network system,the components throughout the system must be clari-fied.From Table 2,the main components,which to-gether make up the system state,consist of the sche-matic of the system,the number of stations,the number of compressors at each station,the customers,the pipes,and the natural gas components.The entities in the simulation model are the compressors,the customers,the pipes,and the natural pressors have their own attributes,such as break horsepower (BHP)and compression ratio.Customers are the entities that determine the natural gas consumption rate of the system.Pipes have attributes of diameter and length.The attributes of the natural gas are the percentages of hydrocarbon and non-hydrocarbon components in the natural gas.The pressure and flow rate at each cus-tomer location,which are the state variables,must be considered.These state variables can be changed by events during operation.The events can be (i)the actions of the dispatcher,such as turning a compressor on or off,or (ii)the change in the entities of the system itself,such as the consumption natural gas.In the actual operating system,the dispatcher moni-tors the state of the natural gas pipeline system from a computer screen.The pressure and flow rate are dis-played and updated within a time interval.The discrete-event simulation approach is applied to build the natural gas pipeline network system because the changes of state variables occur within a time interval.Moreover,the simulation model can dynamically provide the state variables as effectively as a real-time monitoring system does.Figure 5illustrates how the simulation model processes inputs and generates outputs.The simulation model is initialized when the user first inputs the parameters into the simulation model through the user interfaces.The input parameters include a schematic of the system,the number of stations,the number of compressors and the capacity of each com-pressor,number of customers and yearly consumption rate of each type of customer,the diameter and length of the pipes,the percentages of hydrocarbons and non-hydrocarbons componenets in the natural gas,and the range of pressure in the ing these inputs,the simulation model starts to simulate all variables in the natural gas pipeline network system and provide outputs through the user interface.The main user interface illustrates the outputs on the selected sche-matic according to the number of stations,compressors,and customers,as specified by the user.The naturalgasFigure 4.Schematic for the natural gas pipeline network system.p j 2)p 12-∑i )1j -1k i q i 2(21)∑i )1mq i )0(22)Table 2.Correspondence between the Components of the Natural Gas Pipeline Network System and the Items in the Simulation Model simulation model natural gas pipeline network systemsystem stateschematic of the system number of stationsnumber of compressors at each stationnumber of customer areas in the entire network number of pipes in the entire network natural gas componentsentities compressors,customers,pipes,natural gas attributes BHP,compression ratio,consumption rate,pipe diameter,pipe lengthpercentage of each hydrocarbon and non-hydrocarbon component in natural gasstate variables status of compressors (on,off),pressure,flow rateevents turning compressors on/off or up/down,changing consumption rateactivities deliver natural gas994Ind.Eng.Chem.Res.,Vol.43,No.4,2004properties and the state variables,pressure and flow rate,are simulated using all the equations discussed in section 2and displayed on the screen.The natural gas properties,molecular weight,specific gravity,com-pressibility factor,density,and viscosity,can be deter-mined using eqs 1-11.Equations 14and 15are applied to calculate the Reynolds number and friction factor,respectively.According to the season selected by the user,eq 20is used to simulate the consumption rate of customers and represent the flow rate of the pipeline system.To calculate the pressures at the nodes in the pipeline,the energy and mass balance relationships,eqs 21and 22,are applied in the simulation model.The system also generates recommendations on operation control to the dispatchers.Moreover,because of the possible changes in the consumption rates of the cus-tomers,the simulation model is designed to dynamically simulate the consumption rate every 15s.The simula-tion model also allows the dispatcher to decide whether to turn on/off or increase/decrease the capacity of the compressors during operation.When a change in the compressor status occurs,the compression ratio is shifted to a new level,which is calculated using eqs 16-18.Once the consumption rate or actions on compressors are changed,the state variables are automatically updated and displayed on the user interface.4.Case Study of a Natural Gas Pipeline Network System4.1.Background on the Case Study System.The natural gas pipeline network system used as a case study here is located in the St.Louis East area inSaskatchewan,Canada.The system consists of two compressor stations at St.Louis and Melfort.The system spans the region from the St.Louis station to the Melfort station and ends at the Nipawin and Hudson Bay customer areas.Natural gas is transmitted to 32customer areas.Some areas consist of all four types of customers,including domestic,commercial,farming,and industrial.Others have only two or three types of customers.Although there are many customer areas,the dispatcher usually focuses on only the pres-sure at the end points of the pipeline system.The reason for this approach is that,if the pressure at the end points is adequately maintained,the entire pipeline system will have enough pressure.Therefore,the places where the pressure should be gauged are the remote customer areas farthest from the St.Louis and Melfort stations.The most remote customer areas from the St.Louis station before reaching the Melfort station are Melfort and St.Brieux.The most distant areas from the Melfort station are Nipawin and Hudson Bay,located at the end of the pipeline system.Figure 6showsaFigure 5.Diagram of the processes in the simulation model for natural gas pipeline networksystems.Figure 6.Schematic of the St.Louis East system.Ind.Eng.Chem.Res.,Vol.43,No.4,2004995。
计算机网络参考文献
1《计算机网络》（第4版）英文影印版Andrew S. Tanenbaum 著清华大学出版社COMPUTER NETWORKSFOURTH EDfTlON简介：本书是国内外使用最为广泛的计算机网络经典教材。
全书按照网络协议模型（物理层、数据链路层、介质访问控制子层、网络层、传输层和应用层），自下而上系统地介绍了计算机网络的基本原理，并给出了大量实例。
在讲述各网络层的同时，还融合进了近年来迅速发展起来的各种网络技术，如In ternet 、SONET ADSL CDMA WLAN和蓝牙等。
另外，针对当前计算机网络的发展现状以及计算机安全的重要性，本书用了一整间的篇幅对计算机安全进行了深入讨论。
本书的适用对象很广泛。
对于学习计算机网络课程的本科生以及研究生，本书都可以作为教材或教学参考书，每一章后面的大量练习题，可用于课程作业或者复习要点。
对于从事网络研究、网络工程以及使用和管理网络的科研和工程技术人员，本书也是一本很有价值的参考读物。
2、《计算机网络》（第4版）Andrew S. Tanenbaum 著，潘爱民译清华大学出版社计算机网络（win）简介：本书是国内外使用最广泛的计算机网络经典教材。
本书为翻译版。
全书按照网络协议模型（物理层、数据链路层、介质访问控制层、网络层、传输层和应用层），自下而上系统地介绍了计算机网络的基本原理，并给出了大量实例。
在讲述各网络层的同时，还融合了近年来迅速发展起来的各种网络技术，如In ternet 、SONET ADSL CDMA WLAF和蓝牙等。
另外，针对当前计算机网络的发展现状以及计算机安全的重要性，本书用一整章的篇幅对计算机安全进行了深入讨论。
本书的适用对象很广泛。
对于学习计算机网络课程的本科生以及研究生，本书都可以作为教材或教学参考书。
每一章后面的大量练习题，可用于课程作业或复习要点。
对于从事网络研究、网络工程以及使用和管理网络的科研和工程技术人员，本书也是一本很有价值的参考读物3、《计算机网络》（第5版）谢希仁编著电子工业出版社L 询宦jE - 一' ■■丁° ' kun简介：本书自1989年首次出版以来，于1994年、1999年和2003年分别出了修订版。
计算机网络英语论文
Security of Computer Network System First, First, the the the importance importance importance of of of the the the network network network security. security. security. With With With the the the informationization informationization d evel eveloping fast today, the computer network obtained the wid oping fast today, the computer network obtained the widespread application, but but along along along with with with the the the network network network information information information transmission transmission transmission capacity capacity capacity growing growing growing faster, faster, some organizations and and d d epartments bene it the speedup with the the service service operation operation in in in the the the network, network, network, whil whil while, e, e, the the the data data data has has has also also also suffered suffered suffered to to to extent extent extent attack attack attack and and d estruction. estruction. The The aggressor aggressor may may may intercept intercept intercept the the information information in in the network, network, steals steals the user ’s password, the database information; also may tamper with the database content, the forge user’s status, d enies own signature. Second, network security rational rationale. e. International Standardization Organization (ISO) once suggested the computer security the d e inition was: “The computer system must protect its hardware, the data not accid entally or reveals intentionally, the change and the d estruction.” In ord e r to help the computer user er to help the computer user discrimination and the solution computer network security probl problem, em, the A merican merican Department Department Department of of of Defense Defense Defense announced announced announced “the “the “the orange orange orange peel peel peel book” book” book” (orange (orange book, book, of icial of icial of icial name name name is is “credibl “credible e computer computer system system system standard standard standard appraisal appraisal appraisal criterion”), criterion”), has has carried carried carried on on on the the the stipulation stipulation stipulation to to to the the the multiuser multiuser multiuser computer computer computer system system system security security security rank rank division. Third, Third, the the the network network network security security security should should should have have have function. function. function. In In In ord ord order er er to to to adapt adapt adapt the the information technol technology ogy ogy d d evelopment well, well, the the the computer computer computer network network application system must have foll owing function:（1）Access control.（2）Inspects the security l oophol oophole.e.（3）Attack monitoring.（4）Encryption communication.（5）Authentication.（6）Backup Backup and and and restoration.restoration.（7）Multi-layered Multi-layered d d efense.（8）Sets Sets up up up the the the safe safe monitoring center. Fourth, Fourth, the the the network network network system system system safety safety safety comprehensive comprehensive comprehensive solution solution solution measures. measures. If want to realize the network security function, we shoul should d carry on the Omni-directional Omni-directional guarding guarding guarding to to the network network system, system, system, and and thus formulate formulate the the quite reasonabl reasonable network security architecture. Below on the network system security e network security architecture. Below on the network system security problem, proposes some guard measure. 。
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计算机网络英文文献
电路交换网与vb调用数据库切换电路的连接设置的结果是保留了从发送端到接收端的包所通过的线路带宽。
其它的特性这一就是所有的包都沿同一个线路意味着如果包传输超过了时序那它将不能到达接收端.由于没有路径用来进行包交换，所以要想不同的包沿不同的本文源自六维论文网路径传送就是能依靠网络的条件了。
这样包即便是超过了时序它们也有可能到达的。
包交换技术比线路交换技术更能容错。
事实上，这也是它被发明的理由！当一个交换开头被拉下，则所有使用它的线路将被切断并且其余的包将不能再被传送。
此时如果在进行包交换，包将在已选择的路径上停止交换。
预先建立一条路径也开创预先保留带宽的可能性。
如果带宽被保留，那么当一个包到达时，通过保留的带宽它可以被立即发送出去。
假如没有带宽被保留用于包交换，那么所有的包将不得不等待着被转发。
预先保留带宽意味败。
因此，在线路交换(在设置时)和包交换(在包发送时)的不同时间拥塞都可能发生。
如果为特定的用户建立一条线路那么当这个用户没有数据传送时，则这些保留下来的带宽将被浪费而不能用于其它用户的传输。
而包交换则不会浪费带宽，因此它在系统宽带方面的应用更有前景。
理解电路交换和包交换的这种商业差别是极其重要的。
这种商业差别是在质保服务和浪费资源相对不质保服务和不浪费资源的。
包交换是利用存储器并向前发送的。
包是先存储在路由器的内存里然后再发送到下一个路由器的。
和电路交换一样信息位也是连续不断地通过导线传输的。
存储转发技术增加了延迟时间。
另一个不同是电路交换是完全透明的。
发送者和接收者可以使用他们想要的任一比特速率，格式和帧同步.这通信公司不知道也不关心这的。
而在包交换中载体决定了基本的参数的。
用一个简单比喻它们就像一个是公路一个是铁路。
在以前，用户决定介质的大小，速度和特性。
而后来这些都由通信公司做了的。
这些都是透明的它允许声音，数据和传真共同存在于电话系统里。
电路交换和包交换的最后一个不同点是计费方式。
电路交换的计费是按照传统的距离和时间的。
比如移动电话除打国际电话外距离是不列入计算的，而时间也只是列入一个简单的计算(例:拔打2000分钟电话比1000分钟电话花费的多并且晚上或周末也比平时来得便宜)。
时间对于包交换来说是没有问题的，但是传输流量却是个问题。
ISPs为家庭用户的计费方式基于按一个月的流量的一半的，这是因为它们用得相对较少并且他们的顾客也很好理解这种计费方式。
但是主干网络中心的收费是基于它们的流量的。
这些不同列在图2-40里。
项目电路交换包交换
呼叫设置需要不需要
专用物理线路是否
每个包沿相同路径是否
包的到达中有规则的是否
是否会致命的崩溃是否
带宽利用固定动态分配
可能的时间堵塞在设置时在每个包时
可能浪费带宽是否
以存储转发进行发送否是
透明性是否
收费按分钟按包
图2－40：比较电路交换网络和包交换网络的不同
电路交换和包交换是两者都是非常重要的，我们将立即在详细的资料里提及并描述它们之间各种不同的技术。
2.6 移动电话系统
传统的电话的系统将不能满足用户的大量增长（即有一天实现了终端到终端的光纤连接）。
人类在进步。
因此有很多的人关心无线电话技术。
在下面的章节我们将用详细的资料来学习这些主题。
无线电话可以分为基本的两种：无绳电话和移动电话（有时也叫蜂窝电话）。
无绳电话设备是由痤机和听筒组成它们被安装在用户的家里。
它们从不被应用于网络，所以我们没有办法做进一步的检测。
取而代之，我们将把焦点放在在声音和数据通信上有广泛应用的移动系统上。
移动电话经历了三个不同的发展阶段，每个阶段都有不同的技术：
1．模拟声音
2．数字声音
3．数字声音和数据（互联网，电子邮件，etc.）
虽然我们主要讨论这系统技术，但是我们也有必要注意政府和市场对它的巨大影响。
第一个移动电话系统是在美国由受美国国家联邦通讯委员会(FCC)委托的美国电话电报公司(AT&T)设计的。
结果在整个美国就有了一个简单的(模拟)系统并且移动电话开始在加利福尼亚上市同时也在纽约得到应用。
相反的，当移动电话来到欧洲时，由于每个国家都设计了自己的系统，所以结局很惨败。
当数字技术到来时，欧洲从前面的失败中吸收教训，政府和邮政制定了简单系统(GSM)的统一标准，因此移动电话在欧洲的任何一个地方都是通用的。
此时，美国政府决定不把标准商业化因而它失去了数字市场。
这个决定导致不同的设备生产商生产出不同的移动电话。
结果现在美国有两不可兼容的数字移动电话在使用(加强了一家就会削弱另一家)。
即使美国拥有移动电话的所有权，但是在应用上欧洲要远远超过美国的。
原因之一就是整个欧洲拥有相同的简单系统。
然而更多的是由于美国和欧洲的基本电话数量不同。
在美国移动电话和固定电话是共用的，因此对于用户没有办法区分(212)234-5678到底是固定电话(拨打是便宜的或者是免费的)还是移动电话(拨打是昂贵的)。
为了使人们从使用电话中获益，电话公司决定为引入呼叫而花自己的钱制造移动电话。
结果导致，很多人怕由于呼叫而收到一大笔帐单而不愿意买移动电话。
在欧洲移动电话有特殊的区号(如800,900之类的数字)，所以它很快就得到了认可。
因而在一般的“叫方付费”的原则在欧洲也被应用于移动电话了(除国际电话分开收费外)。
在欧洲采用颁布广泛的已经付费的移动电话的影响巨大(超过同地区的75%)。
移动电话可以在很多的商店里购买而不像购买收音机那样需要很多手续。
谁付费谁使用，他们预先存入，比如20或50 euro并且在快用完的时候可以用PIN码进1355。