计算机网络中英文翻译
计算机网络
来自维基百科
网址：https://www.360docs.net/doc/d32805241.html,/wiki/Computer_network
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。网络可以根据其多种特点来分类。计算机网络允许资源和信息在互联设备中共享。
目录
1．历史
2．目的
3．网络分类
3.1 连接方式
3.2 有线技术
3.3 无线技术
3.4 规模
3.5 功能关系(网络体系结构)
3.6 网络拓扑结构
4. 基于物理范围的各种类型的网络
4.1 局域网
4.1.1 个人区域网
4.1.2 家中大面积网络
4.2 广阔的地区网络
4.2.1 校园网络
4.3 大都会区域网
4.3.1 企业专用的网络
4.3.2 虚拟专用网络
4.3.3 网际网络
4.4 骨干网
4.4.1 全球区域网
4.4.2 互联网
4．4.3 内部网和外部网
4.4.4 覆盖网络
5．参考文献
一．历史
早期的计算机网络通信始于20世纪50年代末，包括军事雷达系统、半自动地面防空系统及其相关的商业航空订票系统、半自动商业研究环境。
1957年俄罗斯向太空发射人造卫星。十八个月后，美国开始设立高级研究计划局(ARPA)并第一次发射人造卫星。然后用阿帕网上的另外一台计算机分享了这个信息。这一切的负责者是美国博士莱德里尔克。阿帕网于来于自印度，1969年印度将其名字改为因特网。上世纪60年代，高级研究计划局(ARPA)开始为美国国防部资助并设计高级研究计划局网(阿帕网)。因特网的发展始于1969年，20世纪60年代起开始在此基础上设计开发，由此，阿帕网演变成现代互联网。二．目的
计算机网络可以被用于各种用途:
为通信提供便利:使用网络，人们很容易通过电子邮件、即时信息、聊天室、
电话、视频电话和视频会议来进行沟通和交流。
共享硬件:在网络环境下，每台计算机可以获取和使用网络硬件资源，例如打印一份文件可以通过网络打印机。
共享文件：数据和信息: 在网络环境中，授权用户可以访问存储在其他计算机上的网络数据和信息。提供进入数据和信息共享存储设备的能力是许多网络的一个重要特征。
共享软件:用户可以连接到远程计算机的网络应用程序。
信息保存。
安全保证。
三．网络分类
下面的列表显示用于网络分类：
3．1连接方式
计算机网络可以据硬件和软件技术分为用来连接个人设备的网络，如：光纤、局域网、无线局域网、家用网络设备、电缆通讯和G.hn（有线家庭网络标准）等等。
以太网的定义，它是由IEEE 802标准，并利用各种媒介，使设备之间进行通信的网络。经常部署的设备包括网络集线器、交换机、网桥、路由器。无线局域网技术是使用无线设备进行连接的。这些设备使用无线电波或红外信号作为一种传输媒介。ITU-T（电信标准部门）的G.hn技术使用现有的家庭布线（同轴电缆，电话线和电源线）创建一个高速（可达1Gb/S）局域网。
3.2有线技术
双绞线是目前应用最广泛的通讯媒介。它由铜线扭曲配对而成。普通电话线
由两个绝缘铜导线配对扭成。计算机网络布线由四对铜电缆构成，可以进行语音结构和数据传输。使用双绞线电缆可以减少交调失真，电磁感应。它的传输速度的范围很广，从200万b/s至1亿b/s。双绞线电缆有两种类型非屏蔽双绞线(UTP)和屏蔽双绞线(STP)，它们被用在不同的场合。
同轴电缆广泛用于有线电视系统、写字楼、和其他工作区域的局域网。该电缆通常由铜或铝合金丝用带有高介电常数的灵活性材料绝的缘层包裹，所有这一切都被导电层环绕。绝缘层帮助减少干扰和变形。传播速度的范围从2亿b/s到超过5亿多b/ s。
光纤，是由一个或多个细丝状的玻璃纤维包裹在保护层中。光纤不受电磁辐射。它透过光线延续的传播速度可以达到上万亿b/s。光纤的传输速度比同轴电缆的传输速度快几百倍，比双绞线的速度快上千倍。
3.3无线技术
地面微波——使用地面上的微波发射器和接收器。设备看起来像卫星接受器。地面微波使用的是频率在千兆赫范围以内的波，这限制了所有通信线路出现在我们的视线中。中继站之间的距离大约为30英里。微波天线通常放在建筑物的顶上，例如：塔、丘陵或者山峰的峰顶。
通信卫星——卫星广播使用微波通信，而微波传输不会因地球大气层而产生偏转。卫星安置在太空中，一般在赤道上22000英里(对于同步卫星来说)的高空。这些绕地卫星系统能接收和转播语音、数据、电视信号。
蜂窝技术和个人通信服务系统，使用几种无线电通讯技术。这类系统被分布到不同的地理区域。每个区域都有低功率发射器或无线电中继天线装置来把电话通信从一个地区传递到下一个地区。
无线LAN,即无线局域网使用高频无线电技术，类似数字蜂窝和低频无线电技术。无线局域网使用扩频技术来实现有限区域内多个设备之间的通信。一个开放式标准的无线电波技术的例子就是IEEE。
红外通信，它能在设备之间进行短距离的不超过10米的点对点(面对面)的信号传输，传输线路之间不能有障碍。
3.4规模
网络通常分为局域网(LAN)、广域网(WAN)、城域网(MAN)、个人区域网络(PAN)、虚拟专用网(VPN)、校园局域网(CAN)、存储区域网络(SAN)。而其它一些国家，则根据其规模、范围和目的分类。例如，控制器局域网(CAN)的使用，信任水平和进入权利之间同这些类型的网络大有不同。局域网往往是专为内部使用的一种组织内部系统和员工个人物理位置的网络，比如建筑，而广域网路可以连接物理上独立的部分，而且可能包括连接一个组织给第三方。
3.5功能关系(网络体系结构)
计算机网络的功能关系可以根据元素中存在的网络进行分类。如，主动网络、客户端—服务器、无线自组网络和点对点(工作组)建筑。
3.6网络拓扑结构
计算机网络分类是根据网络拓扑结构建立的，如总线网络，星型网络，环网，网格。网络拓扑的协调基于他们在网络设备上逻辑关系的排列，彼此独立于物理的安排。即使网络计算机放置在一个线性安排和被连接到一个集线器，网络仍是星型拓朴结构，而不是总线网的结构。一个网络在这方面的视觉和操作特性是不同的。网络可以基于数据分类的方法以用于传递数据，包括数字和模拟网络。4.基于物理范围的各种类型的网络
常见的可以确定其规模的计算机网络类型。
4.1局域网
局域网(LAN)是一个连接在有限地区的电脑网络或设备。如家庭、学校、计算机实验室、办公楼、或接近的建筑物。每台计算机或设备，对网络是一个节点。新的标准ITU-T G.hn也提供一种方法即使用现有的家庭电线（同轴电缆，电话线和电源线）来创建一个有线局域网。
典型的图书馆网络，在一个分支树拓扑结构和控制对资源的访问
所有相互关联的设备必须了解网络层(第三层)，因为他们要处理多个子网(不同的颜色)的。图书馆里面只有10/100 Mbit / s的以太网连接到用户设备和千兆以太网连接到中央路由器，可以称为―第3层交换机‖，因为他们只有从以太网接口才能了解IP。这将是更正确的称呼他们的接入路由器，在顶部的路由器是一个通讯路由器，它是学生连接到互联网和学院网络的接入路由器。
局域网的界定特征，和广域网络(广域网的关系)相比较而言，局域网有更高的数据转移率、小地理范围,并且不需要租赁电信线路。当前的局域网或其他电气与电子工程协会802.3局域网技术操作的速度达10 千兆比特/秒。这是数据传输速率。IEEE已经计划审查的标准是40到100 千兆比特/秒。
4.1.1个人区域网
个人区域网络(盘)是用于一个人周围的计算机和使用不同信息技术的设备之间进行交流的网络。在个人区域网中使用的设备有个人电脑、打印机、传真机、电话、PDA、扫描仪甚至是视频游戏机。一个个人区域网可能包括有线和无线设备。个人区域网的范围通常延伸到10米。个人有线区域网通常采用USB数据线及高速的序列文件连接来构建,而蓝牙通信技术与红外通信技术则形成了典型的个人无线区域网。
4.1.2家庭区域网络
一个家庭区域网络(HAN)是一个住宅局域网，一般可用于部署在家里的数字设备之间的通信，如少量的个人电脑及配件，打印机和移动计算设备。它的一种重要功能是是通过有线电视或数字用户线（DSL）提供的宽带服务来共享上网，它也可以被称为一个办公区域网络(OAN)。
4.2广域网
广域网(WAN)是覆盖了一个城市，国家一个很大地理区域的计算机网络,如城市、国家或跨洲际距离,使用的通信信道是有多种媒体如电话线、电缆和无线电波相结合的信道。广域网使用的传输设备通常是有公共电信运营商提供的，如电话公司。广域网技术的一般功能体现在开放式系统互连（OSI）参考模型较低的三层:物理层,数据链路层和网络层。
4.2.1校园网
校园网是一个在有限的地理区域连接成的局域网(LAN)计算机网络。网络设备(交换机、路由器)和传输媒体(光纤、铜厂、Cat5布线等)是几乎完全属于(校园承租人/所有者的:企业、学校、政府等)。
就大学校园的校园网络建设来说，网络是将各种各样的校园建筑，如，学术
部门，大学图书馆和学生学员公寓等连在一起的。
4.3城域网
一个大城市的网络是一个大型计算机网络，通常跨越城市或一个大的校园
EPN帧中继广域网的连接和远程拨号访问。
VPN用来连接3个办公室和远程用户
4.3.1企业专用网
企业网是由企业建设用来互联公司各个部门的网络，如生产基地、总部、远程办公室、商店等为了共享电脑资源而设立的。
4.3.2虚拟专用网
虚拟专用网络（VPN）是一种特殊的计算机网络，其中某些节点之间的联系通过公开式电路连接或通过一些较大的网络（例如，互联网）中的虚拟链路，而
不是通过物理线路。这种通过大型网络的虚拟专用网使用的数据链路层协议被称为隧道。安全通信是公用因特网中一个常见的应用，但VPN不需要这种明确的安全性能，如认证或者内容加密。例如，VPN可以被用来分离不同用户在拥有强大安全特性的底层网络进行通讯时的流量。
VPN可能有尽力而为的特性或在VPN客户端和VPN服务提供者之间有固定的服务等级协定(SLA)。一般来说，VPN拓扑比点对点要复杂的多。
4.3.3互联网络
一个网际网路使用路由器通过一种常见的路由技术(OSI第三层) 连接两个或更多的私人计算机。互联网是许多互联网络的一个集合，因此被缩短称为互联网。
4.4骨干网
骨干网络(BBN)，骨干网络或网络骨干是计算机网络基础设施的一部分，它连接了不同种类的网络，并且它提供了不同局域网和不同子网之间进行通信的路径。骨干网可以将在同一座楼里、不同的建筑物中、校园环境中或国外的不同网络连接起来。通常，骨干网络的承载能力大于连接到它上面的网络。
在一家拥有分布在不同区域子公司的大公司里，可能有骨干网将不同的区域连接在一起，例如，如果一个服务器集群系统需要被公司内坐落于各种不同的地理位置的部门访问。将不同部门连接在一起的那部分网络(例如:局域网，无线网)经常被称作网络骨干。在骨干网络的设计中经常会考虑到网络拥塞的问题。不应将骨干网络和因特网骨干混同。
4.4.1全球区域网络
全球区域网络(GAN)是一个用于支持通过任意数量的无线局域网、卫星覆盖
区域等进行移动通信的网络。移动通信的主要挑战是处理从一个覆盖地区转到另一个地区的用户通信。电气与电子工程协会802项目涉及一系列地面无线局域网。
4.4.2互联网
互联网是一个全球性的联结政府、学术、公司、公共领域和私人计算机系统的网络。它基于互联网的网络技术协议组件。这继承了由美国国防部开发研制的高等研究计划署网络(阿帕网)。互联网也是万维网(WWW)的通信主干。
4.4.3内部网和外部网
内部网和外部网是一个计算机网络的延伸部分，它通常是一个局域网。
内部网是一系列网络的集合，它使用网际协议和基于网际协议的工具，如浏览器和文件传输应用程序，他们由单一管理实体进行管理。管理实体只对授权的用户开放内联网。通常内部网是一个机构的内部网络。一个大的内联网一般会有至少一个网络服务器，为用户提供组织过的信息。
外部网被限制在单一的组织或实体的范围内，通常它也会被限制连接到一个或多个组织或实体。但不一定是受信任的组织或实体，例如公司的客户可能获得企业内部网的访问权限，同时从安全的观点来讲客户可能不会被认为是可信赖的。从技术上讲，外部网也被分类为CAN、MAN、WAN或者其他类型的网络。尽管外联网不能只包括单一的一个局域网，它必须拥有至少一个与外部网络的连接。
4.4.4覆盖网络
覆盖网络是一个建立在另一个计算机上面网络上面的虚拟网络。覆盖网络中的每个节点通过虚拟的或者逻辑上的链接相连，每个节点都对应一条路径，或者
在底层网络通过许多物理链接来连接网络。
覆盖网络的样本: 在SONET光纤上的IP
Computer network
From Wikipedia, the free encyclopedia
"Computer networks" redirects here. For the periodical, see Computer Networks (journal).
A 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.
Contents
1 History
2 Purpose
3 Network classification
3.1 Connection method
3.2 Wired technologies
3.3 Wireless technologies
3.4 Scale
3.5 Functional relationship (network architecture)
3.6 Network topology
4 Types of networks based on physical scope
4.1 Local area network
4.1.1 Personal area network
4.1.2 Home area network
4.2 Wide area network
4.2.1 Campus network
4.3 Metropolitan area network
4.3.1 Enterprise private network
4.3.2 Virtual private network
4.3.3 Internetwork
4.4 Backbone network
4.4.1 Global area network
4.4.2 Internet
4.4.3 Intranets and extranets
4.4.4 Overlay network
5 References
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 His 1st Satellite Within 18 Month After Establishment.Then Sharing Of The Information In Another 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 the 1960s.[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 preservation.
Security.
Network classification
The following list presents categories used for classifying networks.
Connection method
Computer networks can be classified according to the hardware 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. Transmission speed 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 speed may 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 a twisted-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 relaying voice, 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 among the elements of the network, e.g., active networking, client–server, Wireless ad hoc network and peer-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 scope
Common 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 Ethernet technology, 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 that connects 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 US
B 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 networking equipments (switches, routers) and transmission media (optical fiber, copper plant, Cat5 cabling
etc.) 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 a large campus.
Sample EPN made of Frame relay WAN connections and dialup remote access.
Sample VPN used to interconnect 3 offices and remote users
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 the larger 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. Network congestion is often taken into consideration while designing backbones.
Backbone networks should not be confused with the Internet backbone.
Global area network
变速器论文中英文对照资料外文翻译文献
中英文对照外文翻译 汽车变速器设计 我们知道，汽车发动机在一定的转速下能够达到最好的状态，此时发出的功率比较大，燃油经济性也比较好。因此，我们希望发动机总是在最好的状态下工作。但是，汽车在使用的时候需要有不同的速度，这样就产生了矛盾。这个矛盾要通过变速器来解决。 汽车变速器的作用用一句话概括，就叫做变速变扭，即增速减扭或减速增扭。为什么减速可以增扭，而增速又要减扭呢？设发动机输出的功率不变，功率可以表示为 N = w T，其中w是转动的角速度，T 是扭距。当N固定的时候，w与T是成反比的。所以增速必减扭，减速必增扭。汽车变速器齿轮传动就根据变速变扭的原理，分成各个档位对应不同的传动比，以适应不同的运行状况。 一般的手动变速器内设置输入轴、中间轴和输出轴，又称三轴式，另外还有倒档轴。三轴式是变速器的主体结构，输入轴的转速也就是发动机的转速，输出轴转速则是中间轴与输出轴之间不同齿轮啮合所产生的转速。不同的齿轮啮合就有不同的传动比，也就有了不同的转速。例如郑州日产ZN6481W2G型SUV车手动变速器，它的传动比分别是：1档3.704:１；2档2.202:1；3档1.414:1；4档1:1；5档（超速档）0.802:1。 当汽车启动司机选择1档时，拨叉将1/2档同步器向后接合1档
齿轮并将它锁定输出轴上，动力经输入轴、中间轴和输出轴上的1档齿轮，1档齿轮带动输出轴，输出轴将动力传递到传动轴上（红色箭头）。典型1档变速齿轮传动比是3:1,也就是说输入轴转3圈，输出轴转1圈。 当汽车增速司机选择2档时，拨叉将1/2档同步器与1档分离后接合2档齿轮并锁定输出轴上，动力传递路线相似，所不同的是输出轴上的1档齿轮换成2档齿轮带动输出轴。典型2档变速齿轮传动比是2.2:1，输入轴转2.2圈，输出轴转1圈，比1档转速增加，扭矩降低。 当汽车加油增速司机选择3档时，拨叉使1/2档同步器回到空档位置，又使3/4档同步器移动直至将3档齿轮锁定在输出轴上，使动力可以从轴入轴—中间轴—输出轴上的3档变速齿轮，通过3档变速齿轮带动输出轴。典型3档传动比是1.7:1，输入轴转1.7圈，输出轴转1圈，是进一步的增速。 当汽车加油增速司机选择4档时，拨叉将3/4档同步器脱离3档齿轮直接与输入轴主动齿轮接合，动力直接从输入轴传递到输出轴，此时传动比1:1，即输出轴与输入轴转速一样。由于动力不经中间轴，又称直接档，该档传动比的传动效率最高。汽车多数运行时间都用直接档以达到最好的燃油经济性。 换档时要先进入空档，变速器处于空档时变速齿轮没有锁定在输出轴上，它们不能带动输出轴转动，没有动力输出。 一般汽车手动变速器传动比主要分上述1－4档，通常设计者首先确定最低（1档）与最高（4档）传动比后，中间各档传动比一
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1.前言 互联网满36岁，仍然是一个进展中的工作。36年后在加州大学洛杉矶分校的计算机科学家使用15英尺的灰色电缆连接两台笨重的电脑，测试了一种在网络上新的数据交换的方式，这将最终成为互联网依然是一个在取得进展的工作。 大学的研究人员正在试验如何提高网络容量和速度。编程人员正在设法为网页注入更多的智能。并正在进行重新设计网络以减少垃圾邮件（垃圾邮件）和安全麻烦的工作。 与此同时威胁织机：批评人士警告说，商业，法律和政治压力可能会阻碍一些使互联网发展到今天的创新的类型。 斯蒂芬克罗克和温顿瑟夫属于1969年9月2日研究生加入的加州大学洛杉矶分校斯莱昂兰罗克教授工程实验室的团体，作为位无意义的测试数据两台计算机之间默默流动。到第二年的1月，其他三个“节点”加入到了这个网络。 然后是电子邮箱，几年之后，在七十年代后期一个所谓的核心通信协议即TCP / IP 协议，在80年代域名系统和在1990年万维网-现在的第二个最流行的应用背后电子邮件出现了。互联网的扩大，超出其最初的军事和教育领域延伸到了企业和全球的家庭中。 今天，克罗克仍然为互联网工作，为协作设计更好的工具。作为互联网管理机构的安全委员会主席，他正试图保卫系统的核心处理免受来自外部的威胁。 他认识到，他帮助建立的互联网工作远未完成，而这些改变是在商店，以满足多媒体日益增长的需求。网络供应商现唯一的“最佳努力”是在提供的数据包上。克罗克说，需要有更好的保障，以防止跳过和过滤现在常见的视频。 瑟夫，现在在MCI公司说，他希望他建立了有内置安全的互联网。微软，雅虎和美国在线公司，和其他的一些，目前正在努力改进网络，使邮件发送者可以验证的方式发送以降低使用虚假地址发送垃圾邮件。 瑟夫说，现在正在制定许多功能，是不可能立即解决计算速度慢和互联网管道窄，或
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机械毕业设计英文外文翻译436手动变速器 (2)
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计算机网络体系结构外文翻译
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二轴式手动变速器外文翻译
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计算机网络外文翻译
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计算机网络中英文互译
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计算机网络10种硬件设备介绍
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损耗，在线路上传输的信号功率会逐渐衰减，衰减到一定程度时将造成信号失真，因此会导致接收错误。中继器就是为解决 这一问题而设计的，它完成物理线路的连接，对衰减的信号进行放大，保持与原数据相同。如上图所示，经过远距离传输过来的信号经过中继器处理后，再传输到各设备。 三、网桥 网桥（Bridge）像一个聪明的中继器。中继器从一个网络电缆里接收信号，放大它们，将其送入下一个电缆。相比较而言，网桥将两个相似的网络连接起来，并对网络数据的流通进行管理。它工作于数据链路层，不但能扩展网络的距离或范围，而且可提高网络的性能、可靠性和安全性。网桥可以是专
汽车变速器外文翻译
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变速器外文资料翻译
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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
New technique of the computer network Abstract The 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. keywords Internet Network System Digital Certificates Grid Storage 1. Foreword Internet turns 36, still a work in progress Thirty-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 the second 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.