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1、信息类专业英语 第二章第1页，本讲稿共90页13.1 论文标题的写作论文标题的写作科技论文必须有一个简明、确切的标题。标题必须简短精练,概括性强,一般应控制在12个单词以内。标题应该鲜明地概括论文的主题。为了简明,标题一般不是一个完整的句子,而只是一个词组,甚至不必强求语法上的严格性或完整性而进行适当省略。第2页，本讲稿共90页13.2 论文摘要的写作及常用句型论文摘要的写作及常用句型摘要是论文的一个重要组成部分,有利于读者概要地了解论文的主要内容,有利于编目检索。联合国教科文组织建议:“全世界公开发表的科技论文,不管由什么文字写成,都应附有一篇短小精悍的英文摘要。”由此可见撰写英文摘要的重要
2、性。论文摘要的质量好坏,直接影响论文本身的科学价值和对外学术交流的效果。摘要虽然一般放在正文的前面,但却应在整篇论文完成以后再进行写作,以便如实摘取论文的要点。论文摘要一般包括如下内容:(1)研究的目的与意义。(2)研究的方法与途径。(3)研究的成果与结论。第3页，本讲稿共90页总之,论文摘要应包括足够的信息,使读者渴望阅读论文的正文。摘要应该简明扼要,不必解释。摘要应该公正客观,不要令读者有强加之感。摘要应该突出特点,令读者感到有阅读正文的必要。在写作摘要时,应注意以下几点:(1)开门见山地点明论文的主题,即论文的目的与意义。(2)简短列举论文的主要工作成果。(3)强调论文的新思想与特点。(
3、4)一般采用第三人称和现在时态,以显示客观性。(5)多用被动语态,既显示客观性,又符合科技英语的习惯。第4页，本讲稿共90页13.3 论文摘要的常用句型论文摘要的常用句型(1)In this paper,.is(are)presented(described,discussed,investigated,studied).(2)This paper(article,thesis)focuses on(presents,describes,discusses).(3)The purpose(aim,objective,attempt)of this paper is to.(4)The appr
4、oach is based on.(5)Conditions are considered for.(6)The requirement for.(7)The simulation is performed by using.第5页，本讲稿共90页(8)This method is confirmed experimentally with.(9)The result of this study can be summarized for.(10)Results forare found to be close to the experimental data(11)This paper de
5、monstrates.(12)The analysis of this study illustrates.第6页，本讲稿共90页13.4 例例 子子(1)Title:A General Purpose VLSI Frequency Synthesis SystemAbstract:A design for a general purpose VLSI frequency synthesizer is presented.It is shown that a simple basic design can have a fully professional performance.Some o
6、f the special requirements placed on the VLSI technology are discussed.第7页，本讲稿共90页(2)Title:Extraction of Frequency Modulation Laws in Sound SynthesisAbstract:The general scope of this study is computer music,especially the digital synthesis of music sounds.The paper presents a method of estimating m
7、odulation laws,using the“skeleton”associated with the wavelet transform and its application to signals generated by the frequency modulation synthesis technique.第8页，本讲稿共90页(3)Title:Very Fast Discrete Fourier Transform Using Number Theoretic TransformAbstract:It is shown that number theoretic transfo
8、rm(NTT)can be used to compute discrete Fourier transform(DFT)very efficiently.By noting some simple properties of number theory and the DFT,the total number of real multiplications for a length-p DFT is reduced to(p-1).For a proper choice of transform length,the number of adds per point is approxima
9、tely the same as the number for FFT algorithms.第9页，本讲稿共90页Unit Two TelecommunicationsPassage A Evolution of Telecommunication Networks Passage B Telecommunications Passage C Telecommunications:a brief historical review 第10页，本讲稿共90页Passage A Evolution of Telecommunication NetworksThe first phase in t
10、he evolution of communication networks is dominated by the wide spread of telephony and covers over 90 years.However,the telegraph preceded the telephone by more than 30 years and the teletypewriter by half a century.In 1844,Samuel Morse,the telegraphs inventor,sent the first telegraph message from
11、Washington D.C.to his colleague Alfred Vail in Baltimore,Maryland.Shortly after the invention of the telephone by Alexander Grahan Bell in 1876,it was realized that telephone wires had to converge on central points where telephone-to-telephone connections could be made.1 These points were manual swi
12、tch-boards,staffed by operators.This was followed by the introduction of electromechanical switching and in 1889,Almond第11页，本讲稿共90页B.Strowger invented the first two-motion step-by-step switch.In a step-by-step switch,a call was established and routed in a set of progressive electromechanical steps,e
13、ach under the direct control of the users dialing pulses.It remained as the workhorse of central office switching well into the 1970s.The first crossbar switch was used in 1932 in Sweden.The Bell System introduced the No.1 Crossbar System in 1938.Crossbar switching was carried out by a special circu
14、it called a marker,which provided common control of number entry and line selection for all calls.2第12页，本讲稿共90页电信网的发展进程电信网的发展进程 在通信网的发展进程中，第一个阶段是由电话的发展支配了九十多年。然而，电报比电话早出现30年，比电传打字电报机早出现半个世纪。在1844年，电报的发明者塞缪尔莫尔斯从华盛顿向他在马里兰巴尔的摩的同事阿尔弗雷德韦尔首次发送了电报。在1876年亚历山大，格雷厄姆贝尔发明电话后不久，人们就认识到，电话线必须在进行电话与电话接续的中心点集中。这些中心点
15、即为人工交换台，并配备有话务员。随后又出现了机电式交换，并且在1889年，阿尔莫德B史端乔发明了第一个两级动作步进式接线器。在步进式接线器中，可以一系列的机电动作逐步进行而建立呼叫和路由选择，这每一步都是在用户拨号脉冲的直接控制下进行的。进入七十年代以后，它仍然是中央交换室的主要设备。第一个纵横制接线器于1932年在瑞典被使用。1938年，贝尔系统推出了1号纵横制系统。纵横制交换由一个称为标志器的特定电路控制，标志器提供进入号码的公共控制并选择所有呼叫的路由。第13页，本讲稿共90页The golden age of automatic telephony occurred after Wor
16、ld Warwhen the entire long-distance network was automated.The invention of the transistor spurred the application of electronics to switching systems and led to the deployment of the first electronic switching in the late 1950s.Electronic switching made it possible to design and build switches with
17、greater capacity.第14页，本讲稿共90页自动电话的黄金时代出现在第二次世界大战之后，当整个长途网络实现自动化时。晶体管的发明促进了电子技术在交换系统中的应用，并导致了在五十年代后期首次采用电子交换制。电子交换使设计和构造更大容量的接线器成为可能。第15页，本讲稿共90页In the mid 1930s,analog point-to-point radio-relay transmission was possible by extending high-frequency(HF)communication technology into the very-high-freq
18、uency(VHF)range.During World War,the operating frequency bands of the analog radio-relay systems were extended into the ultra-high-frequency(UHF)range.The first link with over 100 repeater stations was placed into commercial service in 1951 between New York and San Francisco,operating in the 4 GHz b
19、and with a 20 MHz band.This was followed by a growth of medium and high-capacity analog radio-relay systems worldwide.By the early 1970s,digital microwave radio had gained importance and,by the 1980s,quadrature amplitude modulation(QAM)methods were widely used as the modulation scheme for digital ra
20、dio-relay systems.第16页，本讲稿共90页三十年代中期，由于高频（HF）通信技术延伸到甚高频（VHF）范围，使点到点无线电模拟中继传输成为可能。在第二次世界大战期间，无线电模拟中继系统的工作频带又扩展到超高频（UHF）范围。具有100多个中继站的第一条链路于1951年在纽约至旧金山之间投入商用，工作频带为4GHz，带宽20MHz。随后，中、大容量模拟中继在世界范围得到发展。七十年代初期，无线电数字微波获得重要位置，到八十年代，正交调幅方式被广泛用作无线电数字中继系统的调制方式。第17页，本讲稿共90页The second phase of networking,which o
21、ccurred in the 1960s,included three major milestones:software switching,digital transmission,and satellite deployment.In 1965,American Telephone and Telegraph(AT&T)introduced the first stored-program control(SPC)local switch,the 1 EES switching system.With the use of software control,a family of cus
22、tom calling services(speed calling,call waiting,call forwarding and three-way calling,etc.)was made possible.The first software program for the 1 ESS switching system had approximately 100,000 lines of code;today switches may contain ten million lines of code.第18页，本讲稿共90页网络的第二个阶段出现在六十年代，它包括三个主要的里程碑：
23、软件交换、数字传输和卫星的应用。1965年，美国电报电话公司（AT&T）推出了第一台存贮程序控制（SPC）的本地交换系统，1 ESS交换系统。由于采用了软件控制技术，使用户的呼叫业务（快速呼叫，呼叫等待，呼叫转移和三方通话等）的实现成为可能。1 ESS交换系统的第一套软件程序约为10万条指令，今天的交换系统则包括上千万条指令。第19页，本讲稿共90页The principle of converting analog signals to digital signals became popular with the introduction of pulse code modulation(
24、PCM);consequently,the known rate for telephone-quality speech(4kHz bandwidth)is 64kbps.3 During the 1960s and 1970s,a hierarchy of digital transmission channels based on the 64 kbps channel was established and still forms the backbone of todays digital network.One of the popular digital transmission
25、 systems is called the T1 carrier,which supports 24 voice channels,each 64 kbps,resulting in a total of 1.544 Mbps.第20页，本讲稿共90页 随着脉冲编码调制技术的出现，把模拟信号转换为数字信号的原理得到广泛应用；从而，对于电话质量的话音（4KHz带宽），公认的数字化速率为每秒64千比特。在六、七十年代，建立了基于64kbps的数字传输信道等级结构，它仍然是今天数字网的骨架。最通用的数字传输系统之一称为T1系统，它支持24路话音信道，每个信道速率为64kbps，这就产生了1.544
26、Mbps的总速率。第21页，本讲稿共90页Satellite communication was first proposed in 1945 by the British science fiction writer,Arthur C.Clarke.Satellite communications became a reality with the launching of the Russian satellite Sputnik(in 1957)and the American satellite Explorer(in 1958).The AT&T Telstar was the fi
27、rst experimental satellite capable of relaying television(TV)programs across the Atlantic Ocean.It was launched from Cape Canaveral(now Cape Kennedy)on July 1962.The first global civil communications satellite,INTELSAT(Early Bird),was launched in April 1965.第22页，本讲稿共90页卫星通信由英国科学幻想作家阿瑟克拉克于1945年首次提出。苏
28、联人造卫星（1957年）和美国探险号卫星(1958年)的发射使卫星通信成为现实。AT&T（美国电报电话公司）“电星”是第一颗能跨越大西洋传送电视节目的实验卫星。它于1962年7月从开普加拿瓦若（现在的开普肯尼迪）发射。第一颗全球民用通信卫星，国际通信卫星1号（晨鸟）则于1965年4月发射。第23页，本讲稿共90页The third phase of the evolution of communication networks occurred in the 1970s and is characterized by the introduction of data networks and
29、packet switching technology.The concept of packet switching was first published in a 1964 report by Paul Baran of the Rand Corporation for the U.S.Air Force.In 1966,under the sponsorship of the Advanced Research Project Agency(ARPA)of the U.S.Department of Defense(DoD),an experimental packet-switchi
30、ng network,ARPANET,was set up and was put into service in 1971.ARPANET led to the development and the widespread use of packet switching technology under the direction of LarryA.Roberts.Commercial offerings of packet-switched services rapidly followed the lead of the experimental networks,both in th
31、e United States and abroad.第24页，本讲稿共90页通信网发展的第三个阶段出现在七十年代，它是以数据网和分组交换技术的出现为特征的。分组交换的概念首先是兰德公司的保罗布朗于1964年在给美国空军的一个报告中提出的。1966年，由美国国防部（DoD）的高级研究计划局（ARPA）发起，建立了ARPANET分组交换实验网，并于1971年投入运营。ARPANET的出现导致了在拉里A罗伯特领导下的分组交换技术的发展和推广应用。分组交换技术的商用化随实验网之后在美国和国外迅速发展起来。例如，1973年波尔特，波拉拿克和纽曼（BBN）公司建立了Telenet，第一个公共分组交换网，
32、它把主计算机和拨号终端用户连接起来。第25页，本讲稿共90页 For example,in 1973,Bolt,Beraneck and Newman(BBN),Inc.founded TELENET,the first public packet-switched network,linking host computers and dial-up terminal users.The Canadian DATAPAC network was developed during the 19731977 period.The French Institute for information a
33、nd automatic research,in 1973,set up the CYCLADES and CIGALE networks.As data networks advanced from terminal-oriented systems to packet-switched,computer-to-computer linkups,the protocols necessary to make networks function also grew more complex.4 Two fundamental standards were essential for the a
34、dvancement in data networks.The first is the American Standard Code for Information Interchange(ASCII),which was approved in 1964 and became the common method of coding data for communications.The second standard is the Electronics Industries Association(EIA)recommended standard(RS)RS-232D.Its first
35、 version,issued in 1969,specified how the encoded information would be transmitted by modem over a telephone network.第26页，本讲稿共90页加拿大的DATAPAC网也是在1973至1977年期间发展起来的。法国信息和自动化研究院也于1973年建立了CYCLADES和CIGALE网络。由于数据网络从面向终端的系统向分组交换、计算机与计算机连接的方向发展，执行网络功能所必需的协议也变得愈来愈复杂。数据网有两个主要的基本标准。第一个是美国信息交换标准代码（ASCII），于1964年通
36、过且成为通信中对数据进行编码的公共方式。第二个是美国电子协会（EIA）建议的标准（RS）RS232D。它的第一个版本于1969年颁布。给出了编码信息通过调制解调器在电话网传送的方式。第27页，本讲稿共90页To achieve compatibility between computers and packet-switched networks,the International Telegraph and Telephone Consultative Committee(CCITT from the French acronym)established a world-standard p
37、rotocol,called X.25 in 1976.This led to several other international protocols for the interconnections between data networks.The widespread adoption of X.25 opened the door for the growth of packed-switched networks in the United States and other countries.Working closely with CCITT,the Internationa
38、l Organization of Standardization(ISO)in 1978 approved its seven-layer framework of protocols for data communications,called the open-system-interconnection(OSI)reference model.5 The purpose of the OSI reference model is to allow any computer anywhere in the world to communicate with any other,as lo
39、ng as both obey the OSI standards.第28页，本讲稿共90页为了解决计算机和分组交换网间的兼容性，国际电报电话咨询委员会（简称CCITT）于1976年建立了世界标准协议，称为X.25。这导致了各数据网间其它一些国际互连协议的产生。X.25的广泛采用在美国和其它国家打开了分组交换迅速发展的大门。与CCITT紧密协作的国际标准化组织（ISO）于1978年通过了用于数据通信的七层协议结构，称为开放系统互连（OSI）参考模型。OSI参考模型的目的是：只要遵循OSI标准，世界上任何地方的计算机都可以与任何其它计算机通信。第29页，本讲稿共90页This phase of
40、networking is also characterized by the introduction and wide acceptance of local area networks(LANs).The oldest and best known of all LANs is the Ethernet,which started as a laboratory project in 1974 by R.M.Metcalfe and his colleagues at Xerox Corporations Palo Alto Research Center.Ethernet was in
41、spired largely by ALOHANET,a packet-switched radio network developed by Norman Abramson at the University of Hawaii.The invention of the laser(which stands for light amplification by simulated emission of radiation)in 1959 led to major technical developments in the field of optical communication.In
42、1970,Corning Glass Works reported on the first low loss optical fiber(doped-silica clad fiber)that achieved 20dB/km loss.第30页，本讲稿共90页网络的这个阶段也可以用局域网（LANs）的出现并得到广泛使用作为特征。所有局域网中最早且最著名的网络是以太网，它是在1974年由R.M.梅特卡夫和他的同事们在静电印刷品公司的巴路奥特研究中心作为实验室项目开始的。以太网在很大程度上是受夏威夷大学诺曼阿布拉姆逊开发的无线分组网络Alohanet计算机网的激发产生的。1959年激光（激光
43、表示受激辐射光放大）的发明引起了光通信领域主要技术的发展。1970年康宁玻璃厂宣布制成了第一根低损耗光纤（掺杂石英包层光纤），其损耗达到20dB/km。第31页，本讲稿共90页The fourth phase of communication networking,which began in 1980,is characterized by the availability of the integrated services digital networks(ISDN)and mobile communications.ISDN can be regarded as a general-p
44、urpose digital network capable of supporting a wide range of services such as voice,data,and image.A key ingredient in ISDN is the provision of a common integrated digital access between the customers premises and the ISDN to support this multiplicity of services.Mobile communications entered a new
45、era with the introduction of the cellular concept.In 1981,the Federal Communications Commission(FCC)allocated 50 MHz of the spectrum(824849 MHz and 869894 MHz)to mobile radio cellular systems.By 1990,the U.S.cellular service has over five million subscribers.The four phases of the evolution of commu
46、nications networks are shown in Table 2.1.第32页，本讲稿共90页通信网的第四个阶段起始于1980年，是以综合业务数字网（ISDN）和移动通信的使用为特征的。ISDN可看作是能够支持如话音、数据和图像等各种业务的最终目的数字网。ISDN的一个关键要素是在用户和ISDN之间提供公共综合数字接入以支持各种各样的业务。蜂窝概念的出现使移动通信进入了一个新时期。1981年，联邦通信委员会（FCC）为移动无线蜂窝系统分配了50 MHZ的频谱（824849 MHZ和869894 MHZ）。到1990年，美国的蜂窝业务达500多万用户。第33页，本讲稿共90页第34
47、页，本讲稿共90页通信网发展的四个阶段见表2.1。表2.1 通信网发展的四个阶段 电话 数字网 数据网 综合数字网年代 十九世纪八十年代 六十年代 七十年代 八十年代业务类型 话音 话音 数据 话音，数据，图像，图形等交换技术 电路交换 电路交换 分组交换 电路、分组和快速分组交换（模拟）（数字）传输媒体 铜线，微波 铜线，微波，铜线，微波，铜线，微波，卫星，光纤 卫星 卫星第35页，本讲稿共90页KEY WORDS telecommunication 电信(讯)，无线电通讯telephony 电话(学)，通话switchboard(电话)交换台electromechanical 机电的，电动
48、机械的dialing pulse 拨号脉冲 crossbar 纵横，交叉 analog 模拟，模拟量radio-relay transmission 无线电中继传输high-frequency(HF)高频very-high-frequency(VHF)甚高频ultra-high-frequency(UHF)超高频repeater 转发器，中继器microwave 微波(的)quadrature 正交，90相位差第36页，本讲稿共90页quadrature amplitude modulation(QAM)正交幅度调制stored-program control(SPC)存储程序控制pulse
49、code modulation(PCM)脉冲编码调制hierarchy 分层，层次terminal 终端，终端设备protocol 协议，草案compatibility 兼容性，相容性interconnect 相互连接，互连open-system-interconnection(OSI)开放系统互连local area networks(LANs)局域网cellular 蜂窝状的，格形的，多孔的spectrum 频谱subscriber 用户copper 铜第37页，本讲稿共90页 converge on 集中于，聚集在上be regarded as 被认为是as long as 只要，如果
50、American Telephone and Telegraph(AT&T)美国电报电话(公司)Sputnik 人造地球卫星(苏卫星名)Explorer 美国陆军“探险者”卫星Telstar “电星”(美国通信卫星名)INTELSAT(international telecommunication satellite)国际通信卫星Advanced Research Project Agency(ARPA)(美国的)高级研究计划局the U.S.Department of Denfence(DoD)美国国防部ARPANET(Advanced Research Project Agency Net