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Unit 91 In popular culture, the term UFO–or unidentified flying object–refers to a suspected alien spacecraft, although its definition encompasses any unexplained aerial phenomena. UFO sightings have been reported throughout recorded history and in various parts of the world, raising questions about life on other planets and whether extraterrestrials have visited Earth. They became a major subject of interest–and the inspiration behind numerous films and books–following the development of rocketry after World War II.通俗地说，所谓 UFO--或者不明飞行物--指疑似外星人的飞船，不过它的定义也包括无法解释的空中现象。
在全世界各地不同时期都有 UFO 目击的报告，引起人们关于外星生命以及地外生命是否访问过地球的争论。
在二战后火箭技术的发展下，它们成了人们感兴趣的一大主题--也是数不清的电影和书籍背后的灵感来源。
Flying Saucers2 The first well-known UFO sighting occurred in 1947, when businessman Kenneth Arnold claimed to see a group of nine high-speed objects near Mount Rainier in Washington while flying his small plane. Arnold estimated the speed of the crescent-shaped objects as several thousand miles per hour and said they moved “like saucers skipping on water.” In the newspaper report that followed, it was mistakenly stated that the objects were saucer-shaped, hence the term flying saucer.飞碟首个著名的飞碟目击事件发生在 1947 年，一个叫 Kenneth Arnold 的商人声称他在华盛顿的雷尼尔山附近玩小型飞机模型时看到了一组9个高速移动的物体。
Unit 9 Science and TechnologyToo Fast?People who were born just before World War I remember waving at automobiles as they passed. Seeing a car was like watching a parade—exciting and out of the ordinary. The airplane—it was spelled "aeroplane" then—was another new invention. Refrigerators were "iceboxes," and a man delivered the ice for the box in the summer and the coal for the stove in the winter. Now, the iceman, like the blacksmith, survives only in literature.Today, change comes so fast that working people can become obsolete because their occupations vanish in the middle of their lives. Knowledge, and thus the rate of change, increases geometrically. Every idea gives birth to a dozen new ones, and each of them has a dozen children. The people of the pre-World War I generation had hardly assimilated the inventions of that era before they were attacked by a new batch of even more sophisticated inventions. The Atomic Age dawned in 1945, August 6 to be exact, and then, before we could catch our breath, the Space Age arrived.Change was not always this rapid. Certain important inventions, like the telephone, the airplane, the automobile, and the radio, had been invented by 1914, but the effects of these inventions upon the lives of ordinary citizens were not felt until many years later. We now have the technology to develop machines before people are ready to use them. For example, we have the technology to enable people to pay their bills by phone—but even people with phones resist. The change is too much too fast. People don't want to talk to machines, especially if the machines talk back to them.It is certain that technology, especially computer technology, will rule our lives to a greater and greater degree. This situation will not necessarily prove positive or negative in effect. Many people would be more comfortable if change came more slowly, but on the other hand, there are many for whom every innovation is like a new toy. They can't wait for the next invention to be available. When scientists talk about the remarkably adaptable nature of people, they probably have these people in mind.But there is a limit to everyone's ability to adapt. What will happen to us when change comes so rapidly that we can no longer adjust to it? These same scientists who talk about our adaptable nature also tell us that change is to some degree emotionally painful to everyone. What then, will happen to us when change comes so rapidly that we can no longer stand the pain, and we refuse to change?We have read a lot about scientific and technological change, but that is only part of the picture of modern life. There is often a great lag between scientific discovery andcultural acceptance. For example, Charles Darwin's theory of evolution, proposed over one hundred years ago and accepted by all serious scholars for generations, is still rejected by large segments of society. These segments see science as contradicting a higher religious authority. They see science as questioning and destroying their beliefs and culture.The problem is not easily solved because it is in the nature of science to question, and it is in the nature of human beings not to want to question the things they believe in. Science is not merely a field of study like chemistry or physics or biology. Science is a method of looking at the world, a method that requires an open mind, objectivity, and proof based upon observation or experimentation. It is a method that ignores religion, race, nationality, economics, morality, and ethics. It pays attention only to the results of research. The scientific method has shown us endless marvels and wonders, but methods can't provide all the answers. Science cannot tell us whether or not to drop a bomb: That is a moral or political question. Science only tells us how to make one.As we have already said, technological innovations are being made at faster and faster rates. The future will be even more revolutionary than the past. Will we, as a species, survive the revolutions that we have begun? There is plenty of evidence to think that we will. Our species has enormous potential that we have just begun to use. For example, we have only begun to control the environment. One day technology will make every desert bloom. It's simple, really. To do so, all we need to do is lower the cost of converting sea water into fresh water. Then, when the deserts bloom, will they provide enough food for our growing numbers? Most likely, they will. We have only just begun to discover the possibilities of highly intensive desert agriculture. We already have the technology to increase production ten times and to use one-twentieth of the water we needed before.We know how to make agricultural miracles. What we need are the time and money to make the technology available to everyone.In the nineteenth century, people believed in progress. They believed that science would lead them to a new era of endless prosperity and happiness. Well, it didn't work out that way. Two disastrous world wars convinced people of that. Yet, in our disappointment and in our fears that science was a monster that would one day destroy us, we forgot that science was not the monster; we were the monster. Science was merely a servant, and like fire, a good servant when treated properly.Despite all the problems of the modern world, however, most people would not choose to live in any of the less scientific ages that have preceded ours. If—and this is abig if—we don't destroy ourselves in war, the future can only be better. Each year will bring a more bewildering array of scientific advances: diseases cured, space conquered, transportation and communication revolutionized, agriculture and industry completely transformed, etc. To some, the future sounds exciting; to others, frightening. But one thing is sure—it won't be boring.太快了？1 在第一次世界大战前夕出生的人仍然记得看到身边经过的汽车就挥手的情景。
1all elements are composed of scattered units called atoms,which are the smallest particles than show the characteristics of the element. atoms are tiny units of matter composed of positively charged protons, negatively charged elements ,and electrically neutral neutrons. protons and neutrons, which have almost the same mass,are clustered in the nucleus in the middle of the atom. electrons,which are tiny in comparison to the other units, move around the nucleus at high speed. atoms that have the same number of electrons and protons are electrically neutral. those that have got or lost electrons,and therefor are positively or negatively charged, are called ions.所有的元素都称为原子的散射单元，这是比显示的元件的特性的最小的颗粒组成。
原子是微小单位的物质组成的带正电的质子，带负电荷的元件和电中性的中子。
质子和中子，它们具有几乎相同的质量，聚集在细胞核内的原子在中间。
的电子，这在其他单位相比是微小的，围绕原子核高速移动。
具有相同的电子和质子数的原子是电中性的。
mobile and cellular radio移动和细胞广播in comparison to the relative stability and modest technical developments which are occurring in long haul wideband microwave communication systems there is rapid development and expanding deployment of new mobile personal communication system. These rang from wide coverage area pagers,for simple data message transmission,which employ common standards and hence achieve contiguous coverage over large geographical areas,such as all the major urban centres and transport routes in Europe,Asia or the continental USA.This chapter discusses the special channel characteristics of mobile systems and examines the typical cellular clusters adopted to achieve continuous communication with the mobile user.It then highlights the important properties of current,and emerging,TDMA and code division multiple access(CDMA), mobile digital cellular communication systems.Private mobile radioTerrestrial mobile radio works best at around 250 MHz as lower frequencies than this suffer from noise and interference while higher frequencies experience multipath propagation from buildings,etc,section 15.2.In practice modest frequency bands are allocated between 60MHz and 2GHz. Private mobile radio(PMR) is the system which is used by taxi companies,county councils,health authorities,ambulance services,fire services,the utility industries,etc,for mobile communications.PMR has three spectral at VHF,one just below the 88 to 108 MHz FM broadcast band and one just above this band with another allocation at approximately 170MHz.There are also two allocations at UHF around 450MHz. all these spectral allocations provide a total of just over 1000 radio channels with the channels placed at 12KHz channel spacings or centre frequency offsets. Within the 12khz wide channal the analogue modulation in PMR typically allows 7khz of bandwidth for the signal transmission.when further allowance is made for the frequency drift in the oscillators of these systems a peak deviation of only 2 to 3 khz is available for the speech traffic. Traffic is normally impressed on these systems by amplitude modulation or frequency modulation and again the receiver is of the ubiquitous superheterodyne design,Figure 1.4. A double conversion receiver with two separate local oscillator stages is usually required to achieve the required gain and rejection of adjacent channel signals.One of the problems with PMR receiver is that they are requiredto detect very small signals,typically—120dBm at the antenna output,corresponding to 0.2 uV,and,after demodulating this signal,produce ann output with perhaps 1W of audio equipment, the first IF is normally at10.7MHz and the second IF is very orten at 455KHz . unfortunately,with just over 1000 available channels for the whole of the UK and between 20000and30000issued licences for these systems,it is inevitable that the average busuness user will have to share the allocated channel with other companies in their same geographical area.There are various modes of operation for mobile radio communications networks, the simplest of which is singal frequency simplex. In simplex communication, traffic is broadcast, or one way. PMR uses half duplex(see later Table 15.3) where, at the end of each transmission period, there is a handover of the single channel to the user previously receiving, in order to permit them to reply over the same channel. This is efficient in that it requires only one frequency allocation for the communication link but it has the disadvantage that all units canhear all transmissions provided they are within rage of the mobile and frequencies are allocated for the transmissions. One frequency is used for the forward or downlink, namely base-to-mobile communications. This permits simultaneous two-way communication and greatly reduces the level of interference, but it halves other’s transmissions, which can lead to contention with two mobiles attempting to initiate a call, at the same time, on the uplink in a busy syetem.Although PMR employs relatively simple techniques with analogue speech transmission there have been many enhancements to these systems over the years . Data transmission is now in widespread use in PMR systems using FSK modulation. Data transmission also allows the possibility of hard copy graphics output and it gives direct access to computer services such as databases, etc. Data prembles can also be used, in a selective calling mode, when initiating a transmission to address a special receiver and thus obtain more privacy within the system.15.4.5 Trunked radio for paramilitary use集群无线电的军事使用Another related TDMA mobile radio standard is the European trunked radio(TETRA)network which has been developed as part of the public safety radio communications service(PSRCS) for use by police, utilities, customs office, etc. TETRA in fact is part of wider international collaborations for paramilitary radio use.In these portable radios there is a need for frequency hopping (FH) to give an antieavesdropping capability and encryption for security of transmission to extend military mobile radio capabilities to paramilitary use, i.e. for police, customs and excise offices, etc. these capabilities are included in the multiband interteam radio for the associated public safety communications office in the USA while Europe has adopted the TETRA standard.TETRA is essentially the digital TDMA replacement of the analogue PMR systems. The TETRA standard has spectrum allocations of 380 to 400 and 410 to 430MHz, with the lower band used for mobile transmissions and the upper band for base station use. TETRA mobile have 1 W output power and the base stations 25 W using error with the data throughput rate varying, to meet the required quality of service. TETRA can accommodate up to four users each with a basic speech or data rate of 7.2kbit/s. with coding and signaling overheads, the final transmission rate for the four-user slot is 36 kbit/s. this equipment is large and more sophisticated than a commercial cell phone, and it sells for a very much higher price becase the production runs are much small. However, its advanced capabilities are essential for achieving paramilitary communications which are secure from eavesdropping.15.5 Code division multiple accessAnalogue communication systems predominantly adopt frequency division multiple access (FDMA), where each subscriber is allocated a narrow frequency slot within the available channel. The alternative TDMA(GSM) technique allocates the entire channel bandwidth to a subscriber but constrains the subscriber but constrains the subscriber to transmit only regular short bursts of wideband signal. Both these accessing techniques are well established for long haulterrestrial, satellite and mobile communications as they offer very good utilization of the available bandwidth.15.5.1The inflexibility of these coordinated accessing techniques has resulted in the development of new systems based on the uncoordinated spread spectrum concept. In these systems the bits of slow speed data traffic from each subscriber are deliberately multiplied by a high chip rate spreading code, forcing the low rate (narrowband data signal) to fill a wide channel bandwidth.15.7.2 3G systemsThe evolution of the third generation (3G)system began when the ITU produce the initial recommendations for a new universal mobile telecommunications system(UMTS)[www.] The 3G mobile radio service provides higher data rate services ,with a maximum data rate in excess of 2Mbit/s, but the achievable bit rate is linked to mobility. Multimedia applications encompass services such as voice, audio/video, graphics, data, Internet access and e-mail. These packet and circuit switched services have to be supported by the radio interface and the network subsystem.Several radio transmission technologies(RTT) were evaluated by the ITU and adopted into the new standard, IMT-2000. the European standardization body for 3G, the ETSI Special Mobile Group, agreed on a radio access scheme for 3G UMTS universal terrestrial radio access(UTRA) as an evolution of GSM. UTRA consists of two modes : frequency division duplex(FDD) where the uplink and downlink are transmitted on different frequencies; and time division duplex(TDD) where the uplink and downlink are time multiplexed onto the same carrier frequency. The agreement assigned the unpaired bands (i.e. for UTRA TDD ). TD-CDMA is a pure CDMA based system. Both modes of UTRA have been harmonised with respect to basic system parameters such as carrier spacing, chip rate and frame length to ensure the interworking of UTRA with GSM.The 3G proposal were predominantly based wideband CDMA(WCDMA) and a mix of FDD and TDD access techniques. WCDMA is favoured for 3G in poor propagation environments with a mix of high modest speed data traffic. It is generally accepted that CDMA is the preferred accesstechnique and, with the increase in the data rate, then the spreading modulation needs to increase to wideband transmission.WCDMA is based on 3.84Mchip/s spreading codes with spreading ratio, i.e. , K values, of 4-256 giving corresponging data ratas of 960-15 kbit/s. the upper FDD uplink band I from 1920-1980 MHz is paired with a 2110-2170 MHz downlink. In addition uplink bands II & III at 1850-1910 MHz and 1710-1785 MHz are also paired, respectively, with 1930-1990 MHz and 1805-1880 MHz allocations. the system is configured on a 10 ms frame with 15 individual slots to facilitate TDD as well as FDD transmissions. TDD is more flexible as time-slots can be dynamically reassigned to uplink and downlink functions, as required for asymmetric transfer of large files or video on demand traffic. 3G WCDMA systems use an adaptive multirate speech coder with encoded rates of 4.75-12.2 kbit/s. receivers commonly use the easily integrated direct conversion design, in place of the superheterodyne design . receiver sensitivities are typically -155dBm.The 3GPP2 standard aims to achieve a wide area mobile wireless packet switched capability with CDMA2000 1×EV DO revision A (sometimes called IS-856A). Here 1×refers to the single carrier 1.25 Mchip/s system. It achieves a 3.1 Mbit/s downlink and a delay sensitive services. The 3GPP standard has gone through many release with R4 in 2001 which introduced packet data services and R6 in 2005 to further increase the available data transmission rate . R6 pioneers the use of high-speed downlink packet access and multimedia broadcast multicast services which offer reduced delays and increased uplink data rates approaching 6 Mbit/s.In parallel with the European activities extensive work on 3G mobile radio was also performed in Japan. The Japanese standardisation body also chose WCDMA, so that the Japanese and European proposals for the FDD mode were already aligned closely. Very similar concepts have also been adopted by the North American standardization body.In order to work towards a global 3G mobile radio standard, the third generation partnership project(3GPP), consisting of members of the standardization bodies in Europe, the USA, Japan, Korea and China, was formed. It has merged the already well harmonized proposals of the regional standardization bodies to work on a common 3G international mobile radio standard, still called UTRA. The 3GPP Project 2(3GPP2), on the other hand, works towards a 3G mobile radio standard based on cdmaOne/IS-95 evolution, originally called CDMA2000.比起相对稳定、适度的技术发展是发生在宽带微波通信系统,有长期快速发展和扩大部署的新的移动个人通讯系统。
Sentence TranslationUnit 1Text A1.However, the volume of business done on the Internet is growing rapidly, as people orderbooks and other products to make money transactions.但是，因特网上的交易数量急速增长，人们从网上购书和其他的产品，进行资金交易。
2.They use them to prowl the Internet, looking for ways to break into computers systems runby banks, telephone companies and even government departments.他们用电脑上网，寻找能够进入银行电脑系统、电话公司的电脑系统、甚至是政府的电脑系统的方式。
3.The first indication of a security breach may be when a customer discovers a fraudulentmoney transaction on a credit card account.当顾客发现信用卡的帐号上出现了来历不明的消费时，这可能就是安全受到了破坏的第一个标志。
4.The use of credit cards to buy things on the Internet converts the issue of Internet securityinto one of general security.用信用卡在网上购物使网络安全变成了大众所普遍关注的安全的一种5.Few people think twice about giving a credit card number over the phone and many areequally careless about what happens to the carbon copy when completing a transaction over the counter.很多人会在电话里随意报出自己的信用卡号码，同样地，也有很多人不留意交易完成后放在银行柜台上的副本。
科技英语考试题型与分值Part I Match the words with their definition. Fill the number of the word in the bracket. (5%) 10个小题，每题0.5分。
Part II Translate English phrases to Chinese or Chinese ones to English.(30%)30个小题，每题1分。
1-20英译汉，21-30汉译英。
Part III. Translate the following sentences. (40%)10个句子，每个句子4分。
1-5英译汉，6-10汉译英。
Part IV. Reading comprehension (25%)A. Answer the following questions according to the articles in the textbook.(15%)5个问题，每题3分。
B．Choose the best answer from the four choices given. (10%)5个选择题，每题2分。
Unit 1 练习答案及课文译文Part 2 Reading AI1 F2 T3F 4T5T 6.F 7.T 8.T 9.F 10.TII1. Reducing the time and cost of product development and production.2. The product cycle is composed of two main processes：the design process and the manufacturing process．3. The activities involved in the design process can be classified largely as two types：synthesis and analysis．4. Rapid prototyping is becoming popular because this technology enables the construction of a prototype by deposition layers from the bottom to the top．5. This includes the preparation of drawings，reports，and bills of materials.III1.d2.e3.b4.j5.i6.c7.f8.h9.g 10.aIV1.处理速度2.用户友好的交互图形3. 产品周期4. 设计规格5. 设计评价6.CAD7.CAM8.CAE9.design process 10.production processV1. 除非能以较低的价格提供更好的质量及更短的交货时间提供新产品，否则任何企业都无法在当今的国际竞争中立足。
The power plant is the heart of a ship. 动力装置是船舶的心脏。
The power unit for driving the machines is a 50-hp induction motor.驱动这些机器的动力装置是一台50马力的感应电动机。
Semiconductor devices, called transistors, are replacing tubes in many applications.半导体装置也称为晶体管,在许多场合替代电子管。
Cramped conditions means that passengers’legs cannot move around freely.空间狭窄,旅客的两腿就不能自由活动。
All bodies are known to possess weight and occupy space. 我们知道，所有的物体都有重量并占据空间。
The removal of minerals from water is called softening. 去除水中的矿物质叫做软化。
A typical foliage leaf of a plant belonging to the dicotyledons is composed of two principal parts: blade and petiole.Einstein’s relativity theory is the only one which can explain such phenomena.All four (outer planets) probably have cores of metals, silicates, and water.The designer must have access to stock lists of the materials he employs.设计师必须备有所使用材料的储备表。
