Unit 1
1.1)A. entertaining B. entertainment C. entertained D. entertainer
2)A. recognizable B. recognized C. recognition
3)A. tempting B. temptation C. tempt
4)A. reasoned B. reasoning C. reasonable D. reason
5)A. analyzed B. analytical C. analyst D. analysis
6)A. valuable B. valuation C. valued/values D. values
7)A. humorist B. humor C. humorous D. humorless
8)A. understandable B. understanding C. understand D. misunderstood
2. 1)a sense of responsibility 2)a sense of safety/security
3)a sense of inferiority 4)a sense of superiority
5)a sense of rhythm 6)a sense of justice
7)a sense of shame 8)a sense of helplessness
9)a sense of direction 10)a sense of urgency
3. 1)Lively behavior is normal 2)Fast cars appeal to
3)diverse arguments 4)I asked my boss for clarification
5)sensitive to light 6)Mutual encouragement
7)made fun of him 8)persist in his opinion/viewpoint
9)to be the focus/center of attention
10)we buy our tickets in advance
4. 1)certain/sure 2)involved 3)end 4)behavior
5)disciplining 6)agreed 7)individually 8)first
9)response 10)question 11)attempt 12)voice
13)directly 14)followed 15)trouble
Unit 2
1. Step One
throughout, upbeat/uplift, drawback, teenage,
handout/handwritten, birthday/birthstone, chairman, rag-eared, ever-ready, overdue/overage, long-distance,
self-conscious, mileage/milestone, typewriter/typewritten,
well-wishing/well-written
Step Two
1) long-distance 2) upbeat
3) ever-ready 4) overdue
5) typewriter 6) milestone
7) handwritten 8) uplifted
9) self-conscious 10) rag-eared
11) birthday 12) throughout
13) drawbacks 14) chairman
15) teenage
2.
1)intrigued/intrigue 2)straining/strain 3)savor/savored
4)treasure/treasure 5)credited/credit 6) boost/boost
7)note/noted 8)signed/sign 9)totalled/total 10) stuffed/stuff
11)count/count 12)last/last 13)complimented/compliment
14)flood/flooding 15)contact/contact
3. 1) thrives 2) strategy 3) annual
4) deserve 5) spontaneous
6) sincere 7) investment
8) enterprise 9) follow up
10) characterized 11) lingered
12) acknowledged
4. column: 1) D 2) A 3) B 4) C
tough: 1) D 2) B 3) E 4) F
5) C 6) A
5.1)complementary/ complimentary/ complimentary
2)stationery/stationary/stationary
3)typist/typewriter/typist 4)vulgar/vague/vague
5)pad/pat/pad 6)own/owed/owes/owned
6. 1) searched 2) clever 3) solution 4) wasted 5) tolerate 6) hidden 7) dumb 8) subject 9) noise 10) extra
Unit 3
1.
1. genetic
2. assign
3. noticeably
4. approved
5.Bias
6. deprived
7. constitute
8. participation
9. unintentional 10. postgraduate
2.
conscious--unconscious positive--negative
encourage--discourage superior—inferior directly—indirectly biased—fair
sexist—nonsexist limited—unlimited dependent—independent appropriately—inappropriately
3.1-4:CDAE 5-8:BCFB
4.
1. turn out
2. carry over
3. calling on
4. put away
5. fallen behind
6. take over
Unit 4
1.
1. confused, confusion
2. intelligence, intelligent
3. humorous, humor
4. strategy, strategic
5. motivated, motivation
6. combination, combined
7. creation, creative 8. pursuit, pursuing 9. multiplication, multiply
10. employ, employment
2.
1. perfected
2. approaching
3. value
4. functions
5. approach
6. perfect
7. honor
8. function
9. honor 10. value
3.
1. dismiss
2. consequences
3. promoting
4. applies
5. vital
6. scorned
7. conventional
8. original
4.
1. consciously
2. innovative
3. unconsciously
4. determines
5. Imagination
6. aware
7. control
8. created
9. extension 10. technique 11. vulnerable 12. unfolding 13. joyful 14. gain 15. Apply
Unit5
1.
1. A. necessity B. necessary C. necessarily
2. A. disagreement B. disagreed C. disagreeable
3. A. decisive B. decision C. decide
4. A. choosy B. choice C. chose
5. A. lead B. lead C. leading
6. A. perfect B. perfection C. perfected
7. A. determination B. determine C. determined
8. A. assist B. assistance C. assistant
9. A. imagination B. imaginative C. imaginary D. imaginable E. imagined
10. A. scared B. scary C. scared
11. A. tolerable B. tolerant C. tolerance D. tolerate
12. A. expectant B. expected C. expectations
2.
1. is bound to
2. follow her lead
3. goes too far/is going too far
4. take the place of
5. dropped out
6. have a fit
7. measure up to
8. look up to 9. Let’s face it 10. you name it
3.
1. outgrown
2. outdo
3. outwitted
4. outweigh
5. outlived
Unit 6
1.
1. sensible
2. relative
3. mechanism
4. requires
5. eliminate
6. crash
2.
1. character
2. end up
3. Rarely
4. casual
5. risky
6. all manner of
7. inform
8. sensible
9. definitively
3.
1. On the strength of
2. all manner of
3. feed on
4. reduce….to
5. end up
6. associate with
7. focus on
8. turned to
9. participate in 10. involved in
Unit 7
1.
Belief—doubt learn—unlearn
Deep—shallow shame--pride
Polite—rude/impolite useless--useful Inadequate—adequate well-informed—ill-informed Success—failure smart—dull
Boring—interesting painful—painless Dependent—independent imaginative—unimaginative Mediocre—excellent
2.
1. deprived of
2. for the sake of
3. get away with
4. dropped out
5. by no means
6. got down to
7. distinguish …. from
8. look back on
9. gone through 10. after all 11. be rid of 12. on my own
3.
1. choice
2. secure
3. hear
4. who
5. keep
6. while
7. now
8. This
9. pressure 10. expecting 11. tests 12. within 13. had 14. catch 15. marks 16. parents 17. obtain/get 18. teachers 19. relax 20. shape
Unit 8 P309
1.CEBDAF
2.rewrite rearrange replace reunite review reform readjust
3.BADAD CAAAB
P141
ABCAC BAACC BB
Unit 9P346
lution8)adaptable9)innovations10)objectivity
2.1)out of the ordinary2)preceded3)to be exact4)contradicted5)prosperity6)gave birth to7)catch our breath8)ad in mind9)proposed10)converted11)disastrous12)negative
3.1)she had hardly sat down
2)especially when you want to reserve a seat
3)is not necessarily the most useful
4)what sort of person do you have in mind
5)there’s a limit on the time
6)spent part of his childhood
7)three times of as many girls as boys
8)as do most of the people who live in this village
9)but on the other hand it would be sad to lose the family atmosphere
10)despite international pressure
P366
BABCB CCBAA BC
Unit10 P391
1. 1)A.bring down
B.brought in
C.bring back
D.bring about
E brought up
2)A going by
B gone down
C went off
D go about
E going around
3)A make of
B makes up for
C.made up
D.made for
E.make out
4)A thought nothing of
Bthink twice about
C thought better of
D thought highly of
5)A. on account of
B. on no account
C on that account
Dtake account of
Eby/from all accounts
2.1)d2)n3)f4)m5)g6)j7)b8)c9)e10)i11)l12)k13)a14)h
3.1)married2)later3)separated4)effective5)first6)signed7)suffering8)which9)claimed 10)meeting11)attended12)seated13)attaction14)finally15)almost16)by
P423
CCCBB BABBA ABBCC BCA
语法填空专项训练 1 Before the 17th century, most of the native English speakers lived in England. After the 17th century, British people began to move to other ___66___ (country). Gradually, English was spoken there. At present ___67___ (many) people speak English as their first, second or a foreign language than ever before. ___68___ (luck), native English speakers can understand each other even if they don’t speak the same kind of English. English ___69___ (change) and developed when cultures met and communicated with each other over the past centuries. The English ___70___ (speak) in England between about AD450 and 1150 was very different ___71___ the modern English we speak today. It was the new settlers that enriched the English language and ___72___ (especial) its vocabulary. The English language was settled by the 19th century ___73___ two big changes in English spelling happened. English now is also spoken as a foreign ___74___second language in South Asia. China may have the ___75___ (large) number of English learners. 66.【答案】countries 【解析】考查名词。country是可数名词，此处由other修饰用复数形式，指其他的国家。故填countries. 67. 【答案】more 【解析】考查比较级。根据句中的than ever before可知含有和以前比较的意思，要用比较级表示更多的人，故填more. 68. 【答案】Luckily 【解析】考查副词。此处单独使用作状语要用副词形式，指“幸运的是”，故填Luckily. 69. 【答案】has changed 【解析】考查时态。根据句意和时间状语over the past centuries可知与现在完成时连用，主语是单数，故填has changed. 70. 【答案】spoken 【解析】考查过去分词。English和动词speak是被动关系，此处是过去分词作定语，故填spoken.
第九章 数字电路基础知识 一、 填空题 1、 模拟信号是在时间上和数值上都是 变化 的信号。 2、 脉冲信号则是指极短时间内的 电信号。 3、 广义地凡是 规律变化的，带有突变特点的电信号均称脉冲。 4、 数字信号是指在时间和数值上都是 的信号，是脉冲信号的一种。 5、 常见的脉冲波形有，矩形波、 、三角波、 、阶梯波。 6、 一个脉冲的参数主要有 Vm 、tr 、 Tf 、T P 、T 等。 7、 数字电路研究的对象是电路的输出与输入之间的逻辑关系。 8、 电容器两端的电压不能突变，即外加电压突变瞬间，电容器相当于 。 9、 电容充放电结束时，流过电容的电流为0，电容相当于 。 10、 通常规定，RC 充放电，当t = 时，即认为充放电过程结束。 11、 RC 充放电过程的快慢取决于电路本身的 ，与其它因素无关。 12、 RC 充放电过程中，电压，电流均按 规律变化。 13、 理想二极管正向导通时，其端电压为0,相当于开关的 。 14、 在脉冲与数字电路中，三极管主要工作在 和 。 15、 三极管输出响应输入的变化需要一定的时间，时间越短，开关特性 。 16、 选择题 2 若一个逻辑函数由三个变量组成，则最小项共有（ ）个。 A 、3 B 、4 C 、8 4 下列各式中哪个是三变量A 、B 、C 的最小项（ ） A 、A B C ++ B 、A BC + C 、ABC 5、模拟电路与脉冲电路的不同在于( )。 A 、模拟电路的晶体管多工作在开关状态，脉冲电路的晶体管多工作在放大状态。 B 、模拟电路的晶体管多工作在放大状态，脉冲电路的晶体管多工作在开关状态。 C 、模拟电路的晶体管多工作在截止状态，脉冲电路的晶体管多工作在饱和状态。 D 、模拟电路的晶体管多工作在饱和状态，脉冲电路的晶体管多工作在截止状态。 6、己知一实际矩形脉冲，则其脉冲上升时间( )。 A 、.从0到Vm 所需时间 B 、从0到2 2Vm 所需时间 C 、从0.1Vm 到0.9Vm 所需时间 D 、从0.1Vm 到 22Vm 所需时间 7、硅二极管钳位电压为( ) A 、0.5V B 、0.2V C 、0.7V D 、0.3V 8、二极管限幅电路的限幅电压取决于( )。 A 、二极管的接法 B 、输入的直流电源的电压 C 、负载电阻的大小 D 、上述三项 9、在二极管限幅电路中,决定是上限幅还是下限幅的是( ) A 、二极管的正、反接法 B 、输入的直流电源极性 C 、负载电阻的大小 D 、上述三项 10、下列逻辑代数定律中，和普通代数相似是( ) A 、否定律 B 、反定律 C 、重迭律 D 、分配律
一 第二节语法填空(共10 小题；每小题 1.5 分，满分15 分) Once there lived a rich man 31 wanted to do something for the people of his town. 32 first he wanted to find out whether they deserved his help. In the centre of the main road into the town, he placed 33 very large stone. Then he 34 (hide ) behind a tree and waited. Soon an old man came along with his cow. “Who put this stone in the centre of the road? ”said the d o i l d d n m o a t n t r,y b t u o t r h e e m o v e the stone. Instead, with some difficulty he passed around the stone and continued on his way. 35 man came along and did the same thing; then another came ,and another. All of them complained about the stone but not tried to remove 36 . Late in the afternoon a young man came along. He saw the stone, 37 (say) to himself: “Thenight 38 (be) very dark. Some neighbors will come along later in the dark and will fall against the stone. ”Then he began to move the stone. He pushed and pulled with all his 39 (strong) to move it. How great was his surprise at last! 40 the stone, he found a bag of money. 第二节语法填空 31. who 32. But 33. a 34. hid 35. Another 36. it 37. saying 38. will be 39. strength 40. Under 二 第二节：语法填空（共10小题，每小题 1.5分，满分15分） The Internet is an amazing information resource. Students, teachers, and researchers use it as __31_ investigative tool. Journalists use it to find information for stories. Doctors use it to learn more about unfamiliar diseases and the 32_ (late) medical development. Ordinary people use it for shopping, banking, bill-paying, and communicating with family and friends. People all over the world use it to connect with individuals from _33 countries and cultures. However, __34____there are many positive developments __35__ (associate) with the Internet, there are also certain fears and concerns. __36___ concern relates to a lack of control over__37__ appears on the Internet. With television and radio there are editors to check the accuracy or appropriateness of the content of programs, and with television there are 38 (restrict) on what kinds of programs can __39__ (broadcast) and at what times of the day. With the Internet, parents cannot check a published guide to determine what is suitable __40____ their children to see. 第二节语法填空（共10 小题，每小题 1.5 分，满分15 分） 31. an 32. latest 33.other/different 34. while 35.associated 36. One 37. what 38. restrictions 39. be broadcast(ed) 40.for 三 第二节：语法填空(共10小题；每小题 1.5分，满分15分) Crying marriage? 31 (surprise), isn ’t it? Factually, the custom of crying marriage existed a long time ago in many areas of Southwest China ’Ssichuan Province, and 32 (remain) in fashion 33 the end of the Qing Dynasty. Though not so popular as before, the custom is still observed by people in many places, especially Tujia people, who view it as a 34 (necessary) to marriage procedure. It is very much 35 same in different places of the province. According to elderly people, every bride had to cry at the wedding. 36 , the bride ’nesighbors would look down upon 37 as a
数据通信基本知识 -------------------------------------------------------------------------- 所有计算机之间之间通过计算机网络的通信都涉及由传输介质传输某种形式的数据编码信号。传输介质在计算机、计算机网络设备间起互连和通信作用，为数据信号提供从一个节点传送到另一个节点的物理通路。计算机与计算机网络中采用的传输介质可分为有线和无线传输介质两大类。 一、有线传输介质(Wired Transmission Media) 有线传输介质在数据传输中只作为传输介质，而非信号载体。计算机网络中流行使用的有线传输介质(Wired Transmission Media)为：铜线和玻璃纤维。 1. 铜线 铜线(Copper Wire)由于具有较低的电阻率、价廉和容易安装等优点因而成为最早用于计算机网络中的传输介质，它以介质中传输的电流作为数据信号的载体。为了尽可能减小铜线所传输信号之间的相互干涉(Interference)，我们使用两种基本的铜线类型：双绞线和同轴电缆。 (1)双绞线 双绞线(Twisted Pair)是把两条互相绝缘的铜导线纽绞起来组成一条通信线路，它既可减小流过电流所辐射的能量，也可防止来自其他通信线路上信号的干涉。双绞线分屏蔽和无屏蔽两种，其形状结构如图1.1所示。双绞线的线路损耗较大，传输速率低，但价格便宜，容易安装，常用于对通信速率要求不高的网络连接中。 (2)同轴电缆 同轴电缆(Coaxial Cable)由一对同轴导线组成。同轴电缆频带宽，损耗小，具有比双绞线更强的抗干扰能力和更好的传输性能。按特性阻抗值不同，同轴电缆可分为基带(用于传输单路信号)和宽带(用于同时传输多路信号)两种。同轴电缆是目前LAN局域网与有线电视网中普遍采用的比较理想的传输介质。 2.玻璃纤维 目前，在计算机网络中十分流行使用易弯曲的石英玻璃纤维来作为传输介质，它以介质中传输的光波(光脉冲信号)作为信息载体，因此我们又将之称为光导纤维，简称光纤(Optical Fiber)或光缆(Optical Cable)。 光缆由能传导光波的石英玻璃纤维(纤芯)，外加包层（硅橡胶）和保护层构成。在光缆一头的发射器使用LED光发射二极管(Light Emitting Diode)或激光(Laser)来发射光脉冲，在光缆另一头的接收器使用光敏半导体管探测光脉冲。 模拟数据通信与数字数据通信 一、通信信道与信道容量(Communication Channel & Channel Capacity) 通信信道(Communication Channel)是数据传输的通路，在计算机网络中信道分为物理信道和逻辑信道。物理信道指用于传输数据信号的物理通路，它由传输介质与有关通信设备组成；逻辑信道指在物理信道的基础上，发送与接收数据信号的双方通过中间结点所实现的逻?quot;联系"，由此为传输数据信号形成的逻辑通路。逻辑信道可以是有连接的，也可以是无连接的。物理信道还可根据传输介质的不同而分为有线信道和
We all listen to music according to our separate , for the sake of analysis, the whole listening process may become clearer if we break it up into its component parts, so to certain sense we all listen to music on three separate lack of a better terminology, one might name these: 1) the sensuous plane, 2) the expressive plane, 3) the sheerly musical only advantage to be gained from mechanically splitting up the listening process into these hypothetical planes is the clearer view to be had of the way in which we listen. The simplest way of listening to music is to listen for the sheer pleasure of the musical sound is the sensuous is the plane on which we hear music without thinking, without considering it in any turns on the radio while doing something else andabsent-mindedly bathes in the kind of brainless but attractive state of mind is engendered by the mere sound appeal of the music. The surprising thing is that many people who consider themselves qualified music lovers abuse that plane in go to concerts in order to lose use music as a consolation or an enter an ideal world where one doesn’t have to think of the realities of everyday course they aren’t thinking about the music allows them to leave it, and they go off to a place to dream, dreaming because of and apropos of the music yet never quite listening to it. Yes, the sound appeal of music is a potent and primitive force, but you must not allow it to usurp a disproportionate share of your sensuous plane is an important one in music, a very important one, but it does not constitute the whole story. The second plane on which music exists is what I have called the expressive , immediately, we tread on controversial have a way of shying away from any discussion of music’s expressive not Stravinsky himself proclaim that his music was an “object”, a “thing”, with a life of its own, and with no other meaning than its own purely musical existenceThis intransigent attitude of Stravinsky’s may be due to the fact that so many people have tried to read different meanings into so many knows it is difficult enough to say precisely what it is that a piece of music means, to say it definitely to say it finally so that everyone is satisfied with your that should not lead one to the other extreme of denying to music the right to be “expressive”. Listen, if you can,to the 48 fugue themes of Bach’s Well-tempered to each theme, one after will soon realize that each theme mirrors a different world of will also soon realize that the more beautiful a theme seems to you the harder it is to find any word that will describe it to your complete , you will certainly know whether it is a gay theme or a sad will be able, on other words, in your own mind, to draw a frame of emotional feeling around your study the sad one a little closer. Try to pin down the exact quality of its it pessimistically sad or resignedly sad; is it fatefully sad or smilingly sadLet us suppose that you are fortunate and can describe to your own satisfaction in so many words the exact meaning of your chosen is still no guarantee that anyone else will be need they important thing is that each one feels for himself the specific expressive quality of a theme or, similarly, an entire piece of if it is a great work of art, don’t expect it to mean exactly the same thing to you each time you return to it. The third plane on which music exists is the sheerly musical the pleasurable sound of music and the expressive feeling that it gives off, music does exist in terms of the notes themselves and of their listeners are not sufficiently conscious of this third plane. It is very important for all of us to become more alive to music on its sheerly musical all, an actual musical material is being intelligent listener must be prepared to increase his awareness of the musical material and what happens to must hear the melodies, the rhythms, the harmonies, the tone colors in a more conscious above all he must, in order to follow the line of the composer’s thought, know something of the principles of musical to all of these elements is listening to the sheerly musical plane. Let me repeat that I have split up mechanically the three separate planes on which we listen merely for the sake of greater clarity. Actually, we never listen on one or the other of these we do is to correlate them—listening in all three ways at the same takes no mental effort, for we do it instinctively Perhaps an analogy with what happens to us when we visit the theater will make this instinctive correlation the theater, you are aware of the actors and actresses, costumes and sets, sounds and these give one the sense that the theater is a pleasant place to be constitute the sensuous plane in our theatrical reactions. The expressive plane in the theater would be derived from the feeling that you get from what is happening on the are moved to pity, excitement, or is this general feeling, generated aside from the particular words being spoken, a certain emotional something which exists on the stage,that isanalogous to the expressive quality in music. The plot and plot development is equivalent to our sheerly musical playwright creates and develops a character in just the same way that a composer creates and develops a to the degree of your awareness of the way in which the artist in either field handles his material will you become a more intelligent is easy enough to see that the theatergoer never is conscious of any of these elements is aware of them all at the same same is true of music simultaneously and without thinking listen on all three planes. It is not surprising that modern children tend to look blank and dispirited when info rmed that they will someday have to “go to work and make a living”. The problem is that they cannot visualize what work is in corporate Americ a. Not so long ago, when a parent said he was off to work, the child knew very well what was about to happen. His parent was going to make something or fix something. T
模拟电子技术复习资料总结 第一章半导体二极管 一.半导体的基础知识 1.半导体---导电能力介于导体和绝缘体之间的物质(如硅Si、锗Ge)。 2.特性---光敏、热敏和掺杂特性。 3.本征半导体----纯净的具有单晶体结构的半导体。 4.两种载流子----带有正、负电荷的可移动的空穴和电子统称为载流子。 5.杂质半导体----在本征半导体中掺入微量杂质形成的半导体。体现的是半导体的掺杂特性。*P型半导体:在本征半导体中掺入微量的三价元素（多子是空穴，少子是电子）。 *N型半导体: 在本征半导体中掺入微量的五价元素（多子是电子，少子是空穴）。 6.杂质半导体的特性 *载流子的浓度---多子浓度决定于杂质浓度，少子浓度与温度有关。 *体电阻---通常把杂质半导体自身的电阻称为体电阻。 *转型---通过改变掺杂浓度，一种杂质半导体可以改型为另外一种杂质半导体。 7. PN结 * PN结的接触电位差---硅材料约为0.6~0.8V，锗材料约为0.2~0.3V。 * PN结的单向导电性---正偏导通，反偏截止。 8. PN结的伏安特性 二. 半导体二极管 *单向导电性------正向导通，反向截止。 *二极管伏安特性----同ＰＮ结。 *正向导通压降------硅管0.6~0.7V，锗管0.2~0.3V。 *死区电压------硅管0.5V，锗管0.1V。 3.分析方法------将二极管断开，分析二极管两端电位的高低: 若V阳>V阴( 正偏)，二极管导通(短路); 若V阳 2) 等效电路法 直流等效电路法 *总的解题手段----将二极管断开，分析二极管两端电位的高低: 若V阳>V阴( 正偏)，二极管导通(短路); 若V阳 语法填空专题训练 Combined by Stella A Making new friends means 1_________(put) yourself out on a limb and asking others not only to accept you, but to like you and want to be around you as well. Unfortunately, there is no 2__________(magic) solution 3__________ this part of the process, so if you want to make friends, take a deep breath and jump right in! 4__________ first step to making new friends is figuring out what is holding you back. A lot of times people 5__________ are interested in making new friends don’t know why they don’t have them. They can’t see that 6__________ won actions are working against them. Once you can identify(确认，确定)what is keeping you from making new friends, you need to work through these concerns. This can be 7__________(pain) because you will need to put yourself outside of your comfort zones to see any real differences. The next step is to shine in these social settings so that others will leave with a positive impression. If you find social situations hard, just rely on a few simple rules. When you feel 8__________(confidence) that you’ve made some great new friends, get out there and celebrate with them! No matter 9__________ you decide to do, the important thing is to celebrate your new friends 10__________ hopefully continue cultivating more. B For your next vacation, why not think of 1__________(visit) Singapore? Singapore is a small city, and it doesn’t have nay beaches 2__________ mountains, but is has a very large zoo. It is also a 3__________(wonder) place for shopping. Don’t plan on driving a car in Singapore. The traffic 4__________(be) heavy in some parts of the city, and most private cars are not 5__________(allow) in downtown Singapore. 6_______ is easiest to get around the city 7_______ subway. 通信常识：波特率、数据传输速率与带宽的相互关系 【带宽W】 带宽，又叫频宽，是数据的传输能力，指单位时间能够传输的比特数。高带宽意味着高能力。数字设备中带宽用bps（b/s）表示，即每秒最高可以传输的位数。模拟设备中带宽用Hz表示，即每秒传送的信号周期数。通常描述带宽时省略单位，如10M实质是10M b/s。带宽计算公式为：带宽=时钟频率*总线位数/8。电子学上的带宽则指电路可以保持稳定工作的频率围。 【数据传输速率Rb】 数据传输速率，又称比特率，指每秒钟实际传输的比特数，是信息传输速率（传信率）的度量。单位为“比特每秒（bps）”。其计算公式为S=1/T。T为传输1比特数据所花的时间。 【波特率RB】 波特率，又称调制速率、传符号率（符号又称单位码元），指单位时间载波参数变化的次数，可以以波形每秒的振荡数来衡量，是信号传输速率的度量。单位为“波特每秒（Bps）”，不同的调制方法可以在一个码元上负载多个比特信息，所以它与比特率是不同的概念。 【码元速率和信息速率的关系】 码元速率和信息速率的关系式为：Rb=RB*log2 N。其中，N为进制数。对于二进制的信号，码元速率和信息速率在数值上是相等的。 【奈奎斯特定律】 奈奎斯特定律描述了无噪声信道的极限速率与信道带宽的关系。 1924年，奈奎斯特（Nyquist）推导出理想低通信道下的最高码元传输速率公式：理想低通信道下的最高RB = 2W Baud。其中，W为理想低通信道的带宽，单位是赫兹（Hz），即每赫兹带宽的理想低通信道的最高码元传输速率是每秒2个码元。对于理想带通信道的最高码元传输速率则是：理想带通信道的最高RB= W Baud，即每赫兹带宽的理想带通信道的最高码元传输速率是每秒1个码元。 符号率与信道带宽的确切关系为： RB=W(1+α)。 其中，1/1+α为频道利用率，α为低通滤波器的滚降系数，α取值为0时，频带利用率最高，但此时因波形“拖尾”而易造成码间干扰。它的取值一般不小于0.15，以调解频带利用率和波形“拖尾”之间的矛盾。 奈奎斯特定律描述的是无噪声信道的最大数据传输速率（或码元速率）与信道带宽之间的关系。 【香农定理】 香农定理是在研究信号经过一段距离后如何衰减以及一个给定信号能加载多少数据后得到了一个著名的公式，它描述有限带宽、有随机热噪声信道的最大数据传输速率（或码元速率）与信道带宽、信噪比（信号噪声功率比）之间的关系，以比特每秒（bps）的形式给出一个链路速度的上限。 语法填空题专项训练 阅读下面材料，在空白处填入适当的内容（1个单词）或括号内单词的正确形式。 1 When you start talking about good and bad manners you immediately start meeting difficulties. Many people just cannot agree to 1they mean. We asked a lady, who replied that she thought you could tell a well-mannered person by the way they occupied the space around them —for example, when such a person walks down a street he or she is 2(constant) aware of others. Such people never bump into other people. However, a 3(two) person thought that this was 4(much) a question of civilized behavior than good manners. Instead, this other person told us a story, which he said was quite well known, 5an American who 6(invite) to an Arab meal in one of the countries of the Middle East. The American hadn’t been told very much about the kind of food he might expect. If he had known about Arab food, he might have behaved 7 (good). Immediately before him was a very flat piece of bread that looked, to him, very much like a napkin (餐巾). 8(pick) it up, he put it into his collar, so that it fell across his shirt. His Arab host, 9had been watching, said nothing, but 10(immediate) copied the action of his guest. And that, said this second person, was a fine example of good manners. 2 There are times when people are so tired that they fall asleep almost anywhere. We can see a lot of people sleeping on the bus or train on their way home 1work in the evening. A man will be reading the newspaper, and seconds later it appears as if he is trying to eat it. Or he will fall asleep on the shoulder of the stranger sitting next to him. Another place where unplanned short sleep goes on is in the lecture hall 2 a student will start snoring so loudly that the professor has to ask another student 3(shake) the sleeper awake. A more 4(embarrass) situation occurs when a student starts falling into sleep and 5weight of the head pushes the arm off the desk, and the movement carries the rest of the body along. The student wakes up on the floor with no memory of getting there. The 6(bad) time to fall asleep is when driving. Police reports are full of 7(accident) that occur when people fall into sleep and go off the road. If the drivers are lucky, they are not 8(serious) hurt. One woman’s car, for example, we nt into the river. She woke up in four feet of water and thought that it 9(rain). When people are really 10 (tire), nothing will stop them from falling asleep — no matter where they are. 3 I decided a few months ago I was going to treat myself to a 4-day getaway from Los Angeles and visit Chicago. I booked an airplane ticket on a website. I also found a travel website where a discounted 3-night stay was purchased from a recently 1(open) hotel. About three weeks 2the trip, I had other plans and had to cancel the trip. Only then did I 3(realize) the room, while transferable to another person, couldn’t 4(change) to a later date and wasn’t refundable. I tried selling it but with no success. Five days before the “big weekend” I gave up 5(try) and decided I would contact some friends who lived in Chicago and would offer someone a free family vacation. After 6(contact) a handful of people, all of语法填空专题训练(含答案)
通信原理基础知识整理
语法填空专项训练
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