專業(yè)外語-信號與噪音 第7講

1、Lecture 7 Signals and Noise (II)Grammar 介詞在科技英語中的用法較多，它常與名詞、動詞或-形容詞等搭配構(gòu)成介詞短語，也可構(gòu)成短語介詞，其作用相當(dāng)于單個介詞。 熟悉科技英語中常用的介詞與其他詞類的習(xí)慣搭配是正確理解詞義的一種重要手段。1 1介詞與動詞、名詞、形容詞搭配介詞與動詞、名詞、形容詞搭配與動詞(絕大部分及物)構(gòu)成短語動詞，要求后接賓語。 例如：apply to，arise from，consist of，deal with，depend on/upon，relate to，result in，differ from，follow from， lead

2、 to，lie in，vary with等。 例例11 A complex variables is composed of a real part alpha and an imaginary part beta.復(fù)變量，由實部 和虛部 組成。 例例22 Most discrete-time signals arise from sampling continuous-time signals多數(shù)離散時間信號是由連續(xù)時間信號采樣而來。imdinriimaginary：sampling s:mpli與形容詞連用，構(gòu)成短語形容詞，其語法功能類似過去分詞，常用做后置定語例如：analogous t

3、o，applicable to，capable of，different from，essential to，equivalent to，familiar with，full of，identical to，independent of, proportional to，similar to，suitable for，superior to等。 analogous nlgs 相似的capable keipbl 有能力的 例例33 The power gain in decibels is equal to 10times the logarithm base l0 of the power g

4、ain用分貝表示的功率增益等于10乘以以10為底的功率增益的對數(shù)。 例例44 A CT signal is also called an analog signal because its waveform is often analogous to that of the physical variable 由于連續(xù)時間信號的波形常與對應(yīng)物理變量的波形相似，所以也常稱其為模擬信號。與名詞連用構(gòu)成短語名詞，例如：anything but，1ack of，nothing but，numbers of，plenty of，reduction to，something wrong with，rati

5、oto, advantage over, problem with等。 例例55 This section deals with the advantages of transistors over electron tubes本節(jié)討論晶體管與電子管相比其所具有的優(yōu)點。 2 2常用短語介詞常用短語介詞短語介詞可當(dāng)做介詞使用，常用短語介詞包括according to，along with，apart from，as to/for, because of, but for, by means of，due to，in accordance with，in addition to，in case o

6、f，in proportion to，in spite of, instead of, on account of，owing to，with reference to，with regard to，up to等。 例例66 The convolution integral and its use in fixed linear system analysis by means of the principle of superposition are treated in Chapter2第2章講述應(yīng)用疊加原理求解卷積積分及其在恒定線性系統(tǒng)分析中的應(yīng)用。 例例7 7 This book ha

7、s all three major analysis methods: mesh, loop, and nodal, along with explanations of the advantages and disadvantages of each 該書介紹了三種主要的電路分析方法，即網(wǎng)孔法、環(huán)路法與節(jié)點法，并比較其優(yōu)劣。 例例88 By this definition, no work is done by holding a box in a hand(根據(jù)，按照，后接表示規(guī)則、慣例、標(biāo)準(zhǔn)等詞，常用在推導(dǎo)中) 根據(jù)這一定義，把一只盒子拿在手中并沒有做功。 例例99 Since powe

8、r is proportional to the square of the voltage，if the input signal is increased by a factor of two，the output signal is increased by a factor of four (與數(shù)詞連用，表示相差的數(shù)量) 由于功率與電壓的平方成正七巳如果輸入信號是原來的2倍，輸出信號則為原來的4倍。 3 3常用介詞的特殊用法常用介詞的特殊用法 by definin 例例1010 By a family of curves is meant a specified set of curv

9、es which satisfy given conditions 所謂曲線簇，是指能滿足已知條件的一組特殊的曲線。 例例1111 In contrast，multiplying a signal by another signal is nonlinear(與multiply, divide等連用表示“乘以，除以”) 相反，將一個信號與另一個信號相乘是非線性的。 例例1212 For the sake of accuracy and convenience，the magnetic effect is utilized almost universally in electric measu

10、ring instrument (常與purpose；sake，interest，benefit，good等連用，表目的)為準(zhǔn)確與方便起見，電子測量儀器幾乎普遍使用磁效應(yīng)。 例例1313 It is necessary for us to solve this equation for x (與solve連用表示方程所要求解的對象) 我們必須從這個方程解出x。 for kjursi 例例1414 Semiconductor devices are very small in size and light in weight(后接抽象名詞，做狀語)半導(dǎo)體器材體積小，重量輕。 例例1515 Vol

11、tage is expressed numerically in volts(以，用，后接表示方式的計量單位、語言等)用伏特表示電壓。 in 例例1616 The inclusion of Re causes a decrease in amplification(在表示數(shù)量變化的名詞后多用in) 接入Re會使放大倍數(shù)降低。 例例1717 The study of sound is of importance not only in music and speech，but also in communication and industry(表示描述關(guān)系，具有(性質(zhì)或特點)，等效于對應(yīng)的形容

12、詞，但語氣更強)研究聲音不僅對音樂和語言，而且對通信和工業(yè)都有重要意義。 例例1818 The physicist made an important discovery in the year of 1977(表示同位關(guān)系)1977年，這個物理學(xué)家有一個重要發(fā)現(xiàn)。 of 例例1919 A signal is a description of how one parameter varies with another parameter(A of B結(jié)構(gòu)，AB為動賓關(guān)系，修飾的名詞A由及物動詞變來) 信號用以描述一個參量如何隨另一個參量的變化而變化。 例例2020 The change of

13、electrical energy into mechanical energy is done in motors(A of B結(jié)構(gòu)，BA為主謂關(guān)系，修飾的名詞B是由不及物動詞而來)電能轉(zhuǎn)換為機械能是通過電動機實現(xiàn)的。 例例2121 The flip-flop will change the stored information only upon application of proper control signal(一就，在 之后，后接具有動詞含義的名詞或動名詞)只有施加了合適的控制信號后，該觸發(fā)器才能改變儲存的信息。 onupon 例例2222 Radio waves travel

14、through most types of matter with ease (等效于對應(yīng)副詞，語氣更強)無線電波通過大多數(shù)物質(zhì)很容易。 with 例例2323 With a sine wave input, the technician would look to see if the output is also a sine wave(對于，就而言，用于句首)技術(shù)員想要知道，對于正弦輸入，輸出信號是否也是正弦波。 teknin 例例2424 With all disadvantages this design is considered to be one of the best(盡管，

15、與a11連用)盡管有其缺點，這一設(shè)計仍被認(rèn)為是最佳設(shè)計之一。 例例25 25 Lamps are lighted with switch on.(等效于when the switch is turned on)開關(guān)閉合燈點亮。Texts Mathematical models that violate some or all of the conditions listed previously are often used. and for one main reason- to simplify the mathematical analysis. For example, conside

16、r the digital waveform shown in Figure 3-1. The mathematical model waveform has discontinuities at the switching times. This situation violates the third condition that the physical waveform is continuous. The physical waveform is of finite duration, but the duration of the mathematical waveform ext

17、ends to infinity. consider knsidcondition kndinfinite fainaitcontinuous kntinjusviolate vt.違犯, 冒犯, 干擾switching 開關(guān)，轉(zhuǎn)換，交換，配電duration n. 持續(xù)時間, 周期discontinuity n. 中斷，不連續(xù)infinity n. 無限vaileit djureindiskntinju(:) iti infiniti In other words, this mathematical model assumes that the physical waveform has

18、existed in its steady-state condition for all time. Spectral analysis of the model will approximate the correct results, except for the extremely high-frequency components. The average power that is calculated from the model will give the correct value for the average power of the physical signal th

19、at is measured over an appropriate time interval. The total energy of the mathematical models signal will be infinity because it extends to infinite time, whereas that of the physical signal will be finite. Consequently, the model will not give the correct value for the total energy of the physical

20、signal without the us of some additional information. However. the model can be used to evaluate the energy of the physical signal over some finite time interval. This mathematical model is said to be a power signal because it has the property of finite power (and infinite energy), whereas the physical waveform is said to be an energy signal because it has finite energy. 1. 總而言之，波形常分為信號或噪聲、數(shù)字總而言之，波形常分為信號或噪聲、數(shù)字的或模擬的、確定性的或的或模擬的、確定性的或非確定性的非確定性的（nondeterministic） 、物理上可實現(xiàn)的或、物