Доставка цветов в Севастополе: SevCvety.ru
Главная -> Английский язык

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 [91] 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148

missile (A). In most cases tlie telemetry transmitter, used for other purposes, is sufficient. However, for special applications a compact stable signal source is also available. There are two signal paths to the ground receiver (B). One is the direct one. The other path Is through a receiver-transmitter combination in the target (C). To differentiate between these two signal paths, the signal through the target Is shifted in frequency. The two signals are then compared in the ground station receiver. As long as the system is stationary, the difference frequency between the two paths will be a constant. If the missile and the target are in relative motion to each other, the difference frequency-will exhibit the typical Doppler characteristic shown in Fig. 2.

The Doppler system is often chosen, since for the majority of missions it has several advantages.

This system has some problems. The first problem is that of data reduction. While the reduction of ideal data is quite simple, the data actually obtained may be difficult to interpret. Curve В in Fig. 2 shows the effect of noise, the Intercept occurring at a distance of about 80 miles from the ground station. Curve С shows the effect of pulse reversal in the missile antenna lobes. This causes a discontinuity in the curve.

There are other.more subtle changes in the Doppler curve, which are caused by acceleration of the missile or the target as shown in Curve D.

e. A FIRST LOOK AT RANDOM NOISE

(Для перевода со словарем)

Synopsis: Ttie aim of this paper is to discuss some elementary properties of a type of noise which has been called "Gaussian" or "random". The power spectrum is discussed and its relation to the autocorrelation function is pointed out. Two probability distributions associated with the noise are described.

Occasionally one encounters engineering problems which involve the random fluctuations of an electric current or voltage, or some other quantity. These fluctuations are often called "noise". A considerable amount of information about such fluctuations has been obtained by mathematicians who have studied the subject under the name of "stochastic processes". The aim of this paper is to present an introduction to the subject by mentioning some of the main properties of the fluctuations, which in accordance with engineering usage, will be spoken of as noise.

.There is a wide variety of noises, but this paper will be restricted to those called "stationary processes". That is, they go on about the same forever, and their statistical properties do not change with time. Furthermore, the discussion wi 1 be concerned mostly with a special kind of noise which has been called "random" or "Gaussian" noise. Its second name comes from the fact that its statistical properties are closely related to the Gaus-



sian distribution used in probability theory. Random noise is a mathematical idealization of certain types of noise occurring in nature. One such type is thermal noise, which occurs as a result of the thermal agitation of electrons in a conductor.

Noise consisting of impulses that can be heard separately is not considered to be random noise in the sense that the term will be used here. For example, noise from relay clicks and ignition noise from automobile engines are not random noises. When such trains of impulses are expressed as Fourier series or as Fourier integrals there is a considerable amount of correlation between the phases of the various components. This is not true for random noise.

Why are engineers interested in the properties of noise? One reason is that noise produces interference in transmission systems. A knowledge of the statistics of the noise is helpful In estimating the quality of a proposed system while it is still in the design stage. In some cases the noise is large in comparison with the signal, as in the problem of detecting airplanes or submarines. The question here is how best to overcome the noise. Again, carrier communication systems are coming into use which employ a wide band of frequencies to transmit a large number of telephone channels. The output of such a system resembles random noise, and this fact may be used in designing the system.

Random noise has been studied more extensively than other types of noise. The probable reason for this is tliat it is easier to handle mathematically than the other types. Furthermore, some frequently encountered noises, such as thermal noise in conductors and shot-noise in vacuum tubes, are close approximations to random noise.

КОНТРОЛЬНЫЕ ВОПРОСЫ

1. Укажите способ перевода конструкции "to have the engines Installed" (§ 108).

2. Как переводится глагол to have в конструкции "to have the body move" (§ 109)?



УПРАЖНЕНИЯ ПО ОТДЕЛЬНЫМ ВОПРОСАМ ПЕРЕВОДА

1. Переведите предложения. Обратите внимание на то, что прн переводе предложения, состоящего из подлежащего и сказуемого (без дополнения и обстоятельств), подлежащее часто ставится после сказуемого.

Подлежащее в данном английском предложении является главным для сообщения. В противоположность английскому языку главное для сообщения в русском языке обычно стоит в конце предложения.

Примерная схема предложения: «Делается то-то».

1. Further studies of the solar radiation are needed.

2. When monatomic hydrogen reassociates into the normal molecular form a great deal of energy is released.

3. Within recent years the application of radio techniques in the study, of various problems of astronomy has led to remarkable results. A new science, Radio Astronomy, has emerged.

4. Detailed Information on different types of particle accelerators- the heavy artillery of the atomic world shooting invisible bullets at invisible targets - is now available.

5. The temperature of the upper atmosphere may be calculated if the local speed of sound is known.

6. Thermoelectric generators with power ratings from a few watts to 50 kilowatts have been developed and generators with ratings of hundreds or thousands of kilowatts are being considered.

2. Переведите предложения. Обратите внимание на то, что при переводе предложения, состоящего из обстоятельства (стоящего на первом месте), подлежащего и сказуемого (без дополнения), подлежащее, как правило, ставится после сказуемого. Укажите, какое это имеет смысловое значение.

Примерная схема предложения: «Тогда-то (там-то) делается то-то».

1. In radio calculations the metric system Is used.

2. About 1940 another circular accelerator, the betatron, was developed.

3. In a voltmeter high current sensitivity is desired.

4. To improve fuels light metals such as lithium, boron, and beryllium are being added.



0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 [91] 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148



0.0056
Яндекс.Метрика