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ФАЗА [ phase ] (Греч.: φάσις - появление; 1812).
1. Момент, этап в развитии какой-либо сущности или явления и/или характеристика (величина, выражение) этого момента или стадии.
Примеры: фаза колебания маятника, фаза болезни, фаза истории, фаза эволюции, фаза психического развития, запаздывание по фазе, сдвиг по фазе.
Соответствующие относительное (не имеющие степеней сравнения) прилагательные - фазовый и фазический.
Примеры: фазовый переход, фазовый фильтр, фазовый инвертор. Фазический - свойственный фазе, характерный фазе, связанный с фазой, синхронный с фазой, коррелирующий с фазой.
Пример: фазическое сокращение скелетной мышцы - сокращение мышцы синхронизированное с воздействием, коррелирующее с ним, когда фаза сокращения мышцы соответствует фазе воздействия.
2. Гомогенная часть системы, отделенная от других ее частей поверхностью раздела, при переходе через которую, свойства части изменяются скачком.
Примеры: газовая фаза системы (водяной пар, смесь газов в воздухе атмосферы), твердая фаза системы (лед), жидкая фаза (вода), система состоящая из нескольких фаз (вода со льдом, насыщенный раствор с осадком, уголь и сера в воздухе атмосферы).
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Схема. Сдвиг по фазе.
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Примечание:
(A) The fundamental of frequency f1.
(B) A second harmonic of frequency f2 = 2f1 and half the amplitude of f1. (C) The sum of f1 and f2
obtained by adding ordinates point by point. (D) A third harmonic of frequency f3 = 3f1 and half
the amplitude of f1. (E) The waveform resulting from the addition of f1, f2, and f3. All three
components are in phase, that is, they all start from zero at the same instant.
Harmonics.
A simple sine wave of a given amplitude and frequency, f1, is shown in Fig. 1-9A.
Figure 1-9B shows another sine wave f2 that is half the amplitude and twice the frequency.
Combining A and B at each point in time, the waveshape of Fig. 1-9C is obtained.
In Fig. 1-9D, another sine wave f3 that is half the amplitude of A and three times its frequency
is shown. Adding this to the f1 + f2 waveshape of C, Fig. 1-9E is obtained. The
simple sine wave of Fig. 1-9A has been progressively changed as other sine waves have
been added to it. |
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Whether these are acoustic waves or electronic signals, the process can
be reversed. The complex waveform of Fig. 1-9E can be disassembled, as it were, to the
simple f1, f2, and f3 sine components by either acoustical or electronic filters. For example,
passing the waveform of Fig. 1-9E through a filter permitting only f1 and rejecting f2 and
f3, the original f1 sine wave of Fig. 1-9A emerges in pristine condition.
The sine wave with the lowest frequency ( f1) of Fig. 1-9A is called the fundamental,
the sine wave that is twice the frequency ( f2) of Fig. 1-9B is called the second harmonic,
and the sine wave that is three times the frequency ( f3) of Fig. 1-9D is the third harmonic.
The fourth harmonic and the fifth harmonic are four and five times the frequency of the
fundamental, and so on. 4_5, p.9. |
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Примечание:
A rotation of 360° is analogous to one complete sine wave cycle.
Phase (1).
In Fig. 1-9, all three components, f1, f2, and f3, start from zero together. This is called an
in-phase condition. In some cases, the time relationships between harmonics or between
harmonics and the fundamental are quite different from this. We observed that one
revolution (360°) of the crankshaft of an automobile engine was equated with one cycle
of simple harmonic motion of the piston. The up-and-down travel of the piston spread
out in time traces a sine wave such as that in Fig. 1-10. One complete sine-wave cycle
represents 360° of rotation. If another sine wave of identical frequency is delayed 90°, its
time relationship to the first one is a quarter wave late (time increasing to the right). |
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A
half-wave delay would be 180°, and so on. For the 360° delay, the waveform at the bottom
of Fig. 1-10 synchronizes with the top one, reaching positive peaks and negative
peaks simultaneously and producing the in-phase condition.
In Fig. 1-9, all three components of the complex waveform of Fig. 1-9E are in phase.
That is, the f1 fundamental, the f2 second harmonic, and the f3 third harmonic all start at
zero at the same time. What happens if the harmonics are out of phase with the fundamental?
Figure 1-11 illustrates this case. The second harmonic f2 is now advanced 90°, and
the third harmonic f3 is retarded 90°. By combining f1, f2, and f3 for each instant of time,
with due regard to positive and negative signs, the contorted waveform of Fig. 1-11E is
obtained.
The only difference between Figs. 1-9E and 1-11E is that a phase shift has been
introduced between harmonics f2 and f3, and the fundamental f1. That is all that is needed
to produce drastic changes in the resulting waveshape. Curiously, even though the
shape of the waveform is dramatically changed by shifting the time relationships of the
components, the ear is relatively insensitive to such changes. In other words, waveforms
E of Figs. 1-9 and 1-11 would sound very much alike.
A common error is confusing polarity with phase. Phase is the time relationship
between two signals, while polarity is the +/- or the -/+ relationship of a given pair of
signal leads. 4_5, p.9. |
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Примечание:
(A) The fundamental
frequency f1. (B) The second harmonic f2 with twice the frequency and half the amplitude of f1 advanced
90° with respect to f1. (C) The combination of f1 and f2 obtained by adding ordinates point by point.
(D) The third harmonic f3 with phase 90° behind f1, and with half the amplitude of f1. (E) The sum of f1,
f2, and f3. Compare this resulting waveform with that of Fig. 1-9E. The difference in waveforms is due
entirely to the shifting of the phase of the harmonics with respect to the fundamental.
Phase (2).
In Fig. 1-9, all three components, f1, f2, and f3, start from zero together. This is called an
in-phase condition. In some cases, the time relationships between harmonics or between
harmonics and the fundamental are quite different from this. We observed that one
revolution (360°) of the crankshaft of an automobile engine was equated with one cycle
of simple harmonic motion of the piston. The up-and-down travel of the piston spread
out in time traces a sine wave such as that in Fig. 1-10. One complete sine-wave cycle
represents 360° of rotation. If another sine wave of identical frequency is delayed 90°, its
time relationship to the first one is a quarter wave late (time increasing to the right). |
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A
half-wave delay would be 180°, and so on. For the 360° delay, the waveform at the bottom
of Fig. 1-10 synchronizes with the top one, reaching positive peaks and negative
peaks simultaneously and producing the in-phase condition. |
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«Я У Ч Е Н Ы Й И Л И . . . Н Е Д О У Ч К А ?»
Т Е С Т В А Ш Е Г О И Н Т Е Л Л Е К Т А
Предпосылка:
Эффективность развития любой отрасли знаний определяется степенью соответствия методологии познания - познаваемой сущности.
Реальность:
Живые структуры от биохимического и субклеточного уровня, до целого организма являются вероятностными структурами. Функции вероятностных структур являются вероятностными функциями.
Необходимое условие:
Эффективное исследование вероятностных структур и функций должно основываться на вероятностной методологии (Трифонов Е.В., 1978,..., ..., 2015, …).
Критерий: Степень развития морфологии, физиологии, психологии человека и медицины, объём индивидуальных и социальных знаний в этих областях определяется степенью использования вероятностной методологии.
Актуальные знания: В соответствии с предпосылкой, реальностью, необходимым условием и критерием...
...
о ц е н и т е с а м о с т о я т е л ь н о:
— с т е п е н ь р а з в и т и я с о в р е м е н н о й н а у к и,
— о б ъ е м В а ш и х з н а н и й и
— В а ш и н т е л л е к т !
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