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# period

Timing specification from synchronization element to synchronization element.

Cycle is a Chinese vocabulary, pronounced zhōu qī, from "Jing Zhai Ancient and Modern". If a group of events or phenomena repeats in the same order, the time or space interval to complete this group of events or phenomena is called a cycle.

## Catalogues

### Word concept

Basic explanation

[period;cycle] In the process of movement and change of things, certain characteristics appear repeatedly, and the time elapsed for two consecutive appearances is called "cycle".

The period of the pendulum.

Citation explanation

1. In the process of movement, change and development of things, certain characteristics appear repeatedly, and the time elapsed for two consecutive appearances is called cycle.

Yuan Lizhi's "Jing Zhai Ancient and Modern Times" Volume 1: "Yin and Yang match, but young and old must be equal. The strategy of dryness, two hundred and ten has six, the old Yang is also; the strategy of Kun, four hundred and forty, old Yin is also. If the old yin and the old yang are three hundred and sixty, the day of the cycle is also."

2. When the object is in reciprocating motion or the physical quantity changes repeatedly, repeat the elapsed time.

The time required for alternating current to complete a periodic change is called the cycle of alternating current.

3. Anniversary.

Zeng Guofan's "Book of Chen Huchen" in the Qing Dynasty: "The amount of the country's vassals has moved to the land, and the cycle has been reached. The land is barren and the people are poor and there is no facility.

4. The Tibetan calendar.

The years, months and days of all Yaos, no matter whether they are calculated according to the solar day, lunar day or palace day, have their parallelism. Starting from the first year, month and day, after several rotations, its parallelism will return to an integer without surplus or deficiency. The value of this time is called the period (that is, the time required for a celestial body to return to a certain relative position is The sidereal period of the celestial body).

5. In chemistry, it often refers to a series of elements in each row of the periodic table.

The periodic table is divided into 7 periods. The first cycle (contains only 2 elements) is called a very short cycle; the second and third cycles (each containing 8 elements) are called a short cycle; the fourth and fifth cycles (each containing 18 elements) are called a long cycle; the sixth , 7 cycles (including 32 kinds of elements), the 7th cycle (not all discovered yet) is called the special long cycle. There are also the first, second, and third cycles as short cycles, and the fourth, fifth, sixth, and seventh cycles as long cycles.

6. The historian's concept of cycle is basically an empirical concept, which is far from theological and philosophical concepts. In the most general sense of historical research, cycle refers to the recurring state of a certain historical phenomenon and level of movement and change.

### Math cycle

The time required to complete a vibration is called the period of vibration.

If f(x) is a periodic function, then the smallest positive number l that makes f(x+l)=f(x) holds for any x in the domain is called the (fundamental) period of f(x).

In a computer, the time required to complete a cycle; or the time required to access a memory, also known as the cycle [4]. The essence of periodic function: When the overall difference of the two independent variable values is equal to a multiple of the period, the overall function value of the two independent variable values is equal. For example: f(x+6) = f(x-2) then the function period is T=8.

### Chemical cycle

1. A classification of elements in the periodic table. A series of elements with the same number of electron layers are arranged in an increasing order of atomic number, one horizontal line is one cycle. From left to right of the same period elements, the metallicity gradually weakens, and the non-metallicity gradually increases.

2. Refers to a series of elements with the same number of electron layers and arranged in order of increasing atomic number. There are seven horizontal rows in the periodic table, that is, seven periods. The first cycle (contains only 2 elements) is called a very short cycle; the second and third cycles (each containing 8 elements) are called a short cycle; the fourth and fifth cycles (each containing 18 elements) are called a long cycle; the sixth , 7 cycles (including 32 kinds of elements), the 7th cycle (not all discovered yet) is called the special long cycle. There are also the first, second, and third cycles as short cycles, and the fourth, fifth, sixth, and seventh cycles as long cycles.

### Physical cycle

1. Uniform circular motion is a periodic motion. Periodicity means that the moving object repeatedly returns to its original position after a certain period of time, and the instantaneous speed repeatedly returns to its original size and direction. The time it takes for an object in a uniform circular motion to move for one week is called a period.

Period is also a physical quantity that describes the speed of uniform circular motion. Long period indicates slow motion of the object, and short period indicates fast motion of the object.

2. When the object is in reciprocating motion or the physical quantity changes repeatedly, repeat the elapsed time. The time it takes for an object or physical quantity (such as alternating current, voltage, etc.) to complete a vibration (or oscillation). In various periodic motions or periodic changes, an object or physical quantity changes from any state, and after a period or an integer multiple of the period, it always returns to the initial state.

3. The time required for an alternating current to complete a complete change is called a cycle, and is often represented by T. The unit of period is second (s), and milliseconds (ms) or microseconds (μs) are also commonly used as units.

### Biological cycle

The spontaneous or passive activity of the object itself, from the beginning to the end is called a cycle. The biological cycle is like the movement of celestial bodies. The earth revolves around the sun for one year. Biological cell division is a cycle starting from the inter-division period when the cell is ready to divide, passing through the prophase, mid-term, post-phase, and terminal period, and finally back to the inter-division period.

### Economic cycle

The business cycle is also known as the "business cycle" and "business cycle". In the UK, it is usually called the "trade cycle"; in Japan, it is usually called the "business cycle". The economic cycle refers to the cyclical fluctuations in the operation of the national economy, which are falling together, expanding and contracting continuously. In the past, it was divided into four stages: prosperity, recession, depression, and recovery, generally called recession, trough, expansion, and peak.

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