vacuum

vac·uum

V5003800 (văk′yo͞om, -yəm, -yo͞o-əm)n. pl. vac·uums or vac·u·a (-yo͞o-ə) 1. a. Absence of matter.b. A space empty of matter.c. A space relatively empty of matter.d. A space in which the pressure is significantly lower than atmospheric pressure.2. A state of emptiness; a void.3. A state of being sealed off from external or environmental influences; isolation.4. pl. vac·uums A vacuum cleaner.adj.1. Of, relating to, or used to create a vacuum.2. Containing air or other gas at a reduced pressure.3. Operating by means of suction or by maintaining a partial vacuum.tr. & intr.v. vac·uumed, vac·uum·ing, vac·uums To clean with or use a vacuum cleaner.

[Latin, empty space, from neuter of vacuus, empty, from vacāre, to be empty; see euə- in Indo-European roots.]

vacuum

(ˈvækjʊəm) n, pl vacuums or vacua (ˈvækjʊə) 1. (General Physics) a region containing no matter; free space. Compare plenum³2. (General Physics) a region in which gas is present at a low pressure3. (General Physics) the degree of exhaustion of gas within an enclosed space: a high vacuum; a perfect vacuum. 4. a sense or feeling of emptiness: his death left a vacuum in her life. 5. short for vacuum cleaner6. (General Physics) (modifier) of, containing, measuring, producing, or operated by a low gas pressure: a vacuum tube; a vacuum brake. vbto clean (something) with a vacuum cleaner: to vacuum a carpet. [C16: from Latin: an empty space, from vacuus empty]

vac•u•um

(ˈvæk yum, -yu əm, -yəm)

n., pl. -u•ums for 1,2,4-6, -u•a (-yu ə) for 1,2,4,6; n. 1. a space entirely devoid of matter. 2. an enclosed space from which matter, esp. air, has been partially removed so that the matter or gas remaining in the space exerts less pressure than the atmosphere (opposed to plenum). 3. the state or degree of exhaustion in such an enclosed space. 4. a space not filled or occupied; emptiness; void: The loss left a vacuum in his life. 5. vacuum cleaner. adj. 6. of, pertaining to, employing, or producing a vacuum. 7. (of a hollow container) partly exhausted of gas or air. 8. noting or pertaining to canning or packaging in which air is removed from the container to prevent deterioration of the contents. v.t. 9. to clean with a vacuum cleaner. v.i. 10. to use a vacuum cleaner. [1540–50; < Latin, neuter of vacuus empty]

vac·uum

(văk′yo͞om)1. A condition in which there is no matter or very little matter.2. An enclosed space, such as the space inside a container, in which there are far fewer gas molecules than in an equal volume of the air outside it. A vacuum has a much lower gas pressure than that of the atmosphere at sea level.

vacuum

Past participle: vacuumed
Gerund: vacuuming

Imperative
vacuum
vacuum

Present
I vacuum
you vacuum
he/she/it vacuums
we vacuum
you vacuum
they vacuum

Preterite
I vacuumed
you vacuumed
he/she/it vacuumed
we vacuumed
you vacuumed
they vacuumed

Present Continuous
I am vacuuming
you are vacuuming
he/she/it is vacuuming
we are vacuuming
you are vacuuming
they are vacuuming

Present Perfect
I have vacuumed
you have vacuumed
he/she/it has vacuumed
we have vacuumed
you have vacuumed
they have vacuumed

Past Continuous
I was vacuuming
you were vacuuming
he/she/it was vacuuming
we were vacuuming
you were vacuuming
they were vacuuming

Past Perfect
I had vacuumed
you had vacuumed
he/she/it had vacuumed
we had vacuumed
you had vacuumed
they had vacuumed

Future
I will vacuum
you will vacuum
he/she/it will vacuum
we will vacuum
you will vacuum
they will vacuum

Future Perfect
I will have vacuumed
you will have vacuumed
he/she/it will have vacuumed
we will have vacuumed
you will have vacuumed
they will have vacuumed

Future Continuous
I will be vacuuming
you will be vacuuming
he/she/it will be vacuuming
we will be vacuuming
you will be vacuuming
they will be vacuuming

Present Perfect Continuous
I have been vacuuming
you have been vacuuming
he/she/it has been vacuuming
we have been vacuuming
you have been vacuuming
they have been vacuuming

Future Perfect Continuous
I will have been vacuuming
you will have been vacuuming
he/she/it will have been vacuuming
we will have been vacuuming
you will have been vacuuming
they will have been vacuuming

Past Perfect Continuous
I had been vacuuming
you had been vacuuming
he/she/it had been vacuuming
we had been vacuuming
you had been vacuuming
they had been vacuuming

Conditional
I would vacuum
you would vacuum
he/she/it would vacuum
we would vacuum
you would vacuum
they would vacuum

Past Conditional
I would have vacuumed
you would have vacuumed
he/she/it would have vacuumed
we would have vacuumed
you would have vacuumed
they would have vacuumed

vacuum

A space without matter.

Thesaurus

Noun	1.	vacuum - the absence of mattervacuityemptiness - the state of containing nothing
	2.	vacuum - an empty area or space; "the huge desert voids"; "the emptiness of outer space"; "without their support he'll be ruling in a vacuum"vacancy, void, emptinessspace - an empty area (usually bounded in some way between things); "the architect left space in front of the building"; "they stopped at an open space in the jungle"; "the space between his teeth"
	3.	vacuum - a region that is devoid of mattervacuityregion, part - the extended spatial location of something; "the farming regions of France"; "religions in all parts of the world"; "regions of outer space"
	4.	vacuum - an electrical home appliance that cleans by suctionvacuum cleanerdust bag, vacuum bag - a bag into which dirt is sucked by a vacuum cleanerhome appliance, household appliance - an appliance that does a particular job in the homeHoover - a kind of vacuum cleaner
Verb	1.	vacuum - clean with a vacuum cleaner; "vacuum the carpets"hoover, vacuum-cleanclean, make clean - make clean by removing dirt, filth, or unwanted substances from; "Clean the stove!"; "The dentist cleaned my teeth"

vacuum

noun1. gap, lack, absence, space, deficiency, void The collapse of the army left a vacuum in the area.2. emptiness, space, void, gap, empty space, nothingness, vacuity The spinning turbine creates a vacuum.3. vacuum cleaner, Hoover (trademark), vac (Brit. informal) Get the breakfast and take the vacuum round the house before the boys wake.verb1. vacuum-clean, hoover I vacuumed the carpets today.Quotations
"Nature abhors a vacuum" [François Rabelais Gargantua]

vacuum

noun1. Total absence of matter:emptiness, vacancy, vacuity, void.2. Empty, unfilled space:barrenness, emptiness, nothingness, vacancy, vacuity, void.3. A desolate sense of loss:blankness, desolation, emptiness, hollowness, void.

Translations

吸尘用真空吸尘器打扫真空真空吸尘

vacuum

(ˈvӕkjuəm) noun1. a space from which (almost) all air or other gas has been removed. 真空2. short for vacuum cleaner. verb to clean (something) using a vacuum cleaner. She vacuumed the carpet.用真空吸尘器打扫vacuum cleaner a machine that cleans carpets etc by sucking dust etc into itself. 真空吸尘器ˈvacuum flask noun a container with double walls that have a vacuum between them to keep the contents from losing or gaining heat. a (vacuum-)flask of hot coffee.保温瓶

vacuum

→ 吸尘zhCN, 真空吸尘zhCN

vacuum

vacuum,

theoretically, space without matter in it. A perfect vacuum has never been obtained; the best human-generated vacuums contain less than 100,000 gas moleculesmolecule
[New Lat.,=little mass], smallest particle of a compound that has all the chemical properties of that compound. A single atom is usually not referred to as a molecule, and ionic compounds such as common salt are not made up of molecules.
..... Click the link for more information. per cc, compared to about 30 billion billion (30×10¹⁸) molecules for air at sea level. The most nearly perfect vacuum exists in intergalactic space, where it is estimated that on the average there is less than one molecule per cubic meter. In ancient times the belief that "nature abhors a vacuum" was held widely and persisted without serious question until the late 16th and early 17th cent., when the experimental observations of Galileo and the Italian physicist Evangelista Torricelli demonstrated its essential fallacy. Torricelli obtained a nearly perfect vacuum (Torricellian vacuum) in his mercury barometerbarometer
, instrument for measuring atmospheric pressure. It was invented in 1643 by the Italian scientist Evangelista Torricelli, who used a column of water in a tube 34 ft (10.4 m) long.
..... Click the link for more information. . A common but incorrect belief is that a vacuum causes "suction." Actually the apparent suction caused by a vacuum is the pressure of the atmosphere tending to rush in and fill the unoccupied space. There are various methods for producing a vacuum, and several different kinds of vacuum pumps have been devised for removing the molecules of gas or vapor from a confined space. In the rotary oil-sealed pump a rotor turning in a cylinder allows gas to enter through an inlet valve from a space to be evacuated and then pushes it through an outlet valve into the atmosphere. In the oil or mercury diffusion pump, gas enters the pump through an inlet and is then swept toward an outlet by heavy, fast-moving oil or mercury vapor molecules. The outlet is connected to a rotary pump that expels the gas into the atmosphere. A cryogenic pump removes gas from a container by condensing the gas molecules on an extremely cold surface in the container. An ion pump consists of a chamber containing a source of electrons that are used to bombard gas molecules from a container to be evacuated. Collisions between the electrons and gas molecules ionize the molecules, causing them to be drawn to, and held by, a collector in the pump. The first vacuum pump was invented by the German physicist Otto von Guerricke in 1650. There are many practical applications of vacuums in industry and scientific research, e.g., in vacuum distillation, vacuum processing of food, in devices such as the vacuum tube, vacuum bottle, and barometer, and in research machines.

Vacuum

the state of a gas at a pressure considerably lower than that of the atmosphere. The concept of a vacuum is usually applied to a gas that fills a limited volume, but it is often also applied to gas in open space—for example, in the cosmos. The behavior of gas in vacuum devices is determined by the relationship between the free-path length λ of the molecules (or atoms) and the dimension d characteristic for the given instrument or process. These dimensions may be, for example, the distance between the walls of a vacuum space, the diameter of a vacuum conduit, or the distance between electrodes in an electrical-vacuum instrument. Vacuums are classified as follows, according to the relationship of λ to d: low vacuum (λ≪d), medium vacuum (λ~d), and high vacuum (λ≫d).

In vacuum installations and instruments of dimension d ~ 10 cm, the pressure range greater than 10² newtons per sq m (N/m²) or 1 mm Hg corresponds to low vacuum; 10² to 10^-1 N/m² (1 to 10^-3 mm Hg), to medium vacuum; and less than 0.1 N/m², to high vacuum. The pressure range less than 10^-6 N/m² (10^-8 mm Hg) is called ultrahigh vacuum. However, in pores or canals with diameter d ~ 1 micron, the behavior of gas corresponds to that of a high vacuum beginning at 10³ N/m² (a few dozen mm Hg), but in chambers for the simulation of outer space with dimensions reaching dozens of meters, the boundary between medium and high vacuum is considered to be a pressure of 10^-3 N/m²(10^-5 mm Hg).

The highest degree of vacuum attainable by existing methods corresponds to pressures of 10^-13 to 10^-14 N/m²(10^-15 to 10^-16 mm Hg). Under these circumstances a volume of 1 cu cm contains only a few dozen molecules. The degree of rarefaction attained is determined by the equilibrium between the rate of evacuation of the gas and the rate at which it enters the evacuated space. Entry may occur because of penetration of gas into the vacuum chamber from the outside through microscopic openings (leaks), and also as a result of the emission of gas adsorbed by the walls or dissolved in them.

The properties of a gas under conditions of low vacuum are determined by the frequent collisions of gas molecules with each other, which are accompanied by energy exchange among them. Such a gas has internal friction (viscosity); its flow is subject to the laws of aerodynamics. Phenomena of transfer (electrical conductivity, heat conduction, internal friction, or diffusion) under conditions of low vacuum are characterized by smooth change or constancy of the gradient of the transferred quantity. For example, the temperature of a gas in the space between the “hot” and “cold” walls in a low vacuum changes gradually. In addition, the quantity of heat (heat conduction) or matter (diffusion) transferred does not depend on pressure. If the gas is in two communicating vessels with different temperatures, the pressures in these vessels are equal at equilibrium. When there is passage of a current in a low vacuum, the ionization of gas molecules plays a determining role.

In a high vacuum the properties of a gas are determined by the collisions of its molecules with the walls. Collisions between gas molecules occur rarely and play a secondary role. The movement of molecules between the walls is rectilinear (molecular mode of gas flow). Transfer phenomena are characterized by the appearance on the walls of a jump in the gradient of the transferred quantity—for example, in the total space between the hot and cold walls, approximately half of the molecules have a velocity corresponding to the temperature of the cold wall, and the other half have a velocity corresponding to that of the hot wall (that is, the average temperature of the gas in the total space is the same and is different from that of either the hot or the cold wall). The quantity of transferred heat, matter, and so on is directly proportional to the gas pressure. The gas pressures p₁ and p₂ in communicating vessels of different absolute temperatures T₁ and T₂ are determined by the relationship .

The passage of a current through a high vacuum is possible only as a result of the emission of electrons and ions by the electrodes. The ionization of gas molecules here plays a secondary role. It is substantial in cases where the free-path length of charged particles is artificially increased and becomes significantly greater than the distance between electrodes or when there is fluctuating movement of the particles around any electrode.

The properties of a gas in a medium vacuum are intermediate between its properties in high and low vacuums.

The characteristics of ultrahigh vacuums are due not to mutual collisions of particles but to other processes on the surfaces of solid bodies in the vacuum. The surface of any body is always covered with a thin layer of gas, which can be removed by heating (outgassing). The surface properties of bodies change sharply after outgassing: the friction coefficient is greatly increased, in a number of cases the welding of certain materials becomes possible even at room temperature, and so on. The layer of gas that has been removed is gradually restored as a result of the adsorption of the gas molecules bombarding the surface; this is accompanied by a change in its surface properties. The formation of a monomolecular layer of gas is sufficient to change these properties. The time t necessary to form such a layer in a vacuum is inversely proportional to the pressure. When pressure p = 10^-4 N/m² (10^-6 mm Hg), t = 1 sec; at other temperatures the time t (in seconds) may be estimated according to the formula t = 10^-6p, where p is the pressure in mm Hg, or according to the formula t = 10^-4p, where p is the pressure in N/m². These formulas are correct if every molecule of gas that hits the surface remains on it (if the capture coefficient is equal to 1). In a number of cases the capture coefficient is less than 1, and the time of formation of the monomolecular layer increases accordingly. When p < 10^-6 N/m² (10^-8 mm Hg), the formation of a monomolecular layer of gas occurs over a period of more than several minutes. An ultrahigh vacuum is defined as one in which, during the period of observation, there is no essential change in the properties of the surface (which was initially free of gas) as a result of its interaction with gas molecules.

A. M. RODIN

Vacuum

in physics, a medium in which there are no particles of matter and no field. In technology, a medium in which there are “very few” particles is called a vacuum. The fewer particles per unit volume of such an atmosphere, the higher the vacuum. However, a complete vacuum—a medium in which there are no particles at all—is not “nothingness” devoid of all properties. The absence of particles in a physical system does not mean that it is absolutely empty and nothing occurs within it.

The contemporary concept of the vacuum took shape within the framework of the quantum field theory. In the microcosm described in quantum theory, wave-particle duality occurs: all particles (molecules, atoms, elementary particles) have some wave properties and all waves have some particle properties (corpuscles). In quantum field theory, all particles—including the corpuscles of light waves, photons —perform on identical bases as quanta of their corresponding physical fields. The photon is a quantum of the electromagnetic field; the electron and proton are quanta of the electron-positron field; mesons are quanta of the meson, or nuclear, field, and so forth. The physical magnitudes characteristic of the particles are associated with each quantum: mass, energy, momentum, electrical charge, spin, and others. The state of the system and of its physical characteristics is completely determined by the number of particles in it—the quanta—and their individual states. Specifically, in any quantum system there is a vacuum state in which the system contains absolutely no particles (quanta). In this state, the energy of the system assumes the smallest possible value, and the charge, spin, and other quantum numbers that characterize the system equal zero. These facts are intuitively clear: inasmuch as there are no material carriers of physical properties in the vacuum state, it would seem that in such a state the values of all physical magnitudes should equal zero. But in quantum theory the uncertainty principle operates, according to which only a portion of the physical magnitudes of the system may simultaneously have precise values; the remaining magnitudes prove to be indeterminate. (Thus, precise assignment of the pulse of a particle entails complete indeterminacy of its coordinates.) Therefore, in any quantum system all the physical magnitudes cannot simultaneously be exactly equal to zero.

For example, among the magnitudes that cannot be assigned exactly and simultaneously are the number of photons and the intensity of the electrical (or magnetic) field. Strict recording of the number of photons leads to scattering (fluctuations) in the magnitude of the intensity of the electrical field in relation to some average value (and vice versa). If the number of photons in the system is precisely equal to zero (in the vacuum state of the electromagnetic field), then the intensity of the electrical field has no definite value: the field will undergo fluctuations all the time, although the average (observed) value of intensity will be equal to zero. All the other physical fields—the electron-positron field, the meson field, and so forth—are also subject to such fluctuations.

In quantum field theory fluctuations are interpreted as the production and destruction of virtual particles (that is, particles that are continually produced and immediately destroyed), or virtual quanta of a given field. The presence of fluctuations does not affect the values of the total electrical charge, the spin, and other characteristics of the system, which, as already stated, are equal to zero in the vacuum state. However, virtual particles participate in interactions exactly as real particles do. For example, a virtual photon is capable of producing a virtual electron-positron pair; this is analogous to the production of a real electron-positron pair by a real photon. Because of fluctuations, a vacuum acquires special characteristics that are manifested in observed effects; consequently, the vacuum state follows all the laws that apply to “real” physical states.

Let us examine a system that consists only of one real electron. There are no real photons in such a system, but fluctuations of the photon vacuum (this term means the absence of real photons) lead to the production of “clouds” of virtual photons near the electron and electron-positron pairs following the photons. Such pairs appear in the same way as bound charges in a dielectric: under the action of the coulomb field of the real electron they are polarized, and they screen (that is, effectively decrease) the charge of the electron. By analogy with the dielectric, the effect of screening the electrical charge of virtual particles is called vacuum polarization.

As a result of vacuum polarization, the electrical field of a charged particle is slightly different from its coulomb field at short distances from the particle. Thus, for example, the energy levels of electrons closest to the nucleus of an atom are displaced. Vacuum polarization also influences the behavior of charged particles in a magnetic field. The magnetic momentum of the particle, which characterizes this behavior, varies in total from its ‘’normal” value, which is determined by the mass and spin of the particle. Corrections of the energy levels as well as of the magnetic momentum amount to fractions of a percent, and theoretically calculated values agree with very great precision with experimental measurements.

V. P. PAVLOV

vacuum

[′vak·yəm] (physics) Theoretically, a space in which there is no matter. Practically, a space in which the pressure is far below normal atmospheric pressure so that the remaining gases do not affect processes being carried on in the space. (quantum mechanics) The lowest possible energy state of a system, conceived of as a polarizable gas of virtual particles, fluctuating randomly.

vacuum

1. a region containing no matter; free space 2. a region in which gas is present at a low pressure 3. the degree of exhaustion of gas within an enclosed space 4. of, containing, measuring, producing, or operated by a low gas pressure

vacuum

vac·uum

vacuum

vac•u•um

vac·uum

vacuum

vacuum

vacuum

vacuum

vacuum

vacuum

vacuum

in a vacuum

nature abhors a vacuum

Nature abhors a vacuum.

vacuum something out

vacuum something up (from something)

in a vacuum

do something in a ˈvacuum

nature abhors a vacuum

vacuum

vacuum,

Vacuum

Vacuum

vacuum

vacuum

vacuum

vacuum

vac·uum

vac·u·um

vac·u·um

VACUUM

vacuum

Synonyms for vacuum

noun gap

Synonyms

noun emptiness

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noun vacuum cleaner

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verb vacuum-clean

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Synonyms for vacuum

noun total absence of matter

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noun empty, unfilled space

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noun a desolate sense of loss

Synonyms

Synonyms for vacuum

noun the absence of matter

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Related Words

noun an empty area or space

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noun a region that is devoid of matter

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noun an electrical home appliance that cleans by suction

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verb clean with a vacuum cleaner

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