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单词 absorption
释义
absorption

Physics
  • 1. The take-up of a gas by a solid or liquid, or the take-up of a liquid by a solid. Absorption differs from adsorption in that the absorbed substance permeates the bulk of the absorbing substance.

    2. The conversion of the energy of electromagnetic radiation, sound, streams of particles, etc., into other forms of energy on passing through a medium. A beam of light, for instance, passing through a medium may lose intensity because of two effects: scattering of light out of the beam, and absorption of photons by atoms or molecules in the medium. When a photon is absorbed, there is a transition to an excited state.


Astronomy
  • The transfer of energy from a photon to an atom or molecule. If the energy of the photon is just sufficient to raise an electron from one energy level to another, the result is an absorption line at a particular wavelength; this is called a bound–bound transition. Absorption at a wide range of wavelengths is called continuous absorption, and occurs when the absorbed photons have energies greater than the minimum needed to eject an electron completely; this is called a bound–free transition, or photoionization. Absorption may occur whenever radiation traverses a gas, for example the outer layers of a star, the Earth’s atmosphere, a nebula, or interstellar space (see Interstellar Absorption).


Chemistry
  • 1. (in chemistry) The take up of a gas by a solid or liquid, or the take up of a liquid by a solid. Absorption differs from adsorption in that the absorbed substance permeates the bulk of the absorbing substance.

    2. (in physics) The conversion of the energy of electromagnetic radiation, sound, streams of particles, etc., into other forms of energy on passing through a medium. A beam of light, for instance, passing through a medium, may lose intensity because of two effects: scattering of light out of the beam, and absorption of photons by atoms or molecules in the medium. When a photon is absorbed, there is a transition to an excited state.


Chemical Engineering
  • A mass transfer process in which one or more gases in a gaseous mixture is transferred into a liquid solvent or a solid. It is the most common form of separation of low molecular weight materials. Absorption is often used to remove gases from gas streams that may be harmful downstream or when released from the process. The absorption factor is used to determine the ease with which a component will absorb into the liquid phase and is based on liquid and vapour flow rates as well as the vapour liquid equilibrium for the component. For example, ammonia can be absorbed from a gas stream using water as the scrubbing liquid. Compare adsorption.


Electronics and Electrical Engineering
  • 1. Attenuation of a radiowave due to dissipation of its energy, as by the production of heat.

    2. Attenuation of a beam of light by a crystal due to localized vibrational modes in the crystal resulting from the presence of impurity atoms. This gives rise to characteristic sharp troughs in the transmission or reflection spectra and can be used to analyse the material. Absorption can also occur due to photon-induced electron transitions between different energy bands in a semiconductor and can be used to determine the energy gap.


Biology
  • The movement of fluid or a dissolved substance across a plasma membrane. In many animals, for example, soluble food material is absorbed into cells lining the alimentary canal and thence into the blood. In plants, water and mineral salts are absorbed from the soil by the roots. See osmosis; transport protein.


Logic
  • 1. A classically valid inference rule by which the antecedent of a true conditional may be conjoined to the consequent. Where and are conditional and conjunction connectives, respectively, the rule of absorption can be represented as the rule:

    φψφ(φψ)

    i.e., from φψ one may infer φ(φψ).

    2. A pair of rules of inference corresponding to the absorption identities that hold in Boolean lattices. These are the absorption of conjunction by disjunction, represented by the equivalence:

    φ(φψ)¯φ

    i.e., φ(φψ) is logically equivalent to φ itself. Dually, the absorption of disjunction by conjunction can be represented as the rule:

    φ(φψ)¯φ

    3. Another name for contraction in sense 2.


Geology and Earth Sciences
  • 1. A chemical or physical process in which an amount of one substance enters a solid or liquid bulk phase of another; the substance absorbed is taken up by the volume of the absorbing substance. Compare adsorption; see also sorption.

    2. The amount of seismic energy lost during transmission, by conversion to heat. The absorption coefficient is the fractional loss of energy over a distance of one wavelength; hence higher-frequency signals are attenuated more readily than those of lower frequencies over the same path. Typical values for rocks range from 0.25 to 0.75 dB per wavelength.


Economics
  • 1. In the national accounts, the total of expenditure on real goods and services, by consumers, investors, and the government. Absorption is the use of output: it excludes exports and includes imports. This is contrasted with production, which includes exports and excludes imports. The absorption approach to devaluation looks at its effects on various forms of expenditure, and points out that devaluation can only improve the balance of payments on current account if production increases relative to absorption.

    2. In industrial organization, a merger in which the acquired company transfers all its assets and liabilities to the acquiring company in exchange for its securities and cash.


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