An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

   Homepage   
   


A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Number of Results: 5 Search : entropy
Boltzmann's entropy formula
  دیسول ِ درگاشت ِ بولتسمن   
disul-e dargâšt-e Boltzmann

Fr.: formule d'entropie de Boltzmann   

In → statistical thermodynamics, a probability equation relating the → entropy S of an → ideal gas to the quantity Ω, which is the number of → microstates corresponding to a given → macrostate: S = k. ln Ω. Same as → Boltzmann's relation.

Boltzmann's constant; → entropy; → formula.

entropy
  درگاشت   
dargâšt (#)

Fr.: entropie   

1) A measure of the energy that is not available for work during a → thermodynamic process. It is defined by dS = dQ/T, where dS is the differential change in entropy, dQ is the differential amount of heat introduced to the system in a → reversible process, and T the → absolute temperature of the system. Entropy remains constant during → reversible processes and increases during → irreversible processes without ever decreasing. According to the → second law of thermodynamics, an → isolated system evolves toward a state of maximum entropy. See also → Maxwell's demon.
2) Statistical physics: A measure of → disorder of the configuration of → microstates which make up a → macrostate. → Boltzmann's relation, → Boltzmann's entropy formula. Highly disordered systems have a large entropy; highly ordered systems have low entropy.
3) Math.: A measure of information content. → information entropy.

From Ger. Entropie, coined 1865 by physicist Rudolf Clausius (1822-1888) from Gk. entropia "a turning toward," from en- "in" + trope "a turning, change," related to tropos "a turn, way, manner," from tropein "to turn," from PIE base *trep- "to turn" (cf. L. trepit "he turns").

Dargâšt, from dar "in" + gâšt present stem of gâštan "to cause to revolve, to turn," transitive of gaštan, variant gardidan "to turn, to change" (Mid.Pers. vartitan; Av. varət- "to turn, revolve;" cf. Skt. vartati; L. vertere; O.H.G. werden "to become;" PIE base *wer- "to turn, bend").

information entropy
  درگاشت ِ ازدایش   
dargâšt-e azdâyeš

Fr.: entropie de l'information   

The measure of information, which is usually expressed by the average number of bits needed for storage or communication. In other words, the degree to which the values of a → random variable X are dispersed. If the → probability density function of X is P(x), the entropy is defined by: H(X) = -Σ P(x) log P(x). Also called → Shannon entropy.

information; → entropy.

maximum entropy method (MEM)
  روش ِ درگاشت ِ بیشینه   
raveš-e dargâšt-e bišiné

Fr.: méthode d'entropie maximum   

A deconvolution algorithm which functions by minimizing a smoothness function in an image. The MEM seeks to extract as much information from a measurement as is justified by the data's signal-to-noise ratio.

maximum; → entropy; → method.

Shannon entropy
  درگاشت ِ شانون   
dargâšt-e Shannon

Fr.: entropie de Shannon   

information entropy.

Claude Elwood Shannon (1916-2001), an American mathematician and pioneer of → information theory; → entropy.