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

<< < D l dar dat de deb dec dec dec def def dei dem den dep des deu dew dic dif dif dil dip dir dis dis dis dis diu dom Dor dou dri Dum dus dyn dyn > >>

Number of Results: 706
dipole
  دوقطبه   
doqotbé (#)

Fr.: dipole   

1) A combination of two electrically or magnetically charged particles of opposite signs, which are separated by a very small distance.
2) Chemistry: A molecule containing both positively and negatively charged groups.

di- "two, twice, double," + → pole.

dipole anisotropy
  ناهمسانگردی ِ دوقطبه   
nâhamsângardi-ye doqotbé

Fr.: anisotropie dipolaire   

A form of anistropy in the temperature of the → cosmic microwave background radiation, appearing as one hot pole and one cold pole, caused by our motion with respect to the cosmic background radiation. The temperature variations, amounting to 1 part in 1000, yield a velocity of about 600 km/sec for our Galaxy with respect to the background. → cosmic microwave background anisotropy.

dipole; → anisotropy.

dipole antenna
  آنتن ِ دوقطبه   
ânten-e doqotbé (#)

Fr.: antenne dipôle   

One of the simplest kinds of antenna which is connected at the center to a radio-frequency feed line for transmitting or receiving radio frequency energy. It differs from the dish antenna in that it consists of many separate antennas that collect energy by feeding all their weak individual signals into one common receiving set.

dipole; → antenna.

dipole moment
  گشتاور ِ دوقطبه   
gaštâvar-e doqotbé (#)

Fr.: moment dipolaire   

1) The product of the strength of either of the charges in an → electric dipole and the distance separating the two charges. It is expressed in → coulomb meters. Dipole moment is a → vector quantity. Its direction is defined as toward the positive charge. In chemistry dipole moment is a quantitative measure of polarity in a molecule; the unit is the → debye.
2) The product of the strength of either of the poles in a → magnetic dipole and the distance separating the two poles. Dipole moment is a vector quantity. Its direction is defined as toward the magnetic north pole.

dipole; → moment.

dipole radiation
  تابش ِ دوقطبه   
tâbeš-e doqotbé

Fr.: rayonnement dipolaire   

The electromagnetic radiation produced by an oscillating → electric dipole or → magnetic dipole.

dipole; → radiation.

diproton
  دیپروتون   
diproton

Fr.: diproton   

An → isotope of → helium that consists of two → protons, without any → neutrons. It is extremely → unstable.

di-; → proton.

Dirac
  دیراک   
Dirac

Fr.: Dirac   

Paul A. M. Dirac (1902-1984), English theoretical → physicist, one of the founders of → quantum mechanics and → quantum electrodynamics, Nobel Prize for Physics in 1933. → Dirac annihilation, → Dirac equation, → Dirac function, → Dirac's constant, → Fermi-Dirac statistics .

Dirac annihilation
  نابودی ِ دیراک   
nâbudi-ye Dirac

Fr.: annihilation de Dirac   

Same as → pair annihilation.

Dirac; → annihilation.

Dirac equation
  هموگش ِ دیراک   
hamugeš-e Dirâk

Fr.: équation de Dirac   

The equation that describes the behavior of an electron in a way that combines the requirements of quantum mechanics with the requirements of relativity.

Dirac; → equation.

Dirac function
  کریای ِ دیراک   
karyâ-ye Dirâk

Fr.: fonction de Dirac   

A function of x defined as being zero for all values of x other than x = x0 and having the definite integral from x = -∞ to x = +∞ equal to unity.

Dirac; → function

Dirac's constant
  پایای ِ دیراک   
pâyâ-ye Dirac

Fr.: constante de Dirac   

The → Planck's constant divided by 2π and denoted ħ, pronounced h-bar. Also called → reduced Planck's constant.

Dirac; → constant.

direct
  ۱) راست، سرراست؛ ۲) راشتیدن   
1) râst (#), sarrâst (#); 2) râštidan

Fr.: 1) direct; 2) diriger   

1a) Proceeding in a straight course or line without deviation or interruption.
1b) Math.: Varying in the same manner as another quantity, especially increasing if another quantity increases or decreasing if it decreases.
1c) Astro.: Designating west-to-east motion of a planet in the same direction as the Sun's movement against the stars.
2) To administer; manage; supervise; to serve as a director in the performance or production of.

From L. directus "straight," p.p. of dirigere "set straight," from → dis- "apart" + regere "to guide;" cognate with Pers. râst, as explained below.

Râst "right, straight" (râšt in afrâštan); Mid.Pers. râst; O.Pers. rāsta- "straight, true," rās- "to be right, straight, true," rād- "to prepare;" Av. rāz- "to direct, put in line, set," razišta- "straightest, most correct," erezu- "correct, straight," rāzayeiti "directs," razan- "order;" Skt. raj- "to direct, stretch," rjuyant- "walking straight;" Gk. orektos "stretched out;" L. regere "to lead straight, guide, rule," p.p. rectus "right, straight;" Ger. recht; E. right; PIE base *reg- "right, just; to move in a straight line."
Sarrâst, from sar here an intensive element meaning "side," originally "head" (Mid.Pers. sar; Av. sarah- "head;" Skt. siras- "head;" Gk. kara "head," keras "horn;" Mod.Pers. sarun "horn;" L. cerebrum "brain;" PIE *ker- "head, horn") + râst, as above.
Râštidan, infinitive from râšt, variant râst "direct."

direct correlation
  هم‌باز‌آنش ِ سرراست   
hambâzâneš-e sarrâst

Fr.: corrélation directe   

A correlation between two variables such that as one variable becomes large, the other also becomes large, and vice versa. The correlation coefficient is between 0 and +1. Also called positive correlation.

direct; → correlation.

direct current (DC)
  جریان ِ سرراست   
jarayân-e sarrâst

Fr.: courant continu   

An → electric current which flows in one direction only and which is substantially constant in magnitude. Virtually all electronic and computer hardware needs direct current to function. → Alternating current can be converted to direct current by means of a power supply consisting of a → transformer.

direct; → current.

direct motion
  جنبش ِ فرارو، ~ سرراست   
jonb eš-e farârow, ~ sarrâst

Fr.: mouvement direct   

The motion of a solar system body from West to East across the sky against the background stars. It is the "normal" direction of motion within the solar system. For rotating or orbiting solar system objects it is anti-clockwise as seen from above the solar system in the direction of the North Pole. The same as → prograde motion. See also → retrograde motion.

direct; → motion.

directed edge
  لبه‌ی ِ سودار   
labe-ye sudâr

Fr.: graphe orienté   

In → graph theory, an edge where endpoints are distinguished; one is the head and the other is the tail. A directed edge is specified as an ordered pair of → vertices, u, v and is denoted by (u, v) or uv.

directed; → edge.

directed graph
  نگاره‌ی ِ سودار   
negâre-ye sudâr

Fr.: graphe orienté   

In → graph theory, a graph with → directed edges. Also calle → digraph.

directed; → graph.

directed path
  په ِ سودار   
pah-e sudâr

Fr.: chemin orienté   

In a → directed graph, a path in which all → edges are oriented in the same direction.

directed; → edge.

direction
  راستا، سو؛ ۲) راشتاری   
1) râstâ, su (#); 2) râštâri

Fr.: direction   

1) A position to which motion or another position is referred.
2) The act or an instance of directing.

M.E. direccioun, from M.Fr., from L. direction-, stem of directio "arranging in line, straightening," → direct.

1) Râstâ, from directdirect + dimension suffix; su, from Mid.Pers. sôk "side."
2) Râštâri, noun from râštârdirector + suffix -i.

direction angle
  زاویه‌ی ِ راستا   
zâviye-ye râstâ

Fr.: angle de direction   

An angle made by a given vector and a coordinate axis.
The angle between the North and a chosen direction.

direct; → angle.

<< < D l dar dat de deb dec dec dec def def dei dem den dep des deu dew dic dif dif dil dip dir dis dis dis dis diu dom Dor dou dri Dum dus dyn dyn > >>