An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 490
xatti (#)

Fr.: linéaire   

Confined to first-degree algebraic terms in the relevant variables.

Adj. of → line.

linear acceleration
  شتاب ِ خطی   
šetâb-e xatti

Fr.: accélération linéaire   

The rate of change of the → linear velocity with time. It is defined by the expression Δvt and is equal to the → first derivative of the → linear velocity.

linear; → acceleration.

linear approximation
  نزدینش ِ خطی   
nazdineš-e xatti

Fr.: approximation linéaire   

Taking the first term in the Taylor series as an approximation to a mathematical function at a given point. → first approximation.

linear; → approximation.

linear astrolabe
  اسطرلاب ِ خطی   
ostorlâb-e xatti

Fr.: astrolabe linéaire   

A version of → planispheric astrolabe in which the → celestial sphere and the various circles of altitude and declination are projected on to a line represented by a staff. The staff is equivalent to the meridian line and contains markings to indicate the centers of these circles and their intersections with the meridian. By attaching three ropes to the appropriate points on the staff to act as radii, the circles and their intersections can be reconstructed. One of the ropes was attached to a plumb line. A scale giving chord lengths in the meridian circle extended the linear astrolabe's range of applications. It was invented by the Iranian mathematician and astronomer Sharafeddin Tusi (c1135-1213), but no early example has survived. Same as → Sharafeddin's staff and Tusi's staff.

linear; → astrolabe.

linear correlation
  هم‌باز‌آنش ِ خطی   
hambâzâneš-e xatti

Fr.: corrélation linéaire   

A measure of how well data points fit a straight line. When all the points fall on the line it is called a perfect correlation. When the points are scattered all over the graph there is no correlation.

linear; → correlation.

linear diameter
  ترامون ِ خطی   
tarâmun-e xatti

Fr.: diamètre linéaire   

The real physical diameter, as opposed to angular diameter.

linear; → diameter.

linear differential equation
  هموگش ِ دگرسانه‌ای ِ خطی   
hamugeš-e degarsâne-yi-ye xatti

Fr.: équation différentielle linéaire   

An equation in which the → dependent variable y and all its differential coefficients occur only in the first degree. A linear differential equation of → order  order n has the form:
fn(x)y(n) + fn-1(x)y(n-1) + ... + f1(x)y' + f0(x)y = Q(x),
where f0(x), f1(x), ..., fn(x) and Q(x) are each continuous functions of x defined on a common interval I and fn(x)≠ 0 in I. A linear differential equation cannot have, for example, terms such as y2 or (y')1/2. See also: → homogeneous linear differential equation; → nonhomogeneous linear differential equation.

linear; → differential; → equation.

linear electric quadrupole
  چهارقطبه‌ی ِ برقی ِ خطی   
cahârqotbe-ye barqi-ye xatti

Fr.: quadrupôle électrique linéaire   

A system of three charges +q, -2q, and +q, arranged along a line to form an axial quadrupole. The → electric potential  V due to a linear quadrupole varies as 1/r3, whereas the → electric intensity  E varies as 1/r4.

linear; → electric; → quadrupole.

linear equation
  هموگش ِ خطی   
hamugeš-e xatti

Fr.: équation linéaire   

An equation composed of first degree variables and representing a straight line.

linear; → equation.

linear function
  کریای ِ خطی   
karyâ-ye xatti

Fr.: fonction linéaire   

A function expressed by a → first degree equation that can be graphically represented in the → Cartesian coordinate plane by a → straight line.

linear; → function.

linear instability
  ناپایداری ِ خطی   
nâpâydâri-ye xatti (#)

Fr.: instabilité linéaire   

An instability that can be described (to first-order accuracy) by linear (or tangent linear) equations.

linear; → instability.

linear momentum
  جنباک ِ خطی   
jonbâak-e xatti

Fr.: quantité de mouvement linéaire   

The product of an object's → mass and → velocity. It is a → vector and points in the same direction as the velocity vector. Linear momentum is distinguished from → angular momentum. When there is no opportunity for confusion, usually the term momentum is used instead of linear momentum.

linear; → momentum.

linear perturbation theory
  نگره‌ی ِ پرتورش ِ خطی   
negare-ye partureš-e xatti

Fr.: théorie de perturbation linéaire   

Assumption that the variations in the plasma parameters, due to the presence of waves, are small (to the first order) as compared to the undisturbed parameters. This makes it possible to linearize equations by dropping out second order (and higher) nonlinear terms.

linear; → perturbation; → theory.

linear polarization
  قطبش ِ خطی   
qotbeš-e xatti (#)

Fr.: polarisation linéaire   

Of an electromagnetic radiation, a → polarization in which the electric vibrations are confined to one plane along the direction of propagation. Also called → plane polarization. See also → circular polarization.

linear; → polarization.

linear programming
  برنامه‌سازی ِ خطی   
barnâme-sâzi-ye xatti (#)

Fr.: programmation linéaire   

A procedure for finding the maximum or minimum of a → linear function where the → arguments are subject to linear → constraints. For problems involving more than two variables or problems involving a large number of constraints, solution methods used are those that are adaptable to computers. A well-known such → algorithm is the → simplex method.

linear; → programmings.

linear regression
  وایازی ِ خطی   
vâyâzi-ye xatti

Fr.: regression linéaire   

In statistics, a regression method that establishes a linear relationship between two random variables.

linear; → regression.

linear size
  اندازه‌ی ِ خطی   
andâze-ye xatti

Fr.: taille linéaire   

The real, physical size, as opposed to angular size.

linear; → size.

linear system
  راژمان ِ خطی   
râžmân-e xatti

Fr.: système linéaire   

Physics: A → dynamical system whose evolution is a linear process. If a change in any variable at some initial time produces a change in the same or some other variable at some later time, twice as large a change at the same initial time will produce twice as large a change at the same later time.

linear; → system.

linear velocity
  تندای ِ خطی   
tondâ-ye xatti

Fr.: vitesse linéaire   

The rate of change of the position of an object that is traveling along a straight path. In other words, the velocity of an object when its moving direction is not changing. For a given → angular velocity (ω), the linear velocity v of the particle is directly proportional to the distance of the particle from the center of the circular path: v = ω ×r.

linear; → velocity.


Fr.: linéarité   

The property, condition, or state of being linear.
Math.: A relationship between two variables so that when plotted on a graph they yield a straight line.

linear; → -ity.

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