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

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.

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

→ linear; → regression.

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

→ linear; → size.

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.

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.

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.

A process of reduction to linear form by appropriate change of variables or by approximation.

Verbal noun of → linearize.

To make linear; give linear form to.

→ linear + → -ize.

A differential equation that has been derived from an original nonlinear equation.

Linearized, p.p. of → linearize; → differential; → equation.

In a manner characterized by first-degree algebraic terms.

Adverb of → linear.

A set of objects x₁, x₂, ..., x_n (→ vectors, → matrices, → polynomials, etc.) on a given set if there is a linear combination of them: a₁x₁ + a₂x₂ + ... + a_nx_n, which is zero, but at least one of the coefficients is non-zero. For example the binomials (2x + y) and (6x + 3y) are linearly dependent, since 3(2x + y) - (6x + 3y) = 0.

→ linearly; → dependent.

1) A set of objects x₁, x₂, ..., x_n (→ vectors, → matrices, → polynomials, etc.) if it si not → linearly dependent.
2) Of two particular solutions (y₁, y₂) of a → homogeneous linear differential equation of the second order (y^'' + a₁ y^' + a₂y = 0) on an interval [a, b], if their ratio in this interval is not a constant: y₁/y₂≠ constant.

→ linearly; → independent.

Light exhibiting → linear polarization.

→ linearly; → polarized; → light.

Close; to a point or place not far away.

O.E. near "closer, nearer," comparative of neah, neh "nigh."

Nazdik, from Mid.Pers. nazdik "near," from nazd "close" (Mid.Pers. nazd, nazdik "near," nazdist "first;" O.Pers. ašna- "close;" Av. nazdišta- "nearest, next," nazdyo "nearer to," nas- "to come near, approach, reach;" cf. Skt. nédīyas- "closer, very close," nas- "to approach, to reach") + -ik, → -ic.

The longest wavelengths of the ultraviolet region, which are adjacent to the visible, from 200 to 350 nm.

→ near; → ultraviolet.

An → asteroid whose orbit lies partly between 0.983 and 1.3 → astronomical units from the Sun, so that it passes close to the Earth. Currently thousands of near-Earth asteroids are known, ranging in size up to about 30 km. Among them, there are between 500 and 1,000 such asteroids larger than one km in diameter. They are divided into three subclasses: → Amor asteroids, → Apollo asteroids, and → Aten asteroids. See also → near-Earth object.

→ near; → earth; → asteroid.

An → asteroid, → comet, or large → meteoroid whose orbit brings it exceptionally close to the Earth, and which may therefore pose a collision danger. Most such objects are in orbits around the Sun with → perihelion distance less than 1.3 → astronomical units. See also → near-Earth asteroid.

→ near; → earth; → object.

That region of the → electromagnetic spectrum covering shorter infrared wavelengths. It contains the → infrared windows between about 0.8 and 8 → microns, but the longer wavelength limit is not well defined. See also: → infrared radiation, → mid-infrared, → far-infrared, → submillimeter radiation.

→ near; → infrared.

A → linear differential equation if Q(x)≠ 0 on interval I.

→ nonhomogeneous; → linear; → differential; → equation.

Not a linear function of the relevant variables.
Containing a variable with an exponent other than one; opposite of → linear.

→ non-; → linear.