Fr.: principe d'Alembert-Lagrange
Fr.: faire une déflagration, s'enflammer
To burn suddenly and violently with great heat and intense light. → deflagration.
From L. deflagratus, p.p. of deflagrare "to burn down," from → de- + flag(rare) "to blaze, glow, burn" (L. fulgur "lightning;" PIE *bhleg- "to shine;" cf. Gk. phlegein "to burn, scorch," Skt. bhárgas- "radiance, lustre, splendour," O.E. blæc "black") + -atus "-ate"
Taškaftidan, from taš "fire," variant of âtaš→ fire + kaftidan "to explode," → explode.
A rapid → chemical reaction in which the → output of → heat is enough to enable the reaction to proceed and be accelerated without input of heat from another source. The effect of a true deflagration under confinement is an → explosion. See also: → detonation; → explosion.
Verbal noun of → deflagrate.
inner Lagrangian point
noqte-ye Lagrange-e daruni (#)
Fr.: point de Lagrange interne
One of the five → Lagrangian points, denoted L1, which lies between the two bodies on the line passing through their center of mass. In a → close binary star system mass transfer occurs through this point.
1) lek; 2) lekidan
Fr.: 1) retard, décalage; 2) rester en arrière traîner
1a) A lagging or falling behind; retardation.
Possibly from Scandinavian; cf. Norwegian lagga "to go slowly."
Lek, from lek lek kardan "to walk slowly, to lag behind."
1) A body of seawater that is almost completely cut off from the ocean by a barrier beach.
Lagoon, from Fr. lagune, from It. laguna "pond, lake," from L. lacuna "pond, hole," from lacus "pond;" → nebula.
Mordâb "lagoon," literally "dead water," from mord, mordé "dead"
+ âb "water."
Lagoon Nebula (M8, NGC 6523)
miq-e mordâb (#)
Fr.: nébuleuse de la lagune
A giant → H II region lying in the direction of → Sagittarius about 5,000 → light-years away. It represents a giant cloud of interstellar matter which is currently undergoing star formation, and has already formed a considerable cluster of young stars (NGC 6530).
Fr.: équation de Lagrange
A set of second order → differential equations for a system of particles which relate the kinetic energy of the system to the → generalized coordinates, the generalized forces, and the time. If the motion of a → holonomic system is described by the generalized coordinates q1, q2, ..., qn and the → generalized velocities q.1, q.2, ..., q.n, the equations of the motion are of the form: d/dt (∂T/∂q.i) - ∂T/∂q.i = Qi (i = 1, 2, ..., n), where T is the kinetic energy of the system and Qi the generalized force.
1) Of or relating to Joseph-Louis Lagrange (1736-1813), see below.
After the French/Italian mathematician Joseph-Louis Lagrange (1736-1813), who was the creator of the → calculus of variations (at the age of nineteen). He made also great advances in the treatment of → differential equations and applied his mathematical techniques to problems of → mechanics, especially those arising in astronomy.
Fr.: densité lagrangienne
A quantity, denoted Ld, describing a continuous system in the
→ Lagrangian formalism, and defined as the
→ Lagrangian per unit volume.
It is related to the Lagrangian L by:
Fr.: dynamique lagrangienne
A reformulation of → Newtonian mechanics in which dynamical properties of the system are described in terms of generalized variables. In this approach the → generalized coordinates and → generalized velocities are treated as independent variables. Indeed applying Newton's laws to complicated problems can become a difficult task, especially if a description of the motion is needed for systems that either move in a complicated manner, or other coordinates than → Cartesian coordinates are used, or even for systems that involve several objects. Lagrangian dynamics encompasses Newton dynamics, and moreover leads to the concept of the → Hamiltonian of the system and a process by means of which it can be calculated. The Hamiltonian is a cornerstone in the field of → quantum mechanics.
Fr.: formalisme lagrangien
A reformulation of classical mechanics that describes the evolution of a physical system using → variational principle The formalism does not require the concept of force, which is replaced by the → Lagrangian function. The formalism makes the description of systems more simpler. Moreover, the passage from classical description to quantum description becomes natural. Same as → Lagrangian dynamics.
karyâ-ye lâgrânž (#)
Fr.: Lagrangien, fonction de Lagrange
A physical quantity (denoted L), defined as the difference between the → kinetic energy (T) and the → potential energy (V) of a system: L = T - V. It is a function of → generalized coordinates, → generalized velocities, and time. Same as → Lagrangian, → kinetic potential.
Fr.: méthode lagrangienne
Fluid mechanics: An approach in which a single fluid particle (→ Lagrangian particle) is followed during its motion. The physical properties of the particle, such as velocity, acceleration, and density are described at each point and at each instant. Compare with → Eulerian method.
Fr.: multiplicateur de Lagrange
Math.: A constant that appears in the process for obtaining extrema of functions of several variables. Suppose that the function f(x,y) has to be maximized by choice of x and y subject to the constraint that g(x,y)≤ k. The solution can be found by constructing the → Lagrangian function L(x,y,λ) = f(x,y) + λ[k - g(x,y)], where λ is the Lagrangian multiplier.
Fr.: particule lagrangienne
Fluid mechanics: In the → Lagrangian method, a particle that moves as though it is an element of fluid. The particle concept is an approach to solving complicated fluid dynamics problems by tracking a large number of particles representing the fluid. The particle may be thought of as the location of the center of mass of the fluid element with one or more property values.
noqtehâ-ye Lagrange (#)
Fr.: points de Lagrange
On of the five locations in space where the → centrifugal force and the → gravitational force of two bodies (m orbiting M) neutralize each other. A third, less massive body, located at any one of these points, will be held in equilibrium with respect to the other two. Three of the points, L1, L2, and L3, lie on a line joining the centers of M and m. L1 lies between M and m, near to m, L2 lies beyond m, and L3 on the other side of M beyond the orbit. The other two points, L4 and L5, which are the most stable, lie on either side of this line, in the orbit of m around M, each of them making an equilateral triangle with M and m. L4 lies in the m's orbit approximately 60° ahead of it, while L5 lies in the m's orbit approximately 60° behind m. See also → Trojan asteroid; → Roche lobe; → equipotential surface; → horseshoe orbit.
lek-e forušod-e mâng
Fr.: retard du coucher de la lune
Fr.: différence de phase
1) General: Same as → phase difference.
→ phase; lag, possibly from a Scandinavian source; cf. Norw. lagga "go slowly."
A bright cloud-like feature that appears in the vicinity of a sunspot. Plages represent regions of higher temperature and density within the chromosphere. They are particularly visible when photographed through filters passing the spectral light of hydrogen or calcium.
From Fr., from It. piaggia, from L.L. plagia "shore;" noun use of the feminine of plagius "horizontal;" frpm Gk. plagios "slanting, sideways" from plag(os) "side" + -ios adj. suffix.
Plâž, loan from Fr., as above.