Capable of returning to an original condition. → reversible process.
farâravand-e vâgaštpazir (#)
Fr.: processus réversible
Any physical process which can be performed in the reverse direction, the whole series of changes constituting the process being exactly reversed. → irreversible process.
lâye-ye vâgardân (#)
Fr.: couche d'inversion
A layer of relatively cool gas forming the lower part of the Sun's chromosphere, just above the photosphere, that gives rise to absorption lines in the Sun's spectrum.
1) bâzdâ; 2) bâzdâ kardan
Fr.: 1) revue; 2) faire une revue
1a) A critical article or report.
M.E., from O.Fr. reveue "a reviewing, review," from feminine p.p. of revoir "to see again, reexamine," from O.Fr. reveoir, from → re- + veoir, veeir "to see."
Bâzdâ, from bâz-, → re-, + dâ root of didan "to see" (Mid.Pers. ditan "to see, regard, catch sight of, contemplate, experience;" O.Pers. dī- "to see;" Av. dā(y)- "to see," didāti "sees;" cf. Skt. dhī- "to perceive, think, ponder; thought, reflection, meditation," dādhye; Gk. dedorka "have seen") + kardan "to do," → -or.
Fr.: papier de revue
A talk that deals with a subject by examining, criticizing, and summarizing the facts.
To alter something already written or printed, in order to make corrections, improve, or update (Dictionary.com).
the act or work of revising. a process of revising. a revised form or version, as of a book.
Verbal noun of → revise.
The act of revoking; annulment.
Verbal noun of → revoke.
1) To take back or withdraw; annul, cancel, or reverse; rescind or repeal.
The movement of a celestial body which is in orbit around another. It is often measured as the → orbital period.
Verbal noun of → revolve.
To move in a an orbit around another object. Compare with → rotate.
M.E. revolven, from L. revolvere "to turn, roll back," from → re- "back, again" + volvere "to roll."
Gardidan variant gaštan "to turn, to change;" gardun "wheel; chariot;" (+ → ni-) navardidan, navard- "to twist; to fold; to stroll;" Mid.Pers. wardidan, walt- "to turn; twist;" Av. varət- "to turn, revolve;" cf. Skt. vart- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wert- "to turn, bend."
adad-e Reynolds (#)
Fr.: nombre de Reynolds
A dimensionless quantity that governs the conditions for hydrodynamic stability and the occurrence of turbulence in fluids. It is defined by the ratio, R, of the inertial force (ρ u2) and the viscous force (μ u / L), i.e. R = L u ρ/μ, where L is a typical dimension of the system, u is a measure of the velocities that prevail, ρ the density, and μ the kinematic viscosity. At low Reynolds numbers the flow is steady, since the viscous forces are predominant in controlling the flow. At a critical value of R, corresponding to a critical velocity, the flow becomes turbulent.
Named after Osborne Reynolds (1842-1912), a British physicist who pioneered the study of turbulent flows; → number.
Fr.: étoile RHB
Same as → red horizontal branch star.
The second largest satellite of Saturn, also known as Saturn V. It has a diameter of 1530 km and orbits Saturn at a mean distance of 527,040 km in 4.518 days. Rhea is composed primarily of water ice with rock making up less than 1/3 of its mass. It was discovered by Cassini in 1672.
In Gk. mythology Rhea was the sister and wife of Cronus (Saturn) and the mother of Demeter, Hades (Pluto), Hera, Hestia, Poseidon (Neptune), and Zeus (Jupiter).
A metallic chemical element; symbol Re. Atomic number 75; atomic weight 186.207; melting point about 3,180°C; boiling point about 5,625°C. Rhenium is a very dense, high-melting, silver-white metal; specific gravity 21.02 at 20°C. Of the elements, only carbon and tungsten have higher melting points and only iridium, osmium, and platinum are more dense. It was discovered by x-ray spectroscopy in 1925 by the German chemists, Walter Noddack, Ida Tacke and Otto Berg.
The name derives from L. rhenus for "the Rhine river in Germany".
ravâné šenâsi (#)
A branch of physics dealing with the way matter flows and deforms.
Ravâné, from ravân "flowing, running," pr.p. of raftan "to go, walk; to flow;" (Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack") + šenâsi, → -logy.
Relating to a constraint or system that contains time explicitly. For example, a pendulum with an extensible string of length l rheonomous, the condition of constraint is: x2 + y2 = l2(t), where l(t) is the length of the string at time t.
Fr.: Rho Cassiopée
A → yellow hypergiant in the constellation Cassiopeia, classified as F8-G2 Ia0pe. Rho Cas is about 11,650 light-years away from Earth, yet can still be seen by the naked eye, as it is 550,000 times as luminous as the Sun. It is in fact one of the most luminous stars in our Galaxy. ρ Cas is also one of the only seven currently known yellow hypergiants in the Milky Way. It is variable and fluctuates around magnitude 5 but dimmed to 6th magnitude on 1946. Its last eruption happened in 2000-2001, during which the star ejected about 10 percent of a solar mass, dimmed by more than a full magnitude, and changed its spectral type from late F to early M. During this outburst, the star surface cooled from 7,000 to 4,000 K.
Rho Ophiuchi Cloud
abr-e rho Mâr-afsâ
Fr.: Nuage de rho Ophiuchi
A complex region of molecular and dust clouds containing emission and reflection nebulae near the star ρ Oph in the constellation → Ophiuchus. It is one of the closest star forming regions, some 400 light-years distant. Recent studies using the latest X-ray and infrared observations reveal more than 300 young stellar objects within the large central cloud. Their median age is only 300,000 years.
A metallic chemical element; symbol Rh. Atomic number 45; atomic weight 102.9055; melting point about 1,966°C; boiling point 3,727±100°C; specific gravity 12.41 at 20°C. Rhodium was discovered in 1803 by the English chemist and physicist William Hyde Wollaston during experiments on crude platinum ore.
The name derives from Gk. rhodon "rose" because of the "rose color of dilute solutions of its salts."