Fr.: diagramme de phases
A graph showing the equilibrium relationships between phases (such as vapor-liquid, liquid-solid) of a chemical compound, mixture of compounds, or solution.
Fr.: différence de phase
The difference of phase (usually expressed as a time or an angle) between two periodic quantities which vary sinusoidally and have the same frequency.
Fr.: équilibre de phases
The condition of temperature and pressure under which different phases (e.g. gas, liquid, and solid) of a substance coexist.
Fr.: fonction de phase
The variation in brightness of a target as the phase angle (the angle between Sun and observer as seen from the target) varies between 0° and 180°. The directional distribution of reflected (or scattered) radiation. The phase angle is the supplement of the scattering angle (the angle between the incident ray and the emerging ray); in other words, the sum of the phase angle and the scattering angle is always 180° (Ellis et al., 2007, Planetary Ring Systems, Springer).
Fr.: différence de phase
1) General: Same as → phase difference.
→ phase; lag, possibly from a Scandinavian source; cf. Norw. lagga "go slowly."
Fr.: blocage de phase
In electronics, a technique of adjusting the phase of an oscillator signal so that it will follow the phase of a reference signal.
→ phase; lock, from O.E. loc "bolt, fastening, enclosure;" cf. O.N. lok "fastening, lock," Goth. usluks "opening," O.H.G. loh "dungeon," Ger. Loch "opening, hole," Du. luck "shutter, trapdoor."
Fâz, → phase; bast "fastening, lock," from bastan, from Mid.Pers. bastan/vastan "to bind, shut," Av./O.Pers. band- "to bind, fetter," banda- "band, tie," Skt. bandh- "to bind, tie, fasten," PIE *bhendh- "to bind," cf. Ger. binden, E. bind, → band.
degarâhangeš-e fâz (#)
Fr.: modulation de phase
Modulation in which the phase angle of a sine-wave carrier is caused to depart from the carrier angle by an amount proportional to the instantaneous magnitude of the modulating wave.
vâgardâni-ye fâz, vâruneš-e ~
Fr.: inversion de phase
An angular shift in phase by 180°.
Fr.: décalage de phase
Any change in the phase of a periodic quantity or in the phase difference between two or more periodic quantities.
Fr.: espace des phases
Of a dynamical system, a six-dimensional space consisting of the set of values that the position and velocity can take together (x, y, z, vx, vy, vz). → velocity space.
phase transfer function (PTF)
karyâ-ye tarâvaž-e fâz
Fr.: fonction de transfert de phase
A measure of the relative phase in the image as function of frequency. It is the phase component of the → optical transfer function. A relative phase change of 180°, for example, results in an image with the black and white areas reversed.
Fr.: transition de phase
The changing of a substance from one phase to another, by → freezing, → melting, → boiling, → condensation, or → sublimation. Also known as phase transformation. A well known phase transition is the transition from → water to → ice. Phase transitions are often associated with → symmetry breaking. In water there is a complete symmetry under rotations with no preferred direction. Ice has a crystal structure, in which certain orientations in space are preferred. Therefore, in transition from water to ice the continuous rotational symmetry is lost.
Fr.: vitesse de phase
The speed at which any fixed phase (individual wave) in a → wave packet travels. It is expressed as vph = ω/k, where ω is the → angular frequency and k the → wave number. See also the → group velocity.
phases of Venus
Fr.: phases de Vénus
The gradual variation of the apparent shape of → Venus between a small, full → disk and a larger → crescent. The first telescopic observation of the phases of Venus by Galileo (1610) proved the → Ptolemaic system could not be correct. The reason is that with the → geocentric system the phases of Venus would be impossible. More specifically, in that model Venus lies always between Earth and Sun. Hence its fully bright surface would always be toward the Sun; so Venus could not be seen in full phase from Earth. Only slim crescents would be possible. On the other hand, this phenomenon could not prove the → heliocentric system, because it could equally be explained with the → Tychonic model.
1) An occurrence, circumstance, or fact, in matter or spirit, which can be perceived
by human senses. → physical phenomenon.
From L.L. phænomenon, from Gk. phainomenon "that which appears or is seen," from phainesthai "to appear," passive of phainein "to bring to light; to show," from PIE base *bhhā- "to shine;" cf. Skt. bhāati "shines, glitters;" Av. bā- "to shine, appear, seem," bāmya- "light, luminous, bright," bānu- "light, ray;" Mid.Pers. bâm "beam of light, splendor," bâmik "brilliant," bâmdâd "morning, dawn."
Padidé, noun from padid "manifest, evident, conspicuous, in sight," variant padidâr, from Mid.Pers. pad didâr "visible," from pad "to, at, for, in," evolved to bé "to; for; in; on; with; by" in Mod.Pers. (O.Pers. paity; Av. paiti "to, toward, in, at;" cf. Skt. práti, Gk. poti) + did past stem of didan "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").
Pherkad (γ Ursae Minoris)
Fr.: Pherkad (γ UMi)
A blue → giant star in the constellation → Ursa Minor, also known as HR 5735, HD 137422, HIP 75097, BD+72°79, and SAO 8220. It has an → apparent visual magnitude of +3.0, → color indices of B -V = +0.09, U - B = +0.08, and a → spectral type of A2 III. Pherkad has a → luminosity of 1,100 Lsun, a radius of 15 Rsun, and a → surface temperature of 8,200 K. It lies 487 → light-years away from Earth.
From Ar. Al-Farqad (
Fr.: relation de Phillips
A correlation between the peak brightness of → Type Ia supernovae and the decline rate of their → light curve (15 days after the maximum). The decline rate is also correlated to the width of the peak brightness of the supernova. The brightest events are the broadest in time and brighter SNe Ia decline more slowly than dimmer ones. Applying the Phillips relation reduces the dispersion in the light curves of Type Ia SNe thus making them precise distance indicators which can be observed over large distances.
Named after Mark M. Phillips (1951-), American astronomer (Phillips et al. 1993, ApJ 413, L105); → relation.
filsuf (#), falsafedân (#)
A person who engages in → philosophy.
M.E., from O.E. philosophe, from L. philosophus "philosopher," from Gk. philosophos "philosopher, sage," literally "lover of wisdom," → philosophy; the agent noun ending -er appears in early 14th century from an Anglo-French or O.Fr. variant of philosophe.
Filsuf, from Ar., from Gk., as above. Falsafedân, literally "philosophy knower," with -dân present stem of dânestan "to know," → science.
To explain or argue in terms of philosophical speculations or theories.
A conceptual study that attempts to understand reality and answer fundamental questions about knowledge, existence, life, morality, and human nature. Philosophy deals with issues that generally are not subject to investigation through experimental verification. It focuses on questions which cannot be answered by means of observation alone. See also → philosophy of science.
From O.Fr. filosofie "philosophy, knowledge," from L. philosophia, from Gk. philosophia "love of wisdom," from philo- "loving" combining form of philos "dear; friend," from philein "to love," of unknown origin, + sophia "knowledge, wisdom," from sophis "wise, learned;" of unknown origin.
Falsafé, from Ar. falsafah, loan from Gk. philosophia, as above.