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convection zone zonâr-e hambaz Fr.: zone de convection Same as → convective zone. |
conversion hâgard Fr.: conversion The act or process of converting; state of being converted. → convert. Verbal noun of → convert. Hâgard, from hâ- prefix denoting "reversal; to," sometimes creating nuance [Dehxodâ], + gard present stem of gardidan, gaštan "to change; to turn;" Mid.Pers. vartitan; Av. varət- "to turn, revolve;" cf. Skt. vrt- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wer- "to turn, bend." |
conversion factor karvand-e hâgard Fr.: facteur de conversion 1) A numerical factor that, by multiplication or division, translates one
unit or value into another. → conversion; → factor. |
convocation hamvac Fr.: convocation The act of convoking. The state of being convoked. Verbal noun of → convoke. |
convolution hamâgiš Fr.: convolution 1) A mathematical combination of two functions which involves multiplying
the value of one function at a given point with the value of another
function, the weighting function, for a displacement from that point
and then integrating over all such displacements. The process is
repeated for every point of the function. Convolution expresses how the shape of
a function is altered by the other. In mathematical terms, the convolution of two functions
f(x) and g(x) is defined by:
f*g = ∫f(u)g(x - u) du, integral from -∞ to +∞. Verbal noun of → convolve. |
convolution theorem farbin-e hamâgiš Fr.: théorème de convolution A theorem stating that the → Fourier transform of the convolution of f(x) and g(x) is equal to the product of the Fourier transform of f(x) and g(x): F{f*g} = F{f}.F{g}. → convolution; → theorem. |
coordination hamârâyeš Fr.: coordination The act or state of coordinating or of being coordinated. Verbal noun of → coordinate. |
coordination compound hamnât-e hamârâyeš Fr.: composé de coordination A chemical compound in which a group of atoms or ions are attached by a coordination bond to a usually metallic central atom or ion. → coordination; → compound. |
coordination lattice jâre-ye hamârâyeš Fr.: réseau de coordination Crystallography: The crystal structure of a → coordination compound. → coordination; → lattice. |
coordination number šomêr-e hamârâyeš Fr.: nombre de coordination 1) Crystallography: The
number of nearest neighbors of an atom or ion in a → crystal lattice.
A large coordination number indicates that the structure is more closely packed. → coordination; → number. |
Copenhagen Interpretation âzand-e Kopenhâg Fr.: interprétation de Copenhague A general heading which covers a wide variety of complex views on → quantum theory. As the first and the founding interpretation of the → quantum mechanics, it was developed in the late 1920's mainly by the Danish physicist Niels Bohr, but also Werner Heisenberg, Max Born and other physicists who made important contributions to the overall understanding of this field. Bohr expressed himself on the subject at various meetings and later published several articles and comments, but he never wrote a systematic and complete version of his views. There is not a unique Copenhagen Interpretation but various more or less complete versions, the common denominator of which is mainly the work of Bohr. Among those opposed to the Copenhagen Interpretation have been Albert Einstein, Erwin Schrödinger, Louis de Broglie, Max Planck, David Bohm, Alfred Landé, Karl Popper, and Bertrand Russell. The Copenhagen Interpretation recognizes that the deterministic picture of the universe that works so well at the macroscopic level does not work for the world at the quantum level. The universe at the quantum level is predictable only in a statistical sense. This implies that we can never really know the nature of quantum phenomena. The four cornerstones of the Copenhagen Interpretation are: → wave-particle duality, the probability → wave function, the → uncertainty principle, and the significance of the → observer. The observer is of the utmost importance because he causes the reality to unfold in the way it does. The key feature of the Copenhagen Interpretation is a concept known as the → collapse of the wave function, for which there is no known physical explanation; see also → Schrodinger's cat. Copenhagen, from Dan. København "merchant's port," from køber "merchant" ("buyer") + havn "port," from the fact that the originator and chief interpreter of this school was Niels Bohr whose headquarters was in Copenhagen; → interpretation. |
core mass function (CMF) karyâ-ye jerm-e maqzé Fr.: fonction de masse des cœurs The mass distribution of → pre-stellar cores in → star-forming regions. The CMF is usually represented by dN/dM = M^{α}, where dM is the mass interval, dN the number of cores in that interval, and α takes different values in different mass ranges. In the case of → low-mass stars, it is found that the CMF resembles the → Salpeter function, although deriving the masses and radii of pre-stellar cores is not straightforward. The observational similarity between the CMF and the → initial mass function (IMF) was first put forth by Motte et al. (1988, A&A, 336, 150), and since then many other samples of dense cores have been presented in this context. For example, Nutter & Ward-Thompson (2007, MNRAS 374, 1413), using SCUBA archive data of the Orion star-forming regions, showed that the CMF can be fitted to a three-part → power law consistent with the form of the stellar IMF. Recent results, obtained using observations by the → Herschel Satellite, confirm the similarity between the CMF and IMF with better statistics (Könyves et al. 2010, A&A, 518, L106; André et al. 2010, A&A, 518, L102). Moreover, these works show that the CMF has a → lognormal distribution (i.e. dN/dlog M follows a → Gaussian form against log M), as is the case for the IMF at low masses (below about 1 solar mass). |
Coriolis acceleration šetâb-e Coriolis (#) Fr.: accélération de Coriolis The apparent acceleration corresponding to the → Coriolis force. It is the acceleration which, when added to the acceleration of an object relative to a rotating → reference frame and to its → centrifugal acceleration, gives the acceleration of the object relative to a fixed reference frame. Coriolis acceleration equals 2ω x v, where ω is the → angular velocity of the rotating reference frame and v is the radial velocity of a particle relative to the center of the rotating reference frame. → Coriolis effect; → force. |
coronal condensation cagâleš-e tâji Fr.: condensation coronale A part of the → solar corona where the gas density and the temperature are higher than in its vicinity. The coronal condensations are visible on the solar limb, above → sunspot groups. Images in X-rays and those supplied by → coronagraphs in white light reveal that such condensations consist of structures in the form of nodes, underlining the corona magnetic field (M.S.: SDE). → coronal; → condensation. |
coronal mass ejection (CME) ešâneš-e jerm az hurtâj Fr.: éjection de masse coronale A huge eruption of material from regions of the solar corona in which the magnetic field is closed, but which suffer an extremely energetic disruption. Over the course of several hours up to 10,000 billion kg of this material is ejected into → interplanetary space with a a speed of as high as 3000 km/s. CMEs are most spectacularly observed by a white light coronagraph located outside Earth's atmosphere. Such observations from Skylab in the early 1970's were the first to reveal this phenomenon. CME's disrupt the flow of the → solar wind and can produce intense electromagnetic disturbances that can severely damage satellites and disrupt power grids on Earth. When these ejections reach the Earth, they give rise to → geomagnetic storms. The frequency varies with the → solar cycle; during solar minimum they come at a rate of about one per week, and during maximum there is an average of about two or three per day. See also → interplanetary coronal mass ejections (ICME). |
corotating interaction region (CIR) nâhiye-ye andaržireš-e hamcarxandé Fr.: région d'interaction en corotation A spiral-shaped density enhancement formed around a star when fast stellar winds collide with slower material. This large-scale wind structure can extend from the stellar surface to possibly several tens of stellar radii. The CIRs can be produced by intensity irregularities at the stellar surface, such as dark and bright spots, magnetic loops and fields, or non-radial pulsations. The surface intensity variations alter the radiative wind acceleration locally, which creates streams of faster and slower wind material. CIRs are responsible for the → discrete absorption components seen in some ultraviolet → resonance lines of → hot stars (S. R. Cranmer & S. P. Owocki, 1996, ApJ 462, 469). → corotate; → interaction; → region. |
corotation hamcarxeš Fr.: corotation The act of corotating. Verbal noun of → corotate. |
corotation radius šoâ'-e ham-carxeš Fr.: rayon de corotation 1) In the → X-wind model of → accretion,
the distance from the star where the → centrifugal force
on a particle corotating with the star balances the
→ gravitational attraction; in other words, where the
→ accretion disk rotates at the same
→ angular velocity as the star. → corotation; → radius. |
corotation resonance bâzâvâyi-ye ham-carxeš Fr.: résonance de corotation That condition of a → galactic disk at an orbital radius in which the → angular velocity of the disk equals the → pattern speed. It is significant that the spiral wave pattern rotates as a rigid body (Ω_{P} = const), whereas the galactic disk rotates differentially (Ω is a function of galactocentric distance r). The distance r_{C} at which the two angular velocities coincide (Ω(r_{C}) = Ω_{P}) is referred to as the → corotation radius. The corotation resonance and its position within the galaxy is one of the fundamental properties of a spiral galaxy. → corotation; → resonance. |
corpuscular radiation tâbeš-e karpuli Fr.: rayonnement corpusculaire A stream of atomic or subatomic particles. |
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