seri-ye Bâlmer (#)
Fr.: série de Balmer
A series of hydrogen → spectral lines
(Hα, Hβ, Hγ, and others) that lies in the visible
portion of the spectrum and results when electrons from upper
→ energy levels (n > 2) undergo
→ transition to n =
Fr.: série de Brackette
A series of lines in the infrared spectrum of atomic hydrogen due to electron jumps between the fourth and higher energy levels (Br α has wavelength 4.052 μm, Br γ 2.166 μm).
Named after the American physicist Frederick Brackett (1896-1980); → series.
complex Fourier series
seri-ye Fourier-ye hamtâft
Fr.: série de Fourier complexe
The complex notation for the → Fourier series of a function f(x). Using → Euler's formulae, the function can be written in cimplex form as f(x) = Σ cn einx (summed from -∞ to ∞), where the → Fourier coefficients are cn = (1/2π)∫ f(x) e-inx dx (integral from -π to +π).
Fr.: série dominée
seri-ye karânmand (#)
Fr.: série finie
A sum a1 + a2 + a3 + · · · + aN, where the ai's are real numbers. In terms of Σ-notation, it is written as a1 + a2 + a3 + · · · + aN = Σ (n = 1 to N). See also → infinite series.
Fr.: séries Fourier
A mathematical tool used for decomposing a → periodic function
into an infinite sum of sine and cosine functions. The general form of the
Fourier series for a function f(x) with period 2π is:
Fr.: série harmonique
Overtones whose frequencies are integral multiples of the → fundamental frequency. The fundamental frequency is the first harmonic.
Fr.: série de Humphreys
A series of → spectral lines in the → infrared spectrum of → neutral hydrogen emitted by electrons in → excited states transitioning to the level described by the → principal quantum number n = 6. It begins at 12368 nm (Hu α 12.37 microns) and has been traced to 3281.4 nm (3.28 microns).
Named after Curtis J. Humphreys (1898-1986), American physicist; → series.
seri-ye bikarân (#)
Fr.: série infinie
A series with infinitely many terms, in other words a series that has no last term, such as 1 + 1/4 + 1/9 + 1/16 + · · · + 1/n2 + ... . The idea of infinite series is familiar from decimal expansions, for instance the expansion π = 3.14159265358979... can be written as π = 3 + 1/10 + 4/102 + 1/103 + 5/104 + 9/105 + 2/106 + 6/107 + 5/108 + 3/109 + 5/1010 + 8/1011 + ... , so π is an "infinite sum" of fractions. See also → finite series.
seri-ye Lyman (#)
Fr.: séries de Lyman
A series of lines in the spectrum of hydrogen, emitted when electrons jump from outer orbits to the first orbit. The Lyman series lies entirely within the ultraviolet region. The brightest lines are Lyman-alpha at 1216 Å, Lyman-beta at 1026 Å, and Lyman-gamma at 972 Å.
Fr.: série de Maclaurin
A → Taylor series that is expanded about the reference point zero.
Named after Colin Maclaurin (1698-1746), a Scottish mathematician.
multivariate time series
seri-ye zamâni-ye basvartâ
Fr.: série temporelle multivariée
A → time series consisting of two or more → univariate time series which share the same time period. As an example, if we record wind velocity and wind direction at the same instant of time, we have a multi-variate time series, specifically a bivariate one.
seri-ye Paschen (#)
Fr.: série de Paschen
The spectral series associated with the third energy level of the hydrogen atom. The series lies in the infrared, with Pα at 18,751 Å, and Paschen limit at 8204 Å.
In honor of Friedrich Paschen (1865-1947), German physicist; → series.
Fr.: série de Pfund
A series of lines in the infrared spectrum of atomic hydrogen whose representing transitions between the fifth energy level and higher levels.
After August Herman Pfund (1879-1949), an American physicist and spectroscopist; → series.
seri-ye Pikering (#)
Fr.: série de Pickering
A series of → spectral lines of → singly ionized helium, observed in very hot → O-type and → Wolf-Rayet stars associated with transitions between the → energy level with → principal quantum number n = 4 and higher levels: n = 4-5 (10124 Å), n = 4-7 (5412 Å), n = 4-9 (4541 Å), n = 4-9 (4522 Å), and n = 4-11 (4200 ˚). The 4-6 (6560 Å) and 4-8 (4859 Å) transitions were originally not included in this series because they coincided with the hydrogen → Balmer series of lines and were thus obscured.
In honor of Edward C. Pickering (1846-1919), American astronomer and physicist; → series.
seri-ye tavâni (#)
Fr.: série de puissance
A series in which the terms contain regularly increasing powers of a variable. In general, a0 + a1x + a2x2 + ... + anxn, where a0, a1, etc. are constants.
1) Math.: A sequence of numbers or mathematical expressions such as the
n-th term may be written down in general form, and any
particular term (say, the r-th) may be obtained by substituting
r for n; e.g. xn is the general term of the series
1, x, x2, x3, ..., xn.
From L. series "row, chain, series," from serere "to join, link, bind together," from PIE base *ser- "to line up, join."
Seri, loan from Fr.
Fr.: série spectrale
Spectral lines or group of lines occurring in sequence.
stationary time series
seri-ye zamâni-ye istvar
Fr.: série temporelle stationnaire
A → time series if it obeys the following criteria: 1) Constant → mean over time (t). 2) Constant → variance for all t, and 3) The → autocovariance function between Xt1 and Xt2 only depends on the interval t1 and t2.
seri-ye Taylor (#)
Fr.: série de Taylor
A series expansion of an infinitely differentiable function about a point a: Σ (1/n!) (x - a) n f n (a), where fn(a) is the n-th derivative of f at a, and the sum over n = 0 to ∞. If a = 0 the series is called a → Maclaurin series.
Named for the English mathematician Brook Taylor (1685-1731); → series.