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  2. Coefficient of variation - Wikipedia

    en.wikipedia.org/wiki/Coefficient_of_variation

    This follows from the fact that the variance and mean are independent of the ordering of x. Scale invariance: c v (x) = c v (αx) where α is a real number. [22] Population independence – If {x,x} is the list x appended to itself, then c v ({x,x}) = c v (x). This follows from the fact that the variance and mean both obey this principle.

  3. Angular diameter - Wikipedia

    en.wikipedia.org/wiki/Angular_diameter

    Thus, the angular diameter of Earth's orbit around the Sun as viewed from a distance of 1 pc is 2″, as 1 AU is the mean radius of Earth's orbit. The angular diameter of the Sun, from a distance of one light-year, is 0.03″, and that of Earth 0.0003″. The angular diameter 0.03″ of the Sun given above is approximately the same as that of a ...

  4. Equation of time - Wikipedia

    en.wikipedia.org/wiki/Equation_of_time

    The correct branch of the multiple valued function arctan x to use is the one that makes ν a continuous function of E(M) starting from ν E=0 = 0. Thus for 0 ≤ E < π use arctan x = arctan x, and for π < E ≤ 2π use arctan x = arctan x + π. At the specific value E = π for which the argument of tan is infinite, use ν = E.

  5. Dynamic stall on helicopter rotors - Wikipedia

    en.wikipedia.org/wiki/Dynamic_stall_on...

    Stage 2: flow separation and the formation of a vortex disturbance is cast-off from the leading edge region of the airfoil. This vortex, called leading edge vortex ( LEV ) or dynamic stall vortex ( DSV ), provides an additional lift for the airfoil so long as it stays over the upper surface, and also noteworthy increases in nose-down pitching ...

  6. Minute and second of arc - Wikipedia

    en.wikipedia.org/wiki/Minute_and_second_of_arc

    A second of arc, arcsecond (abbreviated as arcsec), or arc second, denoted by the symbol ″, [2] is a unit of angular measurement equal to ⁠ 1 / 60 ⁠ of a minute of arc, ⁠ 1 / 3600 ⁠ of a degree, [1] ⁠ 1 / 1 296 000 ⁠ of a turn, and ⁠ π / 648 000 ⁠ (about ⁠ 1 / 206 264.8 ⁠) of a radian.

  7. Milliradian - Wikipedia

    en.wikipedia.org/wiki/Milliradian

    A milliradian (SI-symbol mrad, sometimes also abbreviated mil) is an SI derived unit for angular measurement which is defined as a thousandth of a radian (0.001 radian). ). Milliradians are used in adjustment of firearm sights by adjusting the angle of the sight compared to the barrel (up, down, left, or

  8. Normal distribution - Wikipedia

    en.wikipedia.org/wiki/Normal_distribution

    If the mean =, the first factor is 1, and the Fourier transform is, apart from a constant factor, a normal density on the frequency domain, with mean 0 and variance ⁠ / ⁠. In particular, the standard normal distribution ⁠ φ {\displaystyle \varphi } ⁠ is an eigenfunction of the Fourier transform.

  9. Quartz crystal microbalance - Wikipedia

    en.wikipedia.org/wiki/Quartz_crystal_microbalance

    Here Z F is the acoustic impedance of the film (Z F = ρ F c F = (ρ F G f) 1/2)= (ρ F /J f) 1/2), k F is the wave vector and d F is the film thickness. J f is the film's viscoelastic compliance, ρ F is the density. The poles of the tangent (k F d F = π/2) define the film resonances. [55] [56] At the film resonance, one has d F = λ/4. The ...