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  2. Parts-per notation - Wikipedia

    en.wikipedia.org/wiki/Parts-per_notation

    In fractions like "2 nanometers per meter" (2 n m / m = 2 nano = 2×10 −9 = 2 ppb = 2 × 0.000 000 001), so the quotients are pure-number coefficients with positive values less than or equal to 1. When parts-per notations, including the percent symbol (%), are used in regular prose (as opposed to mathematical expressions), they are still pure ...

  3. Decimal - Wikipedia

    en.wikipedia.org/wiki/Decimal

    An example of a fraction that cannot be represented by a decimal expression (with a finite number of digits) is ⁠ 1 / 3 ⁠, 3 not being a power of 10. More generally, a decimal with n digits after the separator (a point or comma) represents the fraction with denominator 10 n, whose numerator is the integer obtained by removing the separator.

  4. Orders of magnitude (numbers) - Wikipedia

    en.wikipedia.org/wiki/Orders_of_magnitude_(numbers)

    1/52! chance of a specific shuffle Mathematics: The chances of shuffling a standard 52-card deck in any specific order is around 1.24 × 10 −68 (or exactly 1 ⁄ 52!) [4] Computing: The number 1.4 × 10 −45 is approximately equal to the smallest positive non-zero value that can be represented by a single-precision IEEE floating-point value.

  5. Sampling fraction - Wikipedia

    en.wikipedia.org/wiki/Sampling_fraction

    In sampling theory, the sampling fraction is the ratio of sample size to population size or, in the context of stratified sampling, the ratio of the sample size to the size of the stratum. [1] The formula for the sampling fraction is =, where n is the sample size and N is the population size. A sampling fraction value close to 1 will occur if ...

  6. Porosity - Wikipedia

    en.wikipedia.org/wiki/Porosity

    Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%.

  7. Graphene - Wikipedia

    en.wikipedia.org/wiki/Graphene

    At a wavelength of 670 nm (6.7 × 10 −7 m), measured refractive index and extinction coefficient values are 3.135 and 0.897, respectively. Thickness determination yielded 3.7 Å across a 0.5mm area, consistent with the 3.35 Å reported for layer-to-layer carbon atom distance of graphite crystals. [ 113 ]