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  2. Energy conversion efficiency - Wikipedia

    en.wikipedia.org/wiki/Energy_conversion_efficiency

    6–40% (technology-dependent, 15–20% most often, median degradation for x-Si technologies in the 0.5–0.6%/year [20] range with the mean in the 0.8–0.9%/year range. Hetero-interface technology (HIT) and microcrystalline silicon (μc-Si) technologies, although not as plentiful, exhibit degradation around 1%/year and resemble thin-film ...

  3. Fine-structure constant - Wikipedia

    en.wikipedia.org/wiki/Fine-structure_constant

    This value for α gives µ 0 = 4π × 0.999 999 999 87 (16) × 10 −7 H⋅m −1, 0.8 times the standard uncertainty away from its old defined value, with the mean differing from the old value by only 0.13 parts per billion. Historically the value of the reciprocal of the fine-structure constant is often given.

  4. Percentage - Wikipedia

    en.wikipedia.org/wiki/Percentage

    The percent value is computed by multiplying the numeric value of the ratio by 100. For example, to find 50 apples as a percentage of 1,250 apples, one first computes the ratio ⁠ 50 / 1250 ⁠ = 0.04, and then multiplies by 100 to obtain 4%. The percent value can also be found by multiplying first instead of later, so in this example, the 50 ...

  5. Relative change - Wikipedia

    en.wikipedia.org/wiki/Relative_change

    A percentage change is a way to express a change in a variable. It represents the relative change between the old value and the new one. [6]For example, if a house is worth $100,000 today and the year after its value goes up to $110,000, the percentage change of its value can be expressed as = = %.

  6. Energy - Wikipedia

    en.wikipedia.org/wiki/Energy

    [14] [15] This law is a fundamental principle of physics. As shown rigorously by Noether's theorem, the conservation of energy is a mathematical consequence of translational symmetry of time, [17] a property of most phenomena below the cosmic scale that makes them independent of their locations on the time coordinate. Put differently, yesterday ...

  7. 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%.

  8. Luminous efficacy - Wikipedia

    en.wikipedia.org/wiki/Luminous_efficacy

    Luminous efficacy can be normalized by the maximum possible luminous efficacy to a dimensionless quantity called luminous efficiency.The distinction between efficacy and efficiency is not always carefully maintained in published sources, so it is not uncommon to see "efficiencies" expressed in lumens per watt, or "efficacies" expressed as a percentage.

  9. Grade (slope) - Wikipedia

    en.wikipedia.org/wiki/Grade_(slope)

    as a percentage, the formula for which is which is equivalent to the tangent of the angle of inclination times 100. In Europe and the U.S. percentage "grade" is the most commonly used figure for describing slopes.