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The California Job Case was a compartmentalized box for printing in the 19th century, sizes corresponding to the commonality of letters. The frequency of letters in text has been studied for use in cryptanalysis, and frequency analysis in particular, dating back to the Arab mathematician al-Kindi (c. AD 801–873 ), who formally developed the method (the ciphers breakable by this technique go ...
The set of rational numbers is not complete. For example, the sequence (1; 1.4; 1.41; 1.414; 1.4142; 1.41421; ...), where each term adds a digit of the decimal expansion of the positive square root of 2, is Cauchy but it does not converge to a rational number (in the real numbers, in contrast, it converges to the positive square root of 2).
The base "Roman fraction" is S, indicating 1 ⁄ 2. The use of S (as in VIIS to indicate 7 1 ⁄ 2) is attested in some ancient inscriptions [45] and also in the now rare apothecaries' system (usually in the form SS): [44] but while Roman numerals for whole numbers are essentially decimal, S does not correspond to 5 ⁄ 10, as one might expect ...
μ is the dynamic viscosity of the fluid (Pa·s = N·s/m 2 = kg/(m·s)); Q is the volumetric flow rate, used here to measure flow instead of mean velocity according to Q = π / 4 D c 2 <v> (m 3 /s). Note that this laminar form of Darcy–Weisbach is equivalent to the Hagen–Poiseuille equation, which is analytically derived from the ...
The current annual GMST is about 15 °C (59 °F), [6] though monthly temperatures can vary almost 2 °C (4 °F) above or below this figure. [7] The global average and combined land and ocean surface temperature show a warming of 1.09 °C (range: 0.95 to 1.20 °C) from 1850–1900 to 2011–2020, based on multiple independently produced datasets.
From 2011 to 2021, renewable energy grew from 20% to 28% of global electricity supply. Power from the sun and wind accounted for most of this increase, growing from a combined 2% to 10%. Use of fossil energy shrank from 68% to 62%. [7] In 2022, renewables accounted for 30% of global electricity generation and are projected to reach over 42% by ...