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In a third layer, the logarithms of rational numbers r = a / b are computed with ln(r) = ln(a) − ln(b), and logarithms of roots via ln n √ c = 1 / n ln(c).. The logarithm of 2 is useful in the sense that the powers of 2 are rather densely distributed; finding powers 2 i close to powers b j of other numbers b is comparatively easy, and series representations of ln(b) are ...
The first nanotube ropes (20 mm long) whose tensile strength was published (in 2000) had a strength of 3.6 GPa, still well below their theoretical limit. [41] The density is different depending on the manufacturing method, and the lowest value is 0.037 or 0.55 (solid). [37]
where f t,d is the raw count of a term in a document, i.e., the number of times that term t occurs in document d. Note the denominator is simply the total number of terms in document d (counting each occurrence of the same term separately). There are various other ways to define term frequency: [5]: 128 the raw count itself: tf(t,d) = f t,d
Abundance (atom fraction) of the chemical elements in Earth's upper continental crust as a function of atomic number; [5] siderophiles shown in yellow Graphs of abundance against atomic number can reveal patterns relating abundance to stellar nucleosynthesis and geochemistry.
NASA's Wilkinson Microwave Anisotropy Probe (WMAP) project's nine-year data release in 2012 estimated the age of the universe to be (13.772 ± 0.059) × 10 9 years (13.772 billion years, with an uncertainty of plus or minus 59 million years).
6.37 ⋅ 10 7 at 273.15 K; 5.71 ⋅ 10 7 at 300K; 4.15 ⋅ 10 7 at 400K. [41] International Annealed Copper Standard (IACS) pure =1.7×10 −8 Ω•m =58.82×10 6 Ω −1 •m −1. For main article, see: Copper in heat exchangers. The TPRC recommended values are for well annealed 99.999% pure copper with residual electrical resistivity of ρ 0 ...
In fact, under clear skies a solar panel placed horizontally at the north or south pole at midsummer receives more sunlight over 24 hours (cosine of angle of incidence equal to sin(23.5°) or about 0.40) than a horizontal panel at the equator at the equinox (average cosine equal to 1/ π or about 0.32).
While in 1977 prices for crystalline silicon cells were about $77 per watt, average spot prices in August 2018 were as low as $0.13 per watt or nearly 600 times less than forty years ago. Prices for thin-film solar cells and for c-Si solar panels were around $.60 per watt. [ 43 ]