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  2. Stellar structure - Wikipedia

    en.wikipedia.org/wiki/Stellar_structure

    In massive stars (greater than about 1.5 M ☉), the core temperature is above about 1.8×10 7 K, so hydrogen-to-helium fusion occurs primarily via the CNO cycle. In the CNO cycle, the energy generation rate scales as the temperature to the 15th power, whereas the rate scales as the temperature to the 4th power in the proton-proton chains. [ 2 ]

  3. Structure - Wikipedia

    en.wikipedia.org/wiki/Structure

    A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. [1] Material structures include man-made objects such as buildings and machines and natural objects such as biological organisms , minerals and chemicals .

  4. Wikipedia - Wikipedia

    en.wikipedia.org/wiki/Wikipedia

    The English Wikipedia, with over 7 million articles, remains the largest of the editions, which together comprise more than 64 million articles and attract more than 1.5 billion unique device visits and 13 million edits per month (about 5 edits per second on average) as of April 2024.

  5. Mathematical structure - Wikipedia

    en.wikipedia.org/wiki/Mathematical_structure

    [1] Map between two sets with the same type of structure, which preserve this structure [ morphism : structure in the domain is mapped properly to the (same type) structure in the codomain ] is of special interest in many fields of mathematics.

  6. Fine-structure constant - Wikipedia

    en.wikipedia.org/wiki/Fine-structure_constant

    This has a relative standard uncertainty of 1.6 × 1010. [ 1 ] This value for α gives µ 0 = 4 π × 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 .

  7. Wendelstein 7-X - Wikipedia

    en.wikipedia.org/wiki/Wendelstein_7-X

    Operational phase 1 continued (OP1.2) in 2017 [34] to test the (uncooled) divertor. [35] [24] [36] Wendelstein 7-X during OP1.2b. In June 2018 a record ion temperature of about 40 million degrees, a density of 0.8 × 10 20 particles/m 3, and a confinement time of 0.2 second yielded a record fusion product of 6 × 10 26 degree-seconds per cubic ...

  8. Phases of ice - Wikipedia

    en.wikipedia.org/wiki/Phases_of_ice

    At near-IR wavelengths, the characteristics of the 1.65, 3.1, and 4.53 μm water absorption lines are dependent on the ice temperature and crystal order. [160] The peak strength of the 1.65 μm band as well as the structure of the 3.1 μm band are particularly useful in identifying the crystallinity of water ice. [161] [162]

  9. Thermophotovoltaic energy conversion - Wikipedia

    en.wikipedia.org/wiki/Thermophotovoltaic_energy...

    Based on this temperature, energy production is maximized when the bandgap is about 1.4 eV, in the near infrared. This just happens to be very close to the bandgap in doped silicon, at 1.1 eV, which makes solar PV inexpensive to produce. [3] This means that all of the energy in the infrared and lower, about half of AM1.5, goes to waste.