Outside the umbral cone is that of the penumbra, within which the sun is partially hidden by the moon.
"Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 10" by Various
The sense-cells are innervated, as before, from the sub-umbral nerve-ring.
"Encyclopaedia Britannica, 11th Edition, Volume 14, Slice 2" by Various
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The chromospheric energy losses in umbral regions are 3-5 times lower than in quiet Sun, but the energy supplied by the waves seems to be similar.
Magneto-acoustic wave energy from numerical simulations of an observed sunspot umbra
Roman, The Umbral Calculus, Academic Press, New York, 1984.
Stochastic Service Systems, Random Interval Graphs and Search Algorithms
There is a well-developed branch of mathematics called Umbral Calculus [29, 30], which consider the case when k ∈ N.
Mellin Transforms of the Generalized Fractional Integrals and Derivatives
In this paper, we investigate some interesting properties arising from umbral calculus.
Umbral calculus associated with Bernoulli polynomials
The umbral calculus is the study of umbral algebra and modern classical umbral calculus can be described as a systematic study of the class of Sheffer sequences (see ).
Umbral calculus associated with Bernoulli polynomials
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