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Fig. 1. A sample graph of |
Approximations
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| {\rm Ei}(x) = \gamma + \ln |x| + \sum_{k=1}^\infty \frac{x^k}{k\cdot k!} |
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| {\rm Ei}(x) = e^x \, \left[ \frac{1}{x} + \sum_{k=2}^\infty \frac{(k-1)!}{x^k} \right] |
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| {\rm Ei}(-x) \sim \gamma + \ln x |
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| {\rm Ei}(x) \sim \gamma + \ln x |
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Application
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The real-value positive function of two real-value positive arguments (time and radial coordinate ):
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and is widely used in radial heat-mass transfer simulations.
References
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https://www.wolframalpha.com/input/?i=Ei(x)
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