Table 2 Standard deviation characteristics of trigonometric functions.

From: Deep multiscale feature fusion network with dual attention for rolling bearing remaining useful life prediction

Features

Calculation formulas

Standard deviation of the tangent

\(X_{a\tanh } = \sigma \left( {In\left[ {x_{i} + \sqrt {x_{i}^{2} + 1} } \right]} \right)\)

Inverse hyperbolic sine standard deviation

\(X_{a\sinh } = \sigma \left( {\frac{1}{2}In\left( {\frac{{1 + x_{i} }}{{1 - x_{i} }}} \right)} \right)\)

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