The subject of this book is multidisciplinary. Activation functions are of interest for fundamental as well as applied research. We give the readers both directions. From the fundamental science point of view activation functions are of special interest in abstract research in approximation theory, functional analysis and probability theory. From the applied mathematics and modeling point of view activation functions find their place in areas of natural and social sciences, physics, nucleation theory, neural networks and engineering, etc. This book is for undergraduate students enrolling master or PhD programs in applied mathematics and mathematical modeling. A basic knowledge of mathematical analysis, linear algebra and calculus is needed for easier reading. Readers with computational programming skills may find new ideas for writing their personal programs to make graphics of various activation functions.

Prof. Nikolay Kyurkchiev, Prof. Anton Iliev and Prof. Svetoslav Markov are from University of Plovdiv Paisii Hilendarski, FMI and from Bulgarian Academy of Sciences, IMI, respectively. Up to now, they have more than 500 papers in the field of Numerical Analysis, Approximation Theory, Mathematical Modeling and Distributed Applications.