  In this paper, we prove necessary and sufficient conditions for a
sense-preserving harmonic function to be absolutely convex in the open unit
disk. We also estimate the coefficient bound and obtain growth, covering and
area theorems for absolutely convex harmonic mappings. A natural generalization
of the classical Bernardi type operator for harmonic functions is considered
and its connection between certain classes of uniformly starlike harmonic
functions and uniformly convex harmonic functions is also investigated. At the
end, as applications, we present a number of results connected with
hypergeometric and polylogarithm functions.
