  By adopting a citation-based recursive ranking method for patents the
evolution of new fields of technology can be traced. Specifically, it is
demonstrated that the laser / inkjet printer technology emerged from the
recombination of two existing technologies: sequential printing and static
image production. The dynamics of the citations coming from the different
"precursor" classes illuminates the mechanism of the emergence of new fields
and give the possibility to make predictions about future technological
development. For the patent network the optimal value of the PageRank damping
factor is close to 0.5; the application of d=0.85 leads to unacceptable ranking
results.
