  The tuning process of a large apparatus of many components could be
represented and quantified by constructing parameter-tuning networks. The
experimental tuning of the ion source of the neutral beam injector of HT-7
Tokamak is presented as an example. Stretched-exponential cumulative degree
distributions are found in the parameter-tuning networks. An active walk model
with eight walkers is constructed. Each active walker is a particle moving with
friction in an energy landscape; the landscape is modified by the collective
action of all the walkers. Numerical simulations show that the parameter-tuning
networks generated by the model also give stretched exponential functions, in
good agreement with experiments. Our methods provide a new way and a new
insight to understand the action of humans in the parameter-tuning of
experimental processes, is helpful for experimental research and other
optimization problems.
