  We consider losses in monolayer graphene nanoresonator connected with Joule
dissipation (heating) caused by valley currents stipulated by synthetic
electric fields . These synthetic electric fields arise in graphene membrane
due to periodic in time gauge fields generated there by external periodic
electromotive force. This mechanism accounts for essential part (about 40
percents) of losses in graphene nanoresonator and is specific just for
graphene.
  The ways of the minimization of these Joule dissipation (increase of the
quality-factor of the electromechanical system) are discussed. It is explained
why one can increase quality-factor by correctly chosen combination of strains
(by strain engineering). Besides it is shown that quality-factor can be
increased by switching on a magnetic field perpendicular to graphene membrane.
