▎ 摘　　要

We investigate the transport properties of Dirac fermions through velocity-modulation structures, with the Fermi velocity inside the barriers larger than the one outside. It is shown that the transmission exhibits pseudo-periodicity with the incident angle below the critical transmission angle, but attenuates exponentially in the opposite situation. It is found that in the transmission, (1) the pseudo-periodicity turns to periodicity with suitable modulation; (2) line-type peaks appear in the exponential attenuation region for multiple velocity barriers; (3) peak splitting occurs with the number of the velocity barriers increasing. Some sharp oscillations with the falling-edge slopes close to infinity exist in the conductance profile. These novel transport properties suggest significant potential applications in graphene-based devices.