The two plasma sources using a concentrically three-segmented plasma (ion) emitter are developed, with which the parallel and perpendicular flow shears can be controlled, respectively. In the case of parallel flow-shear experiments, the drift-like, ion-acoustic-like, Kelvin-Helmholtz, and their coupled instabilities are found to be excited by the parallel flow shear. In the case of perpendicular flow-shear experiments, on the other hand, the drift-like instability which exists in the edge (density-gradient) region is suppressed by the perpendicular flow shear in the central region. These results show the importance of combined effects of radial density gradient and parallel/perpendicular flow shears on the low-frequency instabilities in magnetized plasmas.