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A shear mode magnetorheological (MR) elastomer damper is designed and manufactured, in which the MR elastomer is made by mixing RTV silicone, carbonyl iron particles and silicone oil, and solidifying under magnetic field. A flexible cantilever rotor system with single disk is constructed, and the controllability, effectiveness and stability of vibration control for the imbalance response of the rotor system using the MR damper are experimentally studied. From the test, it is found that as the strength of applied magnetic field increases, the damping and stiffness of the damper are increased; the critical speeds of the rotor system supported on the MR damper is increased distinctly, and the vibration at two critical speeds are restrained; the on-off control method may be used to control the rotor vibration while passing through the two critical speeds. The study shows that the shear mode MR elastomer damper is suitable for active vibration control of flexible rotor.

An omnidirectional antenna is presented. It is composed of dipole array. This antenna operates at 2.4 GHz for WLAN. As the radiation element, the dipole has a minimized height for reducing the size of antenna. Its size is 27mm high and 75mm length. Four dipoles that encircle a metal cylinder at the radial direction form an omnidirectional element. Along the axial direction there are three omnidirectional elements with the distance of 101mm. The gain of this antenna is 7.1 dBi at 2.4 GHz and the gain variation in azimuth plane less than 0.5dB.