Cavitation has been widely used in wastewater degradation, material synthesis and biomedical field under dual-frequency acoustic excitation. The applications of cavitation are closely related to the power (i.e. the rate of internal energy accumulation) during bubble collapse. The Keller–Miksis equation considering liquid viscosity, surface tension and liquid compressibility is used to describe the radial motion of the bubble. The model is built in predicting the power during bubble collapse under dual-frequency acoustic excitation. The influences of parameters (i.e. phase difference, frequency difference, and amplitude ratio) on the power are investigated numerically. With the increase of phase difference, the power can be fluctuated in a wide range at all conditions. Three typical characteristics of the power appear under the effects of frequency difference and amplitude ratio. With the increase of amplitude ratio, if the frequency difference is small, the power has two maximum values; and if the frequency difference is medium, there is a maximum value. Otherwise, the power monotonously decreases. The results can provide theoretical references for the selections of experimental parameters of sonoluminescence and sonochemistry in the dual-frequency acoustic field.

This paper presents a printed dual band monopole antenna working below 250 MHz using meander line and an added stub. Meander line approach is used to reduce the size of the low frequency monopole. The proposed antenna is fed by microstrip line and printed on FR-4 substrate with an overall size of 290 x 83 mm2. The added stub tuned dual band operation at 114 MHz and 221 MHz with measured reflection coefficient of -19 dB at both bands. The antenna has omni-directional characteristics with efficiency greater than 90% and gain of 1.87, 1.7 dBi at both bands respectively. The antenna design is optimized through a detailed parametric study. This study includes varying stub, Meander, feed and ground dimensions. The antenna has been fabricated and measured where dual band operation in the MHz range is verified.