Active control of sound radiation from piezoelectric laminated cylindrical shells is theoretically investigated in the wavenumber domain. The governing equations of the smart cylindrical shells are derived by using first-order shear deformation theory. The smart layer is divided into lots of actuator patches, each of which is coated with two very thin electrodes at its inner and outer surfaces. Proportional derivative negative feedback control is applied to the actuator patches and the stiffness of the controlled layer is derived in the wavenumber domain. The equivalent driving forces and moments generated by the piezoelectric layer can produce distinct sound radiation. Large actuator patches cause strong wavenumber conversion and fluctuation of the far-field sound pressure, and do not make any contribution to sound reduction. Nevertheless, suitable small actuator patches induce weak wavenumber conversion and play an important role in the suppression of vibration and acoustic power. The derivative gain of the active control can effectively suppress sound radiation from smart cylindrical shells. The effects of small proportional gain on the sound field can be neglected, but large proportional gain has a great impact on the acoustic radiation of cylindrical shells. The influence of different piezoelectric materials on the acoustic power is described in the numerical results.
Sensitive and accurate detection of tumor markers is significant for early diagnosis and cancer treatment, but it remains challenging. A promising solution is to integrate different detection strategies into the same sensing platform. Herein, a BiOBr 0.8 I 0.2 /CoS x nanocomposite with high photoelectrochemical (PEC) and electrochemical (EC) activity is prepared by a hydrothermal method and afterward in situ visible light irradiation. The light irradiation makes BiOBr 0.8 I 0.2 /CoS turn into BiOBr 0.8 I 0.2 /CoS x (x = 1−2), and the photocurrent thus increases by 5 times. Compared with the BiOBr 0.8 I 0.2 , the photocurrent of the composite increased by 74 times due to the formation of a heterojunction and the enhanced sensitization of CoS x . Furthermore, the nanocomposite can exhibit a high cathodic signal. Therefore, it is used to construct a PEC and EC dual-mode sensing platform for the detection of human epidermal growth factor receptor-2 (HER2), by combining with the aptamer of HER2. Due to the steric hindrance of HER2, the PEC and EC signals change with HER2 concentration. Under the optimized conditions, the sensing platform shows quite low detection limits (0.31 and 1.06 pg/mL) and large linear ranges (0.001−10 and 0.005−15 ng/mL, for PEC and EC mode, respectively). It also demonstrates high selectivity, excellent stability, and good applicability. The sensing platform can also be applied to detect other markers by replacing the recognition element.
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