Finite element analysis on deflection control of plates with piezoelectric actuators

A finite element model for the deflection control of plates with piezoelectric actuators is presented. This model contains an actuator element, an adhesive interface element and an eight-node isoparametric plate element. The actuator element developed here is based on first-order shear deformation theory. An analytical solution is also derived in comparison with results using the finite element model. The analyses articulate separate response of the plate; actuators and the adhesive give the flexible meshing advantage of solving the- smart structure problem with any type of boundary conditions and geometry configuration.     

Digital audio watermarking using minimum-amplitude scaling on optimized DWT low-frequency coefficients

This work presents an audio watermarking scheme using minimum-amplitude scaling on the optimized lowest-frequency coefficients in the wavelet domain. Signal-to-noise ratio (SNR), bit-error-rate (BER) and Perceptual Evaluation of Audio Quality (PEAQ) are commonly utilized performance indexes in measuring the fidelity, robustness and quality of watermarking algorithms. However, there is a tradeoff relationship between audio quality and robustness. To overcome the drawback, this paper aims in proposing an optimization-based scaling scheme using optimal modification of low-frequency amplitude in the wavelet domain. A function connecting the multi-coefficients, composed of arbitrary scaling on the lowest DWT coefficients, and the group SNR of these coefficient is derived. Karush-Kuhn-Tucker (KKT) theorem and minimum length play two essential roles to obtain the optimal modification of low-frequency amplitude with optimal scaling factors. Furthermore, the almost invariant feature of these optimized scaling factors hold demonstrates resistance to amplitude modification manipulation. To practically evaluate the watermarked audio quality, an objective measurement using the PEAQ is also performed as well. Experimental results confirm that the embedded audio in the proposed method has high SNR, low BER, and good PEAQ, indicating strong robustness against various attacks, such as re-sampling, amplitude modification, and mp3 compression.

     

Adaptive audio watermarking via the optimization point of view on the wavelet-based entropy

This study aims to present an adaptive audio watermarking method using ideas of wavelet-based entropy (WBE). The method converts low-frequency coefficients of discrete wavelet transform (DWT) into the WBE domain, followed by the calculations of mean values of each audio as well as derivation of some essential properties of WBE. A characteristic curve relating the WBE and DWT coefficients is also presented. The foundation of the embedding process lies on the approximately invariant property demonstrated from the mean of each audio and the characteristic curve. Besides, the quality of the watermarked audio is optimized. In the detecting process, the watermark can be extracted using only values of the WBE. Finally, the performance of the proposed watermarking method is analyzed in terms of signal to noise ratio, mean opinion score and robustness. Experimental results confirm that the embedded data are robust to resist the common attacks like re-sampling, MP3 compression, low-pass filtering, and amplitude scaling.