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The transverse vibration energy of a plate with a wedge-shaped profile can be trapped by acoustic black hole effect to its edge portion, in case the wedge thickness is diminished according to the power-law h(x) = εxm with m ≥ 2.0. The acoustic black hole effect exhibits potential ability for passive vibration control and energy harvesting. In this article, the transfer matrix method is adopted to establish and solve the dynamical model of acoustic black hole structure. Energy ratio is defined as a ratio of the energy trapped within the edge portion to that of the whole wedge, to illustrate the energy concentration effect. Analyses show that both the strain energy ratio and kinetic energy ratio of the acoustic black hole structure achieve the minimum when the wedge is in resonances, although these two kinds of energy come to peaks at this case. However, in the case of small length of the edge portion, the strain energy ratio reaches the highest peaks at the second and higher resonances, rather than at the first one. Generally, the best effect of energy concentration occurs when m ranges from 2.5 to 3.0. Reducing the truncation thickness and increasing the maximum height can improve the energy trapping.

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The diffusivity in the Ni-Al system with and without an alternating magnetic field (AMF) was investigated by the diffusion couple technique. It was found that the diffusion coefficient was increased with increasing AMF intensity. The enhanced diffusivity in the AMF can be ascribed to the increase in the dislocation density in the diffusion couples, which was demonstrated by the broadening of X-ray diffraction peaks. The higher dislocation density was induced by the magnetoplastic effect (MPE). The theoretical calculation based on the MPE is in agreement with the experimental values.

The demands of instant video communication have recently increased as a means to improve user experience. Meanwhile, the cache mechanism has become an effective technology used in video transmission so that delay jitter could be reduced to a insignificant value. We propose a novel video service quality assurance scheme in multirelay networks (MRNs) with cache. Both wireless channel state information on the transmitting side and optimal receiver schemes on the receiving side are considered in the proposed scheme. We derive closed form expressions of video streaming for cache-based MRN and investigate the impact of cache length when it is changed. Then, we proved that the optimal solution is difficult to acquire, and the suboptimal solution could be achieved by decomposing the original optimization problem into several simpler subproblems, which include graph and convex optimization. Specifically, we obtain a limit for the cache queuing model in MRNs. Detailed algorithms with corresponding theoretical reasoning are provided as well. Simulations demonstrate the effectiveness of our proposed scheme by comparing with some other existed high-video-quality transmission schemes. The analysis also shows that our scheme outperforms others in jitter reducing.