In this letter, a class of honeycomb acoustic metamaterial possessing lightweight and yet sound-proof properties is designed, theoretically proven, and then experimentally verified. It is here reported that the proposed metamaterial having a remarkably small mass per unit area at 1.3 kg/m2 can achieve low frequency (<500 Hz) sound transmission loss (STL) consistently greater than 45 dB. Furthermore, the sandwich panel which incorporates the honeycomb metamaterial as the core material yields a STL that is consistently greater than 50 dB at low frequencies. The proposed metamaterial is promising for constructing structures that are simultaneously strong, lightweight, and sound-proof.

Ammonia-oxidizing archaea (AOA) and bacteria (AOB) communities within the surface sediments of Lake Taihu, a large eutrophic freshwater lake in China, were investigated using molecular approaches targeting the ammonia monooxygenase subunit A (amoA) gene. Large intra-lake variability in the composition and the relative abundance of both groups of ammonia-oxidizing prokaryotes was observed. Archaeal amoA far outnumbered bacterial amoA at most sites except those located in the Eastern Taihu Bay. This bay, which is used for intensive pen aquaculture, harboured the most unique AOA communities but was dominated by AOB in terms of relative abundance. Accumulation of organic substances rather than presence of submersed macrophytes significantly influenced the relative abundance of AOA. In contrast, shifts in the abundance of AOB were not found to be significantly related to the investigated environmental parameters. Phylogenetic analysis showed that all archaeal amoA sequences fell within either the Crenarchaeotal Group (CG) I.1b or the CG I.1a subgroup, and all AOB clustered exclusively with the genus Nitrosomonas. These findings represent the first detailed survey of AOA in eutrophic freshwater lake sediments by demonstrating that AOA dominate the ammonia-oxidizing communities, and are negatively correlated with the accumulation of organic substances.

Bonding a two-dimensional planar array of small lead discs on an aluminum plate with silicone rubber is shown numerically to focus low-frequency flexural guided waves. The "effective mass density profile" of this type of elastic metamaterials (EMMs), perpendicular to wave propagation direction, is carefully tailored and designed, which allows rays of flexural A 0 mode Lamb waves to bend in succession and then focus through a 7 Â 9 planar array. Numerical simulations show that Lamb waves can be focused beyond EMMs region with amplified displacement and yet largely retained narrow banded waveform, which may have potential application in structural health monitoring. V C 2013 AIP Publishing LLC. [http://dx.

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A direct curvature sensing measurement based on the flexoelectricity of Ba 0.64 Sr 0.36 TiO 3 (BST) material through electromechanical coupling is proposed and developed in this paper. The curvature sensing was demonstrated in four point bending tests of a beam with bonded BST curvature sensors under different applied loads with low time-harmonic frequencies from 0.5 to 3 Hz. A shear lag concept which describes the efficiency of the loading transfer from the epoxy bonding layer was taken into account in extracting the actual curvature from the sensor measurement. A finite element analysis has been performed to estimate the curvature transfer efficiency and the bonding layer thickness is found to be a critical parameter in determining the curvature transfer. Experimental results showed a good linearity of charge output dependence on curvature inputs in a limited frequency range and showed a curvature sensitivity of 30.78 pC m, in comparison with 32.48 pC m from theoretical predictions. Using the measured curvature, the bending stiffness of the beam was then obtained from the experimentally obtained moment-curvature curve. This work demonstrated that the flexoelectric BST sensor provides a direct curvature measurement instead of using a traditional strain gage sensor through interpolation, and thus offers an important avenue for on-line and in situ structural health monitoring.

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Magnetodielectric response in 0.36BiScO3-0.64PbTiO3/La0.7Sr0.3MnO3 thin films and the corresponding model modifications J. Appl. Phys. 110, 046103 (2011); 10.1063/1.3610421 Microstructural and optical properties of Ba 0.5 Sr 0.5 Ti O 3 thin film deposited by pulsed laser deposition for low loss waveguide applications

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