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Featured Application: An active control approach to mitigate low-frequency noise propagating through an open top-hung window, while allowing natural ventilation. The push for greater urban sustainability has increased the urgency of the search for noise mitigation solutions that allow for natural ventilation into buildings. Although a viable active noise control (ANC) solution with up to 10 dB of global attenuation between 100 Hz and 1000 Hz was previously developed for an open window, it had limited low-frequency performance below 300 Hz, owing to the small loudspeakers used. To improve the low-frequency attenuation, four passive radiator-based speakers were affixed around the opening of a top-hung ventilation window. The active control performance between 100 Hz and 700 Hz on a single top-hung window in a full-sized mock-up apartment room was examined. Active attenuation came close to the performance of the passive insulation provided by fully closing the window for expressway traffic and motorbike passing noise types. For a jet aircraft flyby, the performance of active attenuation with the window fully opened was similar to that of passive insulation with fully closed windows. In the case of low-frequency compressor noise, active attenuation's performance was significantly better than the passive insulation. Overall, between 8 dB and 12 dB of active attenuation was achieved directly in front of the window opening, and up to 10.5 dB of attenuation was achieved across the entire room. [ABSTRACT FROM AUTHOR]

The gradual adaptation and possibility of divergence hinder the active noise control system from being applied to a wider range of applications. Selective active noise control has been proposed to rapidly reduce noise by selecting a pre-trained control filter for different primary noise detected without an error microphone. For stationary noise, considerable noise reduction performance with a short selection period is obtained. For non-stationary noise, more restrictive requirements are imposed on instant convergence, as it leads to faster tracking and better noise reduction performance. To speed up a selective filtered active noise control system, empirical wavelet transform is introduced here to accurately and instantaneously extract the frequency information of primary noise. The boundary of the first intrinsic mode function of random noises is extracted as the instant signal feature. Primary noise is attenuated immediately by picking the optimal pre-trained control filter labeled by the nearest boundary. The storage requirement for a pre-trained control filter library is reduced. Instant control is obtained, and the instability caused by output saturation is overcome. With more concentrated energy distribution, better noise reduction performance is achieved by the proposed algorithm compared to conventional and selective active noise control algorithms. Simulation results validate these advantages of the proposed algorithm. [ABSTRACT FROM AUTHOR]

The leaky filtered-input least mean square (LFxLMS) algorithm is widely used in active noise control applications to minimize the degradation of attenuation performance due to output saturation distortion. However, the leak factor, which is critical in determining the steady-state error and robustness of the algorithm, is usually selected through trial and error. This letter proposes a leak factor selection approach, which ensures the LFxLMS algorithm converges to its optimal solution under the average-output-power constraint and can be readily derived in practice. Both broadband and narrowband cases are considered in the derivation without the independence assumption, and the simulations are conducted based on real primary and secondary paths to verify its effectiveness. [ABSTRACT FROM AUTHOR]

Looks at the discovery of high-T superconducters which experiments has revealed that phase diagrams of La...-...Sr...CuO... and YBa...Cu...O...+... resemble each other. Indepth look at the experiment; Details on the results and discussion.

The electron structure of the typical calcium phosphate ceramic, hydroxyapatite (OHAP), is investigated by the use of the tight-binding recursion method. The local density of states, partial density of states, structural energy and charge transfer are calculated, as well as the interatomic energy between atoms and bond order integral. Some physical and chemical properties of OHAP are discussed. The calculated results show that both the OH group and the PO4 group can be regarded as individual structure units in OHAP owing to strong interaction between atoms. Meanwhile, the atomic structure of a grain boundary is determined on the basis of the near-coincidence site lattice model with consideration of the bond length in the crystal and the lattice distortion. The electron structure and energy of a Sigma = 7 grain boundary are calculated. The results show that a grain boundary with a slight lattice misfit has a lower energy. [ABSTRACT FROM AUTHOR]

Transmission electron micrographs of a multilayer film consisting of 360 alternating layers of plasma deposited hydrogenated amorphous silicon and silicon nitride show that each 28-Å-thick layer is remarkably flat and uniform. Within the first 1000 Å near the glass substrate the regular growth of the layers is disturbed by instabilities which resemble dislocations in the layering. Electron microscopy of compositional layering may prove to be an important tool for studying the growth mechanism during plasma deposition. [ABSTRACT FROM AUTHOR]

Analyzes the structure of polyhydro particles using HRTEM and the energy spectrum method. Preparation of nanocrystalline transition; Storage of hydrogen in nano transition metal particles; Ability of this stored hydrogen; Details on the structure of the shell and the core of hydrogen storage particles.

Most of the non-acoustic methods for towed array shape estimation are based on the incorrect original Paidoussis equation. A comparison between solution to the original and revised Paidoussis equation is made to prove the significance of utilising the latter. In addition, considering relative characteristics of the revised Paidoussis equation and the critical point which exists on the cylinder, the minimum length of damping section added at the end of the cylinder is derived. [ABSTRACT FROM AUTHOR]

Abstract: Gold nanoparticles supported on carbon nanotubes (CNTs) were obtained by using electroless plating technique. High-resolution transmission electron microscopy evidenced the high-density and homogeneous dispersion of spherical gold nanoparticles on the outer surfaces of the carbon nanotubes, with a sharp particle size distribution centered at around 3–4 nm of diameter. The resultant hybrid nanostructures have potential application for being used as novel gold nanocatalysts. [Copyright &y& Elsevier]