Head-related transfer functions (HRTFs) play an important role in spatial sound localization. The boundary element method (BEM) can be applied to calculate HRTFs from non-contact visual scans. Because of high computational complexity, HRTF simulations with BEM for the whole head and pinnae have only been performed for frequencies below 10 kHz. In this study, the fast multipole method (FMM) is coupled with BEM to simulate HRTFs for a wide frequency range. The basic approach of the FMM and its implementation are described. A mesh with over 70 000 elements was used to calculate HRTFs for one subject. With this mesh, the method allowed to calculate HRTFs for frequencies up to 35 kHz. Comparison to acoustically-measured HRTFs has been performed for frequencies up to 16 kHz, showing a good congruence below 7 kHz. Simulations with an additional shoulder mesh improved the congruence in the vertical direction. Reduction in the mesh size by 5% resulted in a substantially-worse representation of spectral cues. The effects of temperature and mesh perturbation were negligible. The FMM appears to be a promising approach for HRTF simulations. Further limitations and potential advantages of the FMM-coupled BEM are discussed.

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Bacteria induced infection remains a serious medical hazard to humans. Antibacterial polymeric materials, which can kill or inhibit bacteria by disrupting cell membranes, inhibiting certain enzymes, or interfering with the transcription or synthesis of DNA or RNA, have been applied to reduce or inhibit microbial drug resistance. Herein, amino acid-based ionic liquids (ILs) and poly­(ionic liquid) (PIL) membranes were synthesized and used as antibacterial materials to treat skin wounds infected by methicillin-resistant Staphylococcus aureus (MRSA). The effects of chirality (D- or L-enantiomers) and chemical bonding (ionic or covalent) of the amino acid groups attached to the IL (or PIL) on antibacterial properties were investigated. Both the ILs and PIL membranes containing D-enantiomeric amino acid groups exhibited higher antibacterial activities compared with those containing L-enantiomeric amino acids. In addition, the ionically-bonded PIL membranes showed higher antibacterial activities than the corresponding covalently-bonded polymeric membranes. These results indicate that both the chirality and chemical bonding type of amino acid groups affect the antimicrobial activity of the PIL membranes. Additionally, the amino acid-based PIL membranes accelerated the wound-healing process, alleviated local tissue inflammation, and reduced the influence of bacteria on vital organs (liver and spleen) in MRSA-infected mouse models, demonstrating the potential applications for antimicrobial wound dressing.

An efficient dynamic modelling approach was presented for planar parallel manipulator with flexible links. To increase the accuracy of the model, an improved curvature-based finite element method (ICFE) was developed for discretisation of the flexible links. Then, a novel approach for analysis of the coupling between rigid-body motion and flexible-body motion was proposed, and compared to the regular geometrical method, the proposed method was accurate and easy to implement. With the aforementioned proposed methods, the Kane equation was integrated to formulate the dynamic model of a 3RRR planar parallel manipulator. Finally, comparison studies were performed to validate the proposed ICFE and the integrated dynamic modelling method. Compared to the regular curvature-based finite element method (CFE), the ICFE exhibits improved accuracy with equivalent degrees of freedom. Additionally, the proposed integrated dynamic model shows a good agreement with the Abaqus model. Therefore, it was concluded that the proposed dynamic modelling method herein was efficient and accurate for parallel manipulators with flexible links, demonstrating reasonable potentials for model based control.