5,567 research outputs found

    Analysis of clamped skewed plates subjected to lateral uniform loading.

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    Linear and nonlinear analyses of skewed plates.

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    Near-inertial wave scattering by random flows

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    The impact of a turbulent flow on wind-driven oceanic near-inertial waves is examined using a linearised shallow-water model of the mixed layer. Modelling the flow as a homogeneous and stationary random process with spatial scales comparable to the wavelengths, we derive a transport (or kinetic) equation governing wave-energy transfers in both physical and spectral spaces. This equation describes the scattering of the waves by the flow which results in a redistribution of energy between waves with the same frequency (or, equivalently, with the same wavenumber) and, for isotropic flows, in the isotropisation of the wave field. The time scales for the scattering and isotropisation are obtained explicitly and found to be of the order of tens of days for typical oceanic parameters. The predictions inferred from the transport equation are confirmed by a series of numerical simulations. Two situations in which near-inertial waves are strongly influenced by flow scattering are investigated through dedicated nonlinear shallow-water simulations. In the first, a wavepacket propagating equatorwards as a result from the β\beta-effect is shown to be slowed down and dispersed both zonally and meridionally by scattering. In the second, waves generated by moving cyclones are shown to be strongly disturbed by scattering, leading again to an increased dispersion.Comment: Accepted for publication in Phys. Rev. Fluid

    Effective Assessment of Power Standing Device to Adults with Permanent Lower Limb Paralysis

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    Introduction: Standing routine is a known beneficial daily activity for both healthy and disabled persons, especially those with permanent lower limb paralysis. However, the prescription of standing device for adults with permanent paralysis was inadequate and non-standard in existing local practice because of lack of good design and evidence based funding support. Objective: In view of the availability of new advances in power standing device, we aim to perform an effective health technology assessment (HTA) from professional and users perspectives to develop the decision pathway in prescription for long term home use. Methodology: A functional test and social cost analysis was performed on one high cost new standing mobile devices in recent market. A practical workshop and surveys were performed to collect feedback from 24 healthcare professionals and 8 expert users on a spectrum of new standing mobile device. Results: From the survey results, there was consensus among all participants that ‘Standing’ as daily routine at home is essential and beneficial. 62.5% of healthcare professionals would provide training to users and their cares to facilitate users to perform standing at home. Eight factors were identified from factor analysis in affecting the choice of standing devices for home use by healthcare professionals and users. Users scored high (mean=9.25/10) in “compliance with the new power standing mobile device”. The cost analysis showed considerable savings in social costs in using even the high-cost power standing mobile device. Discussion: The group welcomed power standing device with or without mobile function to support their standing activity at home. A possible clinical decision for prescribing different standing devices with identified factors was summarized. Conclusion: More recent researches have reported the negative health issues associated with prolonged sitting. With more innovative product designs, the power standing devices with or without mobile function is a new concept welcomed by both healthcare professionals and users in promotion of their health, preventing complications as well as independent living in home environment. A larger scale of HTA with structured cost-effectiveness analysis is essential to inform the healthcare resources planners

    The Effect of Sodium on the Catalytic Activity of ZnO-Al2O3/ZSM-5 and SnO-Al2O3/ZSM-5 for the Transesterification of Vegetable Oil with Methanol

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    In order to elucidate the effect of sodium on the activity of ZSM-5 supported metal oxides catalysts (ZnO-Al2O3/ZSM-5 and SnO-Al2O3/ZSM-5) for the transesterification of soybean oil with methanol, ZSM-5 supported metal oxides were prepared with and without sodium hydroxide by impregnation. The metal compositions of the ZSM-5 supported metal oxide catalysts and the metal concentrations dissolved from the catalysts to the methylester phase were measured by SEM-EDS and inductive coupled plasma spectroscopy, respectively. The catalytic activity of ZnO-Al2O3/ZSM-5 and SnO-Al2O3/ZSM-5 containing sodium did not originate from surface metal oxides sites, but from surface sodium sites or dissolved sodium leached from the catalyst surface
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