502 research outputs found

    Detecting Delamination via Nonlinear Wave Scattering in a Bonded Elastic Bar

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    In this paper we examine the effect of delamination on wave scattering, with the aim of creating a control measure for layered waveguides of various bonding types. Previous works have considered specific widths of solitary waves for the simulations, without analysing the effect of changing the soliton parameters. We consider two multi-layered structures: one containing delamination "sandwiched" by perfect bonding and one containing delamination but "sandwiched" by soft bonding. These structures are modelled by coupled Boussinesq-type equations. Matched asymptotic multiple-scale expansions lead to coupled Ostrovsky equations in soft bonded regions and Korteweg-De Vries equations in the perfectly bonded and delaminated region. We use the Inverse Scattering Transform to predict the behaviour in the delaminated regions. In both cases, numerical analysis shows that we can predict the delamination length by changes in the wave structure, and that these changes depend upon the Full Width at Half Magnitude (FWHM) of the incident soliton. In the case of perfect bonding, we derive a theoretical prediction for the change and confirm this numerically. For the soft bonding case, we numerically identify a similar relationship using the change in amplitude. Therefore we only need to compute one curve to determine the behaviour for any incident solitary wave, creating a framework for designing measurement campaigns for rigorously testing the integrity of layered structures.Comment: 12 pages, 7 figure

    Phosphatase activity and organic phosphorus turnover on a high Arctic glacier

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    Arctic glacier surfaces harbour abundant microbial communities consisting mainly of heterotrophic and photoautotrophic bacteria. The microbes must cope with low concentrations of nutrients and with the fact that both the dissolved and debris-bound nutrient pools are dominated by organic phases. Here we provide evidence that phosphorus (P) is deficient in the supraglacial environment on a Svalbard glacier, we quantify the enzymatic activity of phosphatases in the system and we estimate the contribution of the microbes to the cycling of the dominant organic P in the supraglacial environment. Incubation of cryoconite debris revealed significant phosphatase activity in the samples (19–67 nmol MUP g<sup>−1</sup> h<sup>−1</sup>). It was inhibited by inorganic P during incubations and had its optimum at around 30°C. The phosphatase activity measured at near-in situ temperature and substrate concentration suggests that the available dissolved organic P can be turned over by microbes within ~3–11 h on the glacier surface. By contrast, the amount of potentially bioavailable debris-bound organic P is sufficient for a whole ablation season. However, it is apparent that some of this potentially bioavailable debris-bound P is not accessible to the microbes

    A comparison of the Bravyi-Kitaev and Jordan-Wigner transformations for the quantum simulation of quantum chemistry

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    The ability to perform classically intractable electronic structure calculations is often cited as one of the principal applications of quantum computing. A great deal of theoretical algorithmic development has been performed in support of this goal. Most techniques require a scheme for mapping electronic states and operations to states of and operations upon qubits. The two most commonly used techniques for this are the Jordan-Wigner transformation and the Bravyi-Kitaev transformation. However, comparisons of these schemes have previously been limited to individual small molecules. In this paper we discuss resource implications for the use of the Bravyi-Kitaev mapping scheme, specifically with regard to the number of quantum gates required for simulation. We consider both small systems which may be simulatable on near-future quantum devices, and systems sufficiently large for classical simulation to be intractable. We use 86 molecular systems to demonstrate that the use of the Bravyi-Kitaev transformation is typically at least approximately as efficient as the canonical Jordan-Wigner transformation, and results in substantially reduced gate count estimates when performing limited circuit optimisations.Comment: 46 pages, 11 figure

    Modelling and experimental investigation of Nb2O5 as a high-rate battery anode material

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    Modelling and understanding the battery electrochemical performance at high rates is a great challenge. Known for its fast rate and good cyclability, niobium pentoxide (Nb2O5) is a promising anode material for lithium-ion batteries and is specifically modelled and investigated in this work. Commercially sourced Nb2O5 was characterised using scanning electron microscopy, X-ray diffraction, and micro-computed tomography. The Nb2O5 material was found to contain large rod- and ball-like polycrystalline particles of tens of microns in size and have mixed T-Nb2O5 and H-Nb2O5 phases. The electrochemical performance of the material after ball milling was tested via cyclic voltammetry and constant-current cycling at different C-rates up to 50C (10,000 mA g−1). The material achieved a similar charge capacity (143 mAh g−1) to T-Nb2O5 at 0.5C and this capacity could be retained by more than 55% when C-rate was increased to 10C. The experimental results were used to support the development of the Doyle-Fuller-Newman electrochemical model for Nb2O5. By model parameterization, the reference exchange-current density and solid-state diffusivity of the present Nb2O5 were estimated to be 9.6 × 10−4 A m−2 and 6.2 × 10−14 m2 s−1, respectively. The model achieved accurate prediction of the battery performance up to currents of 5C with the obtained constant properties. However, the properties of Nb2O5 were found to be rate-dependent at higher C-rates when good agreements between the model and experiment were maintained. The decrease of the two properties at 10−50C revealed that there was a change of dominant charge storage mechanism from diffusion-controlled lithium insertion to capacitive effects, which was experimentally observed in the cyclic voltammetry

    Recent advances in acoustic diagnostics for electrochemical power systems

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    Over the last decade, acoustic methods, such as acoustic emission and ultrasonic testing, have been increasingly deployed for process diagnostics and health monitoring of electrochemical power devices including batteries, fuel cells, and water electrolysers. These acoustic are non-invasive, highly sensitive, and low cost, while also providing a high level of spatial and temporal resolution, and practicality. The application of these tools in electrochemical devices is based on identifying changes in acoustic signals due to physical, structural, and electrochemical properties change within the material which are then correlated to critical processes and the health status of the devices. This review discusses recent progress in the use of acoustic methods for process and health-monitoring of major electrochemical energy conversion and storage devices. First, the fundamental concepts and principles of acoustic emission and ultrasonic testing are introduced, followed by a discussion of the range of electrochemical energy conversion and storage systems, and how acoustic techniques are being used to study relevant materials and devices. Conclusions and future perspectives highlighting some of the unique challenges and potential commercial and academic applications of the devices are also discussed. It is expected that, with further developments, acoustic techniques will form a key part of the suite of diagnostic techniques routinely used to monitor electrochemical devices across various processes including fabrication, on-board maintenance, post-mortem examination and second life or recycle decision support to aid the deployment of these devices in increasingly demanding applications

    Sustainability in Turbulent Times: Lessons from the Nexus Network for supporting transdisciplinary research

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    This is the final version. Available from the Nexus Network via the link in this recordEconomic and Social Research Council (ESRC
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