27 research outputs found

    Heat pipe based battery thermal management: Evaluating the potential of two novel battery pack integrations

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    © 2021 The Author(s). Lithium-ion batteries are widely used in high power applications and, with more industries focusing on the electrification of their processes, the need for an effective battery thermal management system is growing. The use of a thermal management system serves multiple purposes such as safeguarding the battery from catastrophic thermal runaway and increasing the lifespan of the battery pack. In the present paper, the thermal management of a sixteen-cell battery module, by two different configurations of a heat pipe based thermal management system, is investigated experimentally. In the first configuration, the module is fixed on top of a single horizontal ‘heat mat’. The second configuration consists of the module sandwiched between two vertical heat mats. The comparison of the cooling performances of these two configurations showed their ability to efficiently absorb the heat generated by the cells and maintain their temperatures close to the ideal operating range. During representative cycles of operation, the maximum cell temperature was kept below 28.5 °C and 24.5 °C for the horizontal and vertical heat mat configurations respectively. The cell temperature uniformity across the module stays in a +/-1 °C range, which will reduce cell voltage imbalance, loss of useable capacity and non-uniform ageing. The maximum temperature difference across the height of the cells was 6 °C for the horizontal configuration and 2 °C for the vertical one. The second part of this paper compares the heat removed in both configurations when loaded with a quasi-steady-state heat generation. The third study uses a faster (6C) charge rate during a representative cycle and shows that the maximum temperature stays below 30 °C and 28 °C for the horizontal and vertical configurations respectively.Innovative UK (Grant no. 3941/133371)

    Design of a high-performance optical tweezer for nanoparticle trapping

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    Integrated optical nanotweezers offer a novel paradigm for optical trapping, as their ability to confine light at the nanoscale leads to extremely high gradient forces. To date, nanotweezers have been realized either as photonic crystal or as plasmonic nanocavities. Here, we propose a nanotweezer device based on a hybrid photonic/plasmonic cavity with the goal of achieving a very high quality factor-to-mode volume (Q/V) ratio. The structure includes a 1D photonic crystal dielectric cavity vertically coupled to a bowtie nanoantenna. A very high Q/V ~ 107 (λ/n)−3 with a resonance transmission T = 29 % at λR = 1381.1 nm has been calculated by 3D finite element method, affording strong light–matter interaction and making the hybrid cavity suitable for optical trapping. A maximum optical force F = −4.4 pN, high values of stability S = 30 and optical stiffness k = 90 pN/nm W have been obtained with an input power Pin = 1 mW, for a polystyrene nanoparticle with a diameter of 40 nm. This performance confirms the high efficiency of the optical nanotweezer and its potential for trapping living matter at the nanoscale, such as viruses, proteins and small bacteria

    Variability in the analysis of a single neuroimaging dataset by many teams

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    Data analysis workflows in many scientific domains have become increasingly complex and flexible. To assess the impact of this flexibility on functional magnetic resonance imaging (fMRI) results, the same dataset was independently analyzed by 70 teams, testing nine ex-ante hypotheses. The flexibility of analytic approaches is exemplified by the fact that no two teams chose identical workflows to analyze the data. This flexibility resulted in sizeable variation in hypothesis test results, even for teams whose statistical maps were highly correlated at intermediate stages of their analysis pipeline. Variation in reported results was related to several aspects of analysis methodology. Importantly, meta-analytic approaches that aggregated information across teams yielded significant consensus in activated regions across teams. Furthermore, prediction markets of researchers in the field revealed an overestimation of the likelihood of significant findings, even by researchers with direct knowledge of the dataset. Our findings show that analytic flexibility can have substantial effects on scientific conclusions, and demonstrate factors related to variability in fMRI. The results emphasize the importance of validating and sharing complex analysis workflows, and demonstrate the need for multiple analyses of the same data. Potential approaches to mitigate issues related to analytical variability are discussed

    Variability in the analysis of a single neuroimaging dataset by many teams

    Get PDF
    Data analysis workflows in many scientific domains have become increasingly complex and flexible. To assess the impact of this flexibility on functional magnetic resonance imaging (fMRI) results, the same dataset was independently analyzed by 70 teams, testing nine ex-ante hypotheses. The flexibility of analytic approaches is exemplified by the fact that no two teams chose identical workflows to analyze the data. This flexibility resulted in sizeable variation in hypothesis test results, even for teams whose statistical maps were highly correlated at intermediate stages of their analysis pipeline. Variation in reported results was related to several aspects of analysis methodology. Importantly, meta-analytic approaches that aggregated information across teams yielded significant consensus in activated regions across teams. Furthermore, prediction markets of researchers in the field revealed an overestimation of the likelihood of significant findings, even by researchers with direct knowledge of the dataset. Our findings show that analytic flexibility can have substantial effects on scientific conclusions, and demonstrate factors related to variability in fMRI. The results emphasize the importance of validating and sharing complex analysis workflows, and demonstrate the need for multiple analyses of the same data. Potential approaches to mitigate issues related to analytical variability are discussed
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