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Assimilation of experimental data to create a quantitatively-accurate reduced order thermoacoustic model
No full textWe combine a thermoacoustic experiment with a thermoacoustic reduced order model using Bayesian inference to accurately learn the parameters of the model, rendering it predictive. The experiment is a vertical Rijke tube containing an electric heater. The heater drives a base flow via natural convection, and thermoacoustic oscillations via velocity-driven heat release fluctuations. The decay rates and frequencies of these oscillations are measured every few seconds by acoustically forcing the system via a loudspeaker placed at the bottom of the tube. More than 320,000 temperature measurements are used to compute state and parameters of the base flow model using the Ensemble Kalman Filter. A wave-based network model is then used to describe the acoustics inside the tube. We balance momentum and energy at the boundary between two adjacent elements, and model the viscous and thermal dissipation mechanisms in the boundary layer and at the heater and thermocouple locations. Finally, we tune the parameters of two different thermoacoustic models on an experimental dataset that comprises more than 40,000 experiments. This study shows that, with thorough Bayesian inference, a qualitative model can become quantitatively accurate, without overfitting, as long as it contains the most influencial physical phenomena
Design and Evaluation of Magnetic Hall Effect Tactile Sensors for Use in Sensorized Splints.
No full textSplinting techniques are widely used in medicine to inhibit the movement of arthritic joints. Studies into the effectiveness of splinting as a method of pain reduction have generally yielded positive results, however, no significant difference has been found in clinical outcomes between splinting types. Tactile sensing has shown great promise for the integration into splinting devices and may offer further information into applied forces to find the most effective methods of splinting. Hall effect-based tactile sensors are of particular interest in this application owing to their low-cost, small size, and high robustness. One complexity of the sensors is the relationship between the elastomer geometry and the measurement range. This paper investigates the design parameters of Hall effect tactile sensors for use in hand splinting. Finite element simulations are used to locate the areas in which sensitivity is high in order to optimise the deflection range of the sensor. Further simulations then investigate the mechanical response and force ranges of the elastomer layer under loading which are validated with experimental data. A 4 mm radius, 3 mm-thick sensor is identified as meeting defined sensing requirements for range and sensitivity. A prototype sensor is produced which exhibits a pressure range of 45 kPa normal and 6 kPa shear. A proof of principle prototype demonstrates how this can be integrated to form an instrumented splint with multi-axis sensing capability and has the potential to inform clinical practice for improved splinting
Deterioration and Cracking in Reinforced Concrete Bridges
No full textReinforced concrete structures are subjected to several sources of deterioration that can cause a progressive reduction in performance. Among the existing infrastructure typologies, reinforced concrete half-joint bridges are particularly critical. This common structural configuration is characterised by a reduction in depth at the supports. The underside of the full-depth section does not benefit from support confinement in the anchorage zone of the longitudinal tensile reinforcement. Moreover, leakage of contaminated water often causes corrosion of the internal steel reinforcement and cracking of the concrete cover. Thus, half-joints are particularly vulnerable to bond degradation due to corrosion and cracking. To develop an improved understanding of deterioration in reinforced concrete, and half-joints in particular, three experimental programmes were carried out. The first investigation consisted of accelerated corrosion and concentric pull-out testing on unconfined concrete specimens. It was found that bond degradation only occurred where corrosion products caused expansive pressure, splitting cracks and a progressive loss of rib interlock. The reduction in bond depended upon the widths of the cracks, irrespective of the levels of corrosion. Surface crack widths resulted in better indicators of corrosion-induced bond degradation than conventional measures of corrosion such as mass loss or attack penetration. In the second investigation, a novel bond test set-up was developed to remove the parasitic effect of external confinement from the support reactions. The new geometry was adopted to study the effects of internal confinement on bond. The results showed that the dependence of anchorage capacity upon the concrete cover distance was not monotonic in the presence of confining reinforcement. Within a range of optimum cover-to-diameter ratios, small splitting cracks activated the transverse reinforcement and led to a bond strength uplift. In the third investigation, half-joint beams were tested in three-point bending to study the consequences of anchorage degradation on the overall behaviour of the component. Analytical predictions based on the lower bound theorem of plasticity were found to be overly conservative and did not capture the behaviour observed experimentally. This was attributed to a combination of local effects of greater anchorage capacity than predicted and global effects relating to alternative load-paths not taken into account by the predictive models. It was concluded that local deterioration led to a premature local failure of the half-joints, whilst the rest of the structural component was far from its ultimate behaviour and little redistribution had occurred. These conditions undermine the assumptions that underpin plasticity-based models for new design, thus reducing their accuracy when used for the assessment of existing structures in the presence of deterioration. The findings of this research contribute to the development of an effective assessment approach that correlates visual and measurable parameters on the outer surface of the concrete (e.g. crack widths), deterioration processes hidden inside the structure (e.g. bond degradation) and their structural consequences (e.g. overall strength reduction). Improved assessments could lead to enhanced asset management strategies that would reduce the safety risks, maintenance costs and environmental footprint of the infrastructure network
Erratum: Strongly coloured thiocyanate frameworks with perovskite-analogue structures (Chem. Sci. (2019) 10 (793-801) DOI: 10.1039/C8SC04082F)
No full textThe Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers
Multifunctional, Room-Temperature Processable, Heterogeneous Organic Passivation Layer for Oxide Semiconductor Thin-Film Transistors
No full textIn recent decades, oxide thin-film transistors (TFTs) have attracted a great deal of attention as a promising technology in terms of next-generation electronics due to their outstanding electrical performance. However, achieving robust electrical characteristics under various environments is a crucial challenge for successful realization of oxide-based electronic applications. To resolve the limitation, we propose a highly flexible and reliable heterogeneous organic passivation layer composed of stacked parylene-C and diketopyrrolopyrrole-polymer films for improving stability of oxide TFTs under various environments and mechanical stress. The presented multifunctional heterogeneous organic (MHO) passivation leads to high-performance oxide TFTs by: (1) improving their electrical characteristics, (2) protecting them from external reactive molecules, and (3) blocking light exposure to the oxide layer. As a result, oxide TFTs with MHO passivation exhibit outstanding stability in ambient air as well as under light illumination: the threshold voltage shift of the device is almost 0 V under severe negative bias illumination stress condition (white light of 5700 lx, gate voltage of -20 V, and drain voltage of 10.1 V for 20 »000 s). Furthermore, since the MHO passivation layer exhibits high mechanical stability at a bending radius of ≤5 mm and can be deposited at room temperature, this technique is expected to be useful in the fabrication of flexible/wearable devices
A biohybrid synapse with neurotransmitter-mediated plasticity
No full textBrain-inspired computing paradigms have led to substantial advances in the automation of visual and linguistic tasks by emulating the distributed information processing of biological systems1. The similarity between artificial neural networks (ANNs) and biological systems has inspired ANN implementation in biomedical interfaces including prosthetics2 and brain-machine interfaces3. While promising, these implementations rely on software to run ANN algorithms. Ultimately, it is desirable to build hardware ANNs4,5 that can both directly interface with living tissue and adapt based on biofeedback6,7. The first essential step towards biologically integrated neuromorphic systems is to achieve synaptic conditioning based on biochemical signalling activity. Here, we directly couple an organic neuromorphic device with dopaminergic cells to constitute a biohybrid synapse with neurotransmitter-mediated synaptic plasticity. By mimicking the dopamine recycling machinery of the synaptic cleft, we demonstrate both long-term conditioning and recovery of the synaptic weight, paving the way towards combining artificial neuromorphic systems with biological neural networks
Maximising discharge burnup in an open cycle molten salt reactor
No full textThis paper discusses work done to find an estimate of the maximum achievable discharge burnup in an open cycle molten salt reactor (MSR). An in-development deterministic code (WIMS11) is used to create a model of a simple generic MSR, and the methodology employed is discussed. Some experimentation is done with regards to the internal set-up of the 'unit cells' within the core, which shows there is a strong link between this geometry and the achievable burnup. Work is done to quantify the effects of removing volatile fission products and implementing a two-batch refuelling scheme. Finally, an optimisation process is carried out whereby the optimal proportion of graphite moderator within the core is found which balances power across the regions while maximising discharge burnup. Two fuels are tested, one which carries only 235U and 238U, and another which also carries 232Th. It is found that the maximum achievable discharge burnup is approximately 155 MWd/kg, which is considerably higher than modern PWRs, despite a lower enrichment and only two batches of fuel being used
A backward Itô–Ventzell formula with an application to stochastic interpolation
No full textThis Note and its extended version [7] present a novel backward Itô–Ventzell formula and an extension of the Aleeksev–Gröbner interpolating formula to stochastic flows. We also present some natural spectral conditions that yield direct and simple proofs of time uniform estimates of the difference between the two stochastic flows when their drift and diffusion functions are not the same
Breaking the Screen: Interaction Across Touchscreen Boundaries in Virtual Reality for Mobile Knowledge Workers.
No full textHigh performance, 3D-hierarchical CoS<inf>2</inf>/CoSe@C nanohybrid as an efficient electrocatalyst for hydrogen evolution reaction
No full textElectrolysis, driven by renewables, is ideally a direct and clean route to generate the hydrogen. However, for the efficient H2 generation designing active, stable and low cost electrocatalyst system to replace expensive Pt is of paramount importance. Here, a hetero-structured system composed of CoS2 and CoSe nanostructures on carbon matrix (CoS2/CoSe@C) is proposed as an active electrocatalyst for hydrogen evolution reaction (HER) in acid medium. The composition of sulfur and selenium in the derived CoS2/CoSe@C electrocatalyst is analytically controlled for the enhanced HER performance. The prepared electrocatalyst offers the low overpotential of 164 mV at the current density of 10 mA cm−2 with a small Tafel slope of 42 mV dec−1 as a result of proper synergy between the active components CoS2 and CoSe. Moreover, the interconnected network in the carbon matrix of CoS2/CoSe@C provides better conductivity ensured by adequate contact area between the electrocatalyst and electrolyte. Besides the convincing electrochemical activity, catalyst demonstrates the good stability for at least 10 h. This work highlights importance of composite materials for HER via synchronizing catalytically active materials (Ni, Co, Mo) and highly conductive supports (CNT, C, rGO)