MRC Laboratory of Molecular Biology
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Tristable properties and limit point behaviour in electrostatically actuated initially curved coupled micro beams
No full textA limit point behaviour of a metastructure, composed of two double clamped, initially curved beams, coupled via a rigid truss at their respective centres, is studied when subjected to a distributed electrostatic load. The analysis is based on a reduced order (RO) model, resulting from Galerkin's decomposition, with symmetric buckling modes used as the base functions. To better understand the behaviour of the structure, the electrostatic analysis is preceded by a study of the model under “mechanical”, displacement-independent, load, allowing validation against a finite elements (FE) model, which served as proving ground for the RO model. In addition, results obtained by the RO model are compared with those extracted via finite differences (FD) solutions, facilitating the usage of the latter as the reference in the electrostatic, displacement-dependent, analysis. To accommodate for winding equilibrium paths, all solutions employed the implicit arc-length “Riks” method. The analysis has produced complicated equilibrium paths, which necessitated a corresponding local stability analysis, conducted using the energy method, allowing for limit point characterisation. The analyses have shown that the double beam metastructure is able to possess bistable and tristable properties, usually found in highly complex structures, which can be cumbersome for design and miniaturisation, provided that it meets certain geometrical parameters. Several variations of tristability are disclosed in the study, hitherto unknown, providing insight to the complexity of the structure. The analysis indicates that a model with at least three degrees-of-freedom (DOF) is needed to predict the various critical thresholds with reasonable errors. In so doing, the model can be used for static characterisation and design of various applications, where a simple structure, possessing tristable properties, is required
Magnetization Loss Characteristics in Superconducting Conductor on Round Core Cables with a Copper Former
No full textThe High Temperature Superconducting (HTS) Conductor on Round Core (CORC) cables have been widely utilized to fabricate various superconducting applications for power transmission, fusion, and magnets with high current density. Understanding the AC loss behavior of CORC cables during the cable design process is essential for analyzing its electromagnetic performance and evaluating its future industry potential. The aim of our research is to investigate the AC loss dependence caused by the magnitude and frequency of applied external variations to the magnetic field. This paper describes the simulation models of HTS CORC cables based on the finite-element method (FEM) by using an H-formulation in a commercial software named COMSOL Multiphysics. Three-dimensional (3-D) CORC models, with three HTS tapes wound around each layer, were built and analyzed. The 3-D CORC models, built using the FEM method, were then verified with published experimental results. AC losses dissipated in the CORC cables, resulting from applied external varying magnetic field, were calculated and examined
Data-driven secure, resilient and sustainable supply chains: gaps, opportunities, and a new generalised data sharing and data monetisation framework
No full textThe increasing exposure of global supply chains to severe disruptions such as the ones related to the COVID-19 pandemic, clearly demonstrated the need for novel data-driven risk management paradigms that monetise data from internal and external stakeholders to support supply chain security, resilience, and sustainability. We first motivate the challenges that supply chains are facing under the new realities. We then provide a critical taxonomy of the relevant literature and identify gaps which include: (i) the impact of security on supply chain operations; (ii) cost effective resiliency strategies and practices; and (iii) the social and labour dimensions of sustainability. We then propose a new generalised framework that encompasses all the identified challenges, gaps in literature and in practice, and opportunities in supply chain management research. The proposed framework is validated through a real-world case study of the organic food supply chain. This validation further highlights the need for data-driven digital technologies that enable data collection and management, secure storage and effective data processing towards data monetisation for supply chain security, cost-competitive resilience, and sustainability across end-to-end operations
Experiments and analysis of corona inception voltage under combined AC-DC voltages at various air pressure and humidity in rod to plane electrodes
No full textAs the effect of climate plays a significant role in corona discharge under combined voltages, the variation of corona inception voltage with different air pressure and humidities is studied. An experimental platform, based on a rod-to-plane electrode, is constructed with adjustable air pressure from 0.06 MPa to 0.10 MPa and with a relative humidity (RH) from 20% to 90%. The variation of ultraviolet (UV) photon count and corona inception voltage is obtained at various climate conditions under different applied voltages: the single AC, single DC, and combined AC-DC. It turns out that all the corona inception voltages decline with the drop of air pressure and the rise of humidity under different applied voltages. The influence between different voltages primarily relies on space charge, as more AC components make it easier to accumulate positive ions. The existence of AC makes ions move forward and backward while the existence of DC dominates the polarity of corona and general drift directions. At last the fitting formula of hybrid corona inception voltage combining air pressure and relative humidity is given
Emerging light-emitting diodes for next-generation data communications
No full textThe continuing development of consumer electronics, mobile communications and advanced computing technologies has led to a rapid growth in data traffic, creating challenges for the communications industry. Light-emitting diode (LED)-based communication links are of potential use in both free space and optical interconnect applications, and LEDs based on emerging semiconductor materials, which can offer tunable optoelectronics properties and solution-processable manufacturing, are of particular interest in the development of next-generation data communications. Here we review the development of emerging LED materials—organic semiconductors, colloidal quantum dots and metal halide perovskites—for use in optical communications. We examine efforts to improve the modulation performance and device efficiency of these LEDs, and consider potential applications in on-chip interconnects and light fidelity (Li-Fi). We also explore the challenges that exist in developing practical high-speed LED-based data communication systems
Snap-back free 3.3kV RC-IGBT with enhanced safe operating area
No full textIn this paper we present a snap-back free 3.3kV, 75A Reverse Conducting IGBT (RC-IGBT) with improved Reverse Bias (RBSOA) and Short-Circuit (SCSOA) Safe Operating Areas. The device employs floating N+ regions under the gate BUSBARs to locally reduce hole concentration and uses segmented N+ Anode regions to minimise the reverse recovery losses. The device architecture was conceived on extensive TCAD modelling and a DOE approach. The best design variants have been manufactured, tested and used for extensive analysis of key device trade-offs
Analysis on the effect of superconductor layer thick-ness on the AC loss of Conductor on Round Core (CORC) cables
No full textSuperconducting Conductor on Round Core (CORC) cables fab-ricated from high temperature superconducting (HTS) tapes are capable of carrying enormous electrical current density, to be widely used in a variety of superconducting applications such as power transmission, fusion, and magnetic resonance imaging (MRI) [1]. However, the AC losses induced in the superconduct-ing tapes under alternating current or magnetic field generate heat dissipation which can decrease the overall electric power ef-ficiency [2]. Therefore, it is essential to analyze the AC loss be-havior of CORC cables as well as consider methods to reduce it. This paper presents an AC loss study of CORC cables with sev-eral different superconducting layer thicknesses. The CORC ca-ble simulation model is built in a commercial software named COMSOL Multiphysics based on the finite-element method (FEM) solved by the three-dimensional (3-D) H-formulation. By implementing FEM simulations, the cases of increasing the de-gree of freedom of superconducting layers have been considered, and the AC losses of a single layer CORC cable with three tapes mounted around the core have been calculated and analyzed for different layer thicknesses. Simulation results are verified with experimental results measured in previous literature
Achieving an Interference Fit Between Two Rings During Composite Ring Rolling
No full textComposite ring rolling could bring substantial material, cost, and energy savings and allow for lighter weight components, by joining concentric rings with different material properties. For there to be any possibility of achieving a material bond, an interference fit between the rings must be maintained. In this paper, a force equilibrium-based model is introduced to predict when such a fit is possible. This model, for radial composite rolling, predicts a limit to the flow stress of the inner ring relative to the outer ring, suggesting a maximum ratio of about 160%. It also shows that the inner tool’s diameter must often be significantly smaller than the outer tool’s. The model is tested in four composite ring rolling experiments with two grades of Aluminium alloy, 1050 and 6063, and different tool sizes. An interference fit was achieved in two cases: (1) when the inner ring is Al 1050 (flow stress 52% of the outer ring); and (2) when the two rings are both Al 6063 and the inner tool diameter was 39% of the outer tool. It was not achieved when (1) the materials were reversed nor when (2) the inner tool increased to 59% of the outer tool diameter. These outcomes were all predicted by the model, a potentially valuable new guide to designing composite ring rolling processes
Parameter Optimisation for Ultra-Wideband Optical Networks in the Presence of Stimulated Raman Scattering Effect
No full textThis paper studies the effects of channel launch power and topology parameters on performance for ultra-wideband optical networks in the presence of stimulated Raman scattering (SRS). Results exhibit significant throughput improvements for optimised per-channel launch power allocation over conventional uniform power allocation. Furthermore, the impact of network structural features on performance is investigated and a significant increase in throughput and a reduction in fibre installation cost are achieved by optimising network topology for two real world core networks