MRC Laboratory of Molecular Biology
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Erratum: Assessing the acceptability of a text messaging service and smartphone app to support patient adherence to medications prescribed for high blood pressure: A pilot study (Pilot and Feasibility Studies (2020) 6 (134) DOI: 10.1186/s40814-020-00666-2)
No full textFollowing publication of the original article [1], the authors reported an error in the name of the fourth author. The surname should be Brimicombe. The original article has been updated
Electromagnetic and levitation characteristics of a high-temperature superconducting bulk above an electromagnet guideway
No full textAn electromagnet guideway unit (EMGU) that can form an electromagnet guideway (EMG) with only a small gap, or even no gap, between multiple EMGUs was designed. The magnetic characteristics of such EMGU(s), including the homogeneity of the magnetic field along the EMGU(s) and the transverse magnetic field distribution were first investigated. As expected, the EMGU(s) can provide a homogeneous magnetic field in order to levitate bulk superconductors. Simulation results from an EMGU model implemented in COMSOL Multiphysics were verified using experimentally measured data, which indicated the established model can be used for further study and analysis. Next, the levitation characteristics of a high-temperature superconducting (HTS) bulk above the EMGU, including the levitation force acting on HTS bulk due to its interaction with the EMGU, as well as the stability of the bulk when experiencing a lateral disturbance and when varying the current of the EMGU, were investigated through experiment and simulation. The behavior of the levitation force during re-magnetization of the EMGU indicated that a larger re-magnetizing current is needed to suppress the internal magnetic field (trapped field) obtained from the premagnetization process, thereby providing a repulsive force to the superconductor. The stability study showed that the HTS maglev system with an EMGU with adjustable current can not only deal with a reduction of the levitation force but can also increase the restoring force when the superconductor is disturbed laterally. Finally, in order to clarify the mechanism of these levitation characteristics, the internal electromagnetic characteristics of the HTS bulk were analyzed using a 2D model
DSP for Optical Transponders
No full textThis chapter outlines the principles of the digital signal processing (digital signalprocessing (DSP)) used in modern optical transceivers. The historic developments that have led to the emergence of DSP being applied in optical transceivers is reviewed, including the high-speed complementary metal oxide semiconductor (complementary metal–oxide–semiconductor (CMOS)) analog to digital converters (analog-to-digital converter (ADC)) that have facilitated the creation of the application-specific integrated circuit (application-specific integrated circuit (ASIC)) which underpins digital coherent transceivers. Following on from this, the mathematics associated with finite impulse response (finite impulse response (FIR)) filters is reviewed, including the Wiener and least-squares design of FIR filters. The mathematics associated with the adaptive multiple-input-multiple-output (multiple-input multiple-output (MIMO)) filter employed in the receiver is also discussed, including derivation of the stochastic descent algorithm based on differentiation with respect to a complex vector. Subsequently, we provide an overview of DSP algorithms, before detailing both those required for equalization and synchronization. Following a summary of error correction used in a digital transceiver, we reflect on the current research trends and future opportunities for DSP in optical transceivers
A wireless electrode-free QCM-D in a multi-resonance mode for volatile organic compounds discrimination
No full textWireless sensor technology is a facile way of realizing low cost and miniaturized device for the detection of the volatile organic compounds (VOCs). A wireless electrodeless quartz crystal microbalance with dissipation (WE-QCM-D) sensor array was developed by using a single sensor working in a multi-resonance mode, which obtained an acoustic spectra of the quartz crystal at four harmonics (6 MHz, 18 MHz, 30 MHz and 42 MHz). Multi-responses (frequency shift, and energy dissipation) of WE-QCM-D sensor array were obtained via a ring-down mode and employed as discrimination factors for VOCs. The gas discrimination capability of the WE-QCM-D sensor array has been tested by coating a 100 μg polyvinylpyrrolidone film on the quartz disc and achieved an optimal recognition rate of 97.5 % with K nearest neighbor algorithm. The results indicate that the single element WE-QCM-D sensor array could be a promising way to realize compact and low-cost VOCs monitoring systems
Transient performance of >10 kv sic igbt with an optimized retrograde p-well
No full textThe impact of different p-well designs upon the transient performance, in particular, the turn-off losses and short-circuit capability, of a >10 kV SiC n-IGBT is assessed. We find that in addition to improved transient performance, a substantial reduction in the depth of p-well implants can be achieved, if an extensively optimized retrograde approach is utilized. A conventional p-well consisting of a uniformly doped deep implant (doping concentration of ~3×1017 cm-3 and depth of >1.5 µm) exhibits considerable turn-off switching losses without offering any short circuit capability. However, an optimized retrograde p-well consisting of a variable doping profile and depth as shallow as 0.7-0.8 µm results in much reduced turn-off losses with excellent short-circuit capability. Shallow implants are desirable to lower the development cost and processing challenges. The retrograde p-well is therefore highly promising for the development of >10 kV class of SiC IGBTs
Machine learning in chemical reaction space
No full textChemical compound space refers to the vast set of all possible chemical compounds, estimated to contain 1060 molecules. While intractable as a whole, modern machine learning (ML) is increasingly capable of accurately predicting molecular properties in important subsets. Here, we therefore engage in the ML-driven study of even larger reaction space. Central to chemistry as a science of transformations, this space contains all possible chemical reactions. As an important basis for ‘reactive’ ML, we establish a first-principles database (Rad-6) containing closed and open-shell organic molecules, along with an associated database of chemical reaction energies (Rad-6-RE). We show that the special topology of reaction spaces, with central hub molecules involved in multiple reactions, requires a modification of existing compound space ML-concepts. Showcased by the application to methane combustion, we demonstrate that the learned reaction energies offer a non-empirical route to rationally extract reduced reaction networks for detailed microkinetic analyses
High fidelity model for self-sustained oscillations in heated jets
No full text© 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. The effect of property modelling on the stability features of heated axisymmetric jets is investigated by comparing the results of unsteady simulations and spatio-temporal Linear Stability Theory (LST) analyses obtained with three different models of Thermodynamic and Transport Properties (TTP). Two of these models are commonly found in the literature and assume respectively constant properties and a Calorically Perfect Gas (CPG) assumption, while the third model is a novel approach for this kind of study as it considers a mixture of gases in Local Thermodynamic and chemical Equilibrium (LTE) accurate up to extreme temperatures. Each model is implemented in a DNS code already used in the literature for jet stability analyses, and the LST computations are carried out in the VKI Extensible Stability and Transition Analysis (VESTA) toolkit. The LST analysis is performed on the steady state obtained from DNS simulations using a Selective Frequency Damping (SFD) method. Results show that the choice of property model has a significant impact on the development of self-sustained oscillations through changes of the absolute region length. Variable properties introduced in the CPG and LTE model have a amplifying effect on absolute instabilities downstream of the inlet. However, the modification of temperature profiles in LTE is found to strongly damp absolute instabilities at high temperatures. Cases with a long enough absolute region are found to support global modes, which are investigated with a Fast Fourier Transform (FFT) method
Experimental demonstration of in-service security monitoring using a quantum modulated signal
No full textWe experimentally demonstrate a method for in-service optical physical layer security monitoring with vacuum-noise sensitivity that can detect a 1% fiber tapping attack at 50km without classical security loopholes
Application of the PISA design model to monopiles embedded in layered soils
No full textThe PISA design model is a procedure for the analysis of monopile foundations for offshore wind turbine applications. This design model has been previously calibrated for homogeneous soils; this paper extends the modelling approach to the analysis of monopiles installed at sites where the soil profile is layered. The paper describes a computational study on monopiles embedded in layered soil configurations comprising selected combinations of soft and stiff clay and sand at a range of relative densities. The study comprises (a) analyses of monopile behaviour using detailed three-dimensional (3D) finite-element analysis, and (b) calculations employing the PISA design model. Results from the 3D analyses are used to explore the various influences that soil layering has on the performance of the monopile. The fidelity of the PISA design model is assessed by comparisons with data obtained from equivalent 3D finite-element analyses, demonstrating a good agreement in most cases. This comparative study demonstrates that the PISA design model can be applied successfully to layered soil configurations, except in certain cases involving combinations of very soft clay and very dense sand
Spectral shortcut in turbulence energy transfer in open channel flow over submerged vegetation
No full textThis study explores the characteristics of the spectral shortcut in the turbulence kinetic energy transfer in experimental open channel flows with the presence of submerged vegetation flow. The vegetation layer was simulated by arrays of rigid vertical cylinders, distributed uniformly in the channel bed. Results indicate that there are dual inertial subranges (ISRs) in the spectral distribution of turbulence energy in the penetration layer, where the Kelvin-Helmholtz (KH) and wake vortices coexist. The lower-frequency and higher-frequency ISRs reflect the energy cascading of the KH and wake-scale vortices, respectively. Spectral shortcut narrows the ISR for the KH vortex and contributes to the ISR for the wake-scale vortices, because such an action transfers a significant amount of turbulent energy directly from the large-scale eddies to the wake-scale vortices. We study the influence of spectral shortcut on energy transfer according to the turbulence kinetic energy budget equation for shear turbulence. The transferred energy is found to account for 58–71% of the shear turbulent energy and contributes considerably to the wake-scale turbulence. The strength of the energy transfer increases with the increase in the vegetation density and the mean bulk velocity and the decrease in the relative submergence