MRC Laboratory of Molecular Biology
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Low complexity DSP for high speed optical access networking
No full textA novel low-cost and energy-efficient approach for reaching 40 Gb/s signals is proposed for cost-sensitive optical access networks. Our proposed design is constituted of an innovative low-complex high-performance digital signal processing (DSP) architecture for pulse amplitude modulation (PAM-4), reuses existing commercial cost-effective 10-G components and eliminates the need of a power-hungry radio frequency (RF) component in the transmitter. Using a multi-functional 17-tap reconfigurable adaptive Volterra-based nonlinear equalizer with noise suppression, significant improvement in receiver optical power sensitivity is achieved. Results show that over 30 km of single-mode fiber (SMF) a link power budget of 33 dB is feasible at a bit-error-rate (BER) threshold of 10-3
A Case Study on the Application of Energy Tunnels in Sydney, Australia
No full textShallow geothermal energy systems are known to efficiently provide renewable energy for heating and cooling purposes. Energy geo-structures constitute a relatively recent application of these systems where the use of traditional purpose-made boreholes or trenches as ground heat exchangers (GHEs) is minimised or avoided by incorporating geothermal piping in underground structural elements such as piles, retaining walls and tunnels. This study explores the application of energy tunnels in the M4 – M5 Link project in New South Wales, Australia, which includes the construction of twin motorway tunnels of around 7.5 km in length for up to 4 lanes of traffic. The presented work examines this premise in detail by utilising advanced numerical modelling approaches and high-performance computing applications to investigate the long-term applicability of energy tunnels for this case study. The results indicate that thermally activating the entire tunnel could provide up to about 38.6 GWh per year for heating and cooling. A number of pipe configurations are also investigated, suggesting that placing the pipes only on either side of lining of the tunnel (as opposite to top or bottom) can result in a better thermal performance due to thermal interference and in this case provide up to about 17.5 GWh per year
Nano-fe<inf>3</inf>o<inf>4</inf>/carbon nanotubes composites by one-pot microwave solvothermal method for supercapacitor applications
No full textCarbon nanotubes (CNTs) are being increasingly studied as electrode materials for su-percapacitors (SCs) due to their high electronic conductivity and chemical and mechanical stability. However, their energy density and specific capacitance have not reached the commercial stage due to their electrostatic charge storage system via a non-faradic mechanism. Moreover, magnetite (Fe3O4) exhibits higher specific capacitance originating from its pseudocapacitive behaviour, while it has irreversible volume expansion during cycling. Therefore, a very interesting and facile strategy to arrive at better performance and stability is to integrate CNTs and Fe3O4. In this study, we demonstrate the microwave-solvothermal process for the synthesis of Fe3O4 nanoparticles uniformly grown on a CNT composite as an electrode for SCs. The synthesized Fe3O4/CNT composite delivers a reversible capacitance of 187.1 F/g at 1 A/g, superior rate capability by maintaining 61.6% of 10 A/g (vs. 1 A/g), and cycling stability of 80.2% after 1000 cycles at 1 A/g
Author Correction: Optoelectronic mixing with high-frequency graphene transistors.
No full textGraphene is ideally suited for optoelectronics. It offers absorption at telecom wavelengths, high-frequency operation and CMOS-compatibility. We show how high speed optoelectronic mixing can be achieved with high frequency (~20 GHz bandwidth) graphene field effect transistors (GFETs)
Two-Dimensional Gallium Oxide Monolayer for Gas-Sensing Application
No full textA two-dimensional (2D) Ga2O3monolayer with an asymmetric quintuple-layer configuration was reported as a novel 2D material with excellent stability and strain tunability. This unusual asymmetrical structure opens up new possibilities for improving the selectivity and sensitivity of gas sensors by using selected surface orientations. In this study, the surface adsorptions of nine molecular gases, namely, O2, CO2, CO, SO2, NO2, H2S, NO, NH3, and H2O, on the 2D Ga2O3monolayer are systematically investigated through first-principles calculations. The intrinsic dipole of the system leads to different adsorption energies and changes in the electronic structures between the top- and bottom-surface adsorptions. Analyses of electronic structures and charge transport calculations indicate a potential application of the 2D Ga2O3monolayer as a room-temperature NO gas-sensing device with high sensitivity and tunable adsorption energy using plenary strain-induced lattice distortion
Minimising embodied carbon in reinforced concrete beams
No full textThe construction industry has received attention due to its significant contribution to global carbon emissions. In this paper, conventional design and construction practices of reinforced concrete beams are scrutinised to explore the potential for reductions in embodied carbon. For a given set of design criteria, a family of discrete beam designs which have different geometries and corresponding reinforcements were developed to identify those with minimum embodied carbon. Two algorithms for shape optimisation were developed, one to identify the geometry of the theoretical optimum design, and another considering technical and construction feasibility. Prismatic beams were also optimised exploring alternative designs with different depths and widths along with the required reinforcements, for a reasonable comparison. Several cases were studied to understand the effect of different design parameters. Different design criteria suggested different geometries to minimise embodied carbon, even if the design span was the same. The importance of minimising web width was seen throughout the analysis. The expected deflection of each design was also estimated to understand the effect of optimisation on serviceability performance and found to be satisfactory in all the cases. Embodied carbon of beams can be reduced by up to 38% by optimising prismatic beams compared with conventional designs. Further savings up to 8% are possible with a feasible shape optimised design compared with optimised prismatic beams
Molecular dynamics simulations of ultrathin PMMA films
No full textThe mechanical properties of an ultrathin film made from a thermoplastic differ from the bulk due to the presence of the free surface. Here, molecular dynamics simulations are used to explore the thickness dependence of uniaxial and equi-biaxial tensile responses of polymethyl methacrylate (PMMA) films. The sensitivity of deformation response to temperature, molecular weight and the degree of side-branching is determined. We find that the tensile failure strain decreases with decreasing film thickness, temperature, and with decreasing molecular weight. The degree of side-branching plays a secondary role in dictating the tensile response. Failure is by the initiation of voids at the free surface, followed by the expansion of the voids in the thickness direction. Recent solid−state nanofoaming experiments and models suggest that the attainable porosity of nanofoams is less than that of macro−scale foams due to the reduced ductility of the cell walls of the nanofoam. Our results provide a physical explanation for this observation
Anisotropic Carbon Nanotube Structures with High Aspect Ratio Nanopores for Li-Ion Battery Anodes
No full textTechnological advances in membrane technology, catalysis, and electrochemical energy storage require the fabrication of controlled pore structures at ever smaller length scales. It is therefore important to develop processes allowing for the fabrication of materials with controlled submicron porous structures. We propose a combination of colloidal lithography and chemical vapor deposition of carbon nanotubes to create continuous straight pores with diameters down to 100 nm in structures with thicknesses of more than 300 μm. These structures offer unique features, including continuous and parallel pores with aspect ratios in excess of 3000, a low pore tortuosity, good electrical conductivity, and electrochemical stability. We demonstrate that these structures can be used in Li-ion batteries by coating the carbon nanotubes with Si as an active anode material
OESDs in an on-road study of semi-automated vehicle to human driver handovers
No full textDesign of appropriate interaction and human–machine interfaces for the handover of control between vehicle automation and human driver is critical to the success of automated vehicles. Problems in this interfacing between the vehicle and driver have led, in some cases, to collisions and fatalities. In this project, Operator Event Sequence Diagrams (OESDs) were used to design the handover activities to and from vehicle automation. Previous work undertaken in driving simulators has shown that the OESDs can be used to anticipate the likely activities of drivers during the handover of vehicle control. Three such studies showed that there was a strong correlation between the activities drivers represented in OESDs and those observed from videos of drivers in the handover process, in driving simulators. For the current study, OESDs were constructed during the design of the interaction and interfaces for the handover of control to and from vehicle automation. Videos of drivers during the handover were taken on motorways in the UK and compared with the predictions from the OESDs. As before, there were strong correlations between those activities anticipated in the OESDs and those observed during the handover of vehicle control from automation to the human driver. This means that OESDs can be used with some confidence as part of the vehicle automation design process, although validity generalisation remains an important goal for future research
Mobility degradation in 4H-SiC MOSFETs and interfacial formation of carbon clusters
No full textWe describe a detailed atomic model of the SiC/SiO2 interface states due to carbon clusters which lower the field effect mobility of SiC below its Hall effect value, due to the oxidation process. The carbon clusters are on the SiO2 side. We show for the first time that carbon clusters containing a mixture of sp2 and sp3 sites explain the results, with these sp2 sites forming small sub-clusters to maintain a large local band gap