MRC Laboratory of Molecular Biology
CUED - Cambridge University Engineering DepartmentNot a member yet
45551 research outputs found
Sort by
Highly anisotropic electronic and mechanical properties of monolayer and bilayer As<inf>2</inf>S<inf>3</inf>
No full textTwo-dimensional(2D) material with high anisotropy as well as robust stability would inspire significant interest in the new-generation electronic and optomechanical field, especially for directional memories, synaptic, neuromorphic and polarization-sensitive photodetector devices. Recently, 2D As2S3 was successfully exfoliated in experiments (Šiškins et al., 2019) and was demonstrated to be stable in the ambient. Herein, by using first principles method, we further systematically predicted its angular-dependent electronic and mechanical properties. Specifically, the angle-resolved effective mass of carriers, carrier mobility, three dimensional band structure, stress–strain relationships, as well as the angle-dependent mechanical properties are investigated. Our results show that 2D As2S3 owns a high anisotropic nature both electronically and mechanically. We found that, due to the large anisotropic charge distributions, 2D single (bilayer) As2S3 has shown a value of 3.15 (3.32) in Young's modulus ratio along two axes. These values are much greater than the corresponding 2D black phosphorous of 2 (Tao et al., 2015), which is experimentally confirmed the largest one up to date. Our findings provide an valuable avenue to realize the flexible orientation-dependent nano-devices
Fabrication of High Specific Electrical Conductivity and High Ampacity Carbon Nanotube/Copper Composite Wires
No full textA challenge is to integrate Cu with carbon nanotubes (CNTs) and form a free-standing composite wire. This is achieved by first making a CNT filament using high concentration (20 g L−1) CNT dispersion, an acid-free wet spinning process and then by replacing the polymer with copper using heat based polymer decomposition and periodic pulse reverse electroplating. It is demonstrated that indeed the specific conductivity and the current-carrying capability (or ampacity) are increased manifold. The multiwalled CNT (MWCNT)/Cu composite wires developed in this paper have electrical conductivity σ ≈ 5.5 × 10 5 S cm−1. These MWCNT/Cu wires are 2/3rd the weight of bulk Cu wires. Their specific electrical conductivity is σρ ≈ 9.38 ×10 4 S cm2g−1 which is 45% higher than International Annealed Copper Standard Cu. These composite wires have an ampacity of A ≈ 20 × 105 and 4 × 105 A cm−2 for 1.5 and 17 mm gauge length wires, respectively, which is four to six times higher than pure Cu depending on the wire lengths. MWCNTs volume percentage in the MWCNT/Cu wire is about 40%
Embodied Visual Navigation with Automatic Curriculum Learning in Real Environments
No full textWe present NavACL, a method of automatic curriculum learning tailored to the navigation task. NavACL is simple to train and efficiently selects relevant tasks using geometric features. In our experiments, deep reinforcement learning agents trained using NavACL significantly outperform state-of-The-Art agents trained with uniform sampling-the current standard. Furthermore, our agents can navigate through unknown cluttered indoor environments to semantically-specified targets using only RGB images. Obstacle-Avoiding policies and frozen feature networks support transfer to unseen real-world environments, without any modification or retraining requirements. We evaluate our policies in simulation, and in the real world on a ground robot and a quadrotor drone. Videos of real-world results are available in the supplementary material
Experimental investigation of unconfined turbulent premixed bluff-body stabilized flames operated with vapourised liquid fuels
No full textThe structure of turbulent unconfined bluff-body flames of vapourised liquid fuels was investigated at conditions far from and close to blow-off with high-speed (5 kHz) OH-PLIF imaging and 10 Hz CH2O-PLIF imaging. Four different fuels were considered: ethanol, heptane, and two different kerosene blends (a conventional Jet-A and an alcohol-to-jet kerosene, respectively denoted as A2 and C1 following the USA National Jet Fuels Combustion Programme. OH-PLIF images of ethanol flames far from blow-off display a high intensity of OH-LIF signal along the shear layer. In contrast, the OH-LIF signal was evenly distributed throughout the recirculation zone (RZ) of the heptane and kerosene flames. Regardless of the fuel used, close to blow-off the flame becomes shorter with peak OH-LIF signal intensities lying inside the RZ. All four fuels showed a decrease in flame surface density (Σ2D) and broadening of the 2-D curvature PDFs as their blow-off limits were approached. An increase in local turbulent consumption speed was observed in the downstream region as the flames approached blow-off. No significant variation in Σ2D, curvature PDF, and local turbulent consumption speed was observed between the different fuel types. The average CH2O-layer thickness was larger than the computed laminar flame value by a factor of two and six for conditions far from and close to blow-off, respectively. Moreover, heptane and kerosene flames showed more pockets of CH2O-LIF signal within the RZ as compared to ethanol, suggesting that considerably more partially-combusted fluid enters the RZ of the former than the latter. High-speed particle image velocimetry was performed to measure the local velocity fields and place various regions of the flame on the turbulent premixed regime diagram. It was observed that, regardless of fuel type, conditions close to blow-off occupy the same region on the regime diagram. However, the fact that the fuel type results in differences in some structural features near blow-off suggests that flames produced with heavy hydrocarbon fuels involve chemistry effects at blow-off that are not fully characterized by laminar flame properties
A Closed-Form Solution to Estimate Spatially Varying Parameters in Heat and Mass Transport
No full textThis letter presents a closed-form solution to estimate space-dependent transport parameters of a linear one dimensional diffusion-transport-reaction equation. The infinite dimensional problem is approximated by a finite dimensional model by 1) taking a frequency domain approach, 2) linear parameterization of the unknown parameters, and 3) using a semi-discretization. Assuming full state knowledge, the commonly used output error criterion is rewritten as the equation error criterion such that the problem results in linear least squares. The optimum is then given by a closed-form solution, avoiding computational expensive optimization methods. Functioning of the proposed method is illustrated by means of simulation
Self-Healing Thin-Film Transistor Circuits on Flexible Substrates
No full textThin-film transistor circuits on flexible substrates hold major promise for next-generation human–machine interface systems. However, a major bottleneck is the reliability of the interconnect, which is prone to open-circuit faults due to mechanical, electrical, and environmental stresses. Here, self-healing interconnects in thin-film transistor circuits are demonstrated on flexible substrates resulting in the restoration of >99% of the prefault current. The active material for self-healing is a dispersion of conductive particles in an insulating fluid that is contained over the interconnect. Healing is triggered by the electric field that appears in the open gap during the occurrence of the fault. The engineering of the active material is discussed; self-healing circuits are demonstrated and analyzed; and methods to package and integrate the self-healing feature are discussed with the process flow. This work sets a new benchmark for reliable inkjet-printed thin-film transistor circuits on flexible substrates
Comments on: “Carbon emissions and costs associated with subsidizing New York nuclear instead of replacing it with renewables”
No full textWe respond to the paper “Carbon emissions and costs associated with subsidizing New York nuclear instead of replacing it with renewables” (Cebulla and Jacobson, 2018). The paper found that it would be cheaper to build new renewable energy infrastructure than to continue to subsidise existing nuclear power plants via Zero Emission Credits. We identify a possible error in the calculation of the total annual energy produced by these power plants that, if corrected, could invert the paper's central finding regarding cost
2D Material Memristor Devices for Neuromorphic Computing
No full textNeuromorphic computing offers to overcome the shortcomings associated with traditional von Neumann architectures. These suffer from bottlenecks caused by the separation of memory and processing, leading to large latency and high power consumption. One of the leading methods of achieving this is using memristors. The mass development of memristors presents a number of challenging problems which may be addressed through the use of 2D materials which offer a range of unique properties. In this work we explore the different 2D materials which demonstrate potential to be used as memristors. We explore some applications of such memristors and assess the challenges and future directions this area could develop
Corner effects for compression corner shock wave/boundary layer interactions in rectangular channels
No full textA 20 deg compression corner is used to establish a separated oblique shock wave/turbulent boundary layer interaction in a rectangular cross-sectioned wind tunnel with an incoming Mach number of 2.5. An experimental investigation is conducted to establish the influence of separation in the streamwise corners, formed by the intersection of the working-section floor and side walls, on the quasi two-dimensional main interaction and by what mechanism the two regions interact. To investigate this, the streamwise location and size of the corner separations are manipulated and the flowfield is studied using schlieren photography, oil-flow visualisations, pressure sensitive paint, and laser Doppler velocimetry measurements. The results indicate that the size and structure of the primary separation can vary considerably with different streamwise locations of corner separation. Three regimes of corner effects are identified with respect to the primary separation length; a regimes of enhanced streamwise separation length, decreased separation length, and quasi two-dimensional separation. Compression waves and expansion fans generated as a result of the displacement effect of the corner separations appear to be the primary mechanism behind the observed behaviour. These waves propagate from the corner regions and impinge on the primary interaction, modifying the pressure rise and adverse pressure gradient
Evaluating the Epley Canalolith Repositioning Procedure With and Without a Visual Assistive Device
No full textHYPOTHESIS: The primary goal of this study was to examine how accuracy is affected when we employ a guidance device to assist with the execution of the Epley canalolith repositioning procedure. BACKGROUND: Benign paroxysmal positional vertigo is a common cause of vestibular vertigo. Treatment is noninvasive and generally effective when performed correctly. Deficiencies in clinical application result in unnecessary failures in response for those affected. METHODS: Ten participants were each taken through six iterations of the Epley canalolith repositioning procedure. Iterations were divided evenly between those conducted with and without the use of a guidance device. One clinician performed all 60 procedures. Head movements were recorded using motion capture cameras and strategically placed motion tracking markers. RESULTS: Results showed that the guidance device significantly improved the latter phase maneuver accuracy. Rotation error was significantly reduced for hold3 with-device (M = 20.23°, SD = 12.08°) versus without-device (M = 40.13°, SD = 14.62°, p = 0.001). Maximal rotation error during rotation4 of the maneuver demonstrated a similar reduction of error with-device (M = 24.44°, SD = 10.43°) versus without-device (M = 41.36°, SD = 12.89°, p = 0.002). CONCLUSION: A simple visual guidance device can increase the execution accuracy of canalith repositioning procedures. Further research is required to show how such improvements influence treatment efficacy