MRC Laboratory of Molecular Biology
CUED - Cambridge University Engineering DepartmentNot a member yet
45551 research outputs found
Sort by
Perception of perspective in augmented reality head-up displays
No full textAugmented Reality (AR) is emerging fast with a wide range of applications, including automotive AR Head-Up Displays (AR HUD). As a result, there is a growing need to understand human perception of depth in AR. Here, we discuss two user studies on depth perception, in particular on the perspective cue. The first experiment compares the perception of the perspective depth cue (1) in the physical world, (2) on a flat-screen, and (3) on an AR HUD. Our AR HUD setup provided a two-dimensional vertically oriented virtual image projected at a fixed distance. In each setting, participants were asked to estimate the size of a perspective angle. We found that the perception of angle sizes on AR HUD differs from perception in the physical world, but not from a flat-screen. The underestimation of the physical world's angle size compared to the AR HUD and screen setup might explain the egocentric depth underestimation phenomenon in virtual environments. In the second experiment, we compared perception for different graphical representations of angles that are relevant for practical applications. Graphical alterations of angles displayed on a screen resulted in more variation between individuals' angle size estimations. Furthermore, the majority of the participants tended to underestimate the observed angle size in most conditions. Our results suggest that perspective angles on a vertically oriented fixed-depth AR HUD display mimic more accurately the perception of a screen, rather than the perception of the physical 3D environment. On-screen graphical alteration does not help to improve the underestimation in the majority of cases
Design, construction and validation of MATELab: A novel outdoor chamber for investigating occupant-facade interaction
No full textTesting of novel facade technologies with human volunteers is essential for improving occupant interaction with novel dynamic facade systems and to increase satisfaction with its modulation of light, sound, heat and mass transfer between the outdoor and indoor environments. In the past 10 years, there have been noticeable attempts to develop chambers that endeavour to assess the influence of facade technologies on occupant environmental perception and occupant-facade interaction. This paper firstly reviews existing state-of-the-art chambers for occupant-facade interaction and establishes the principal design criteria and performance characteristics required for such facade test chambers. The paper then demonstrates how this information is used to design and construct MATELab, a facade test chamber in Cambridge, UK, devised for capturing occupant environmental perception to, and interaction with, the facade in a realistic, yet sufficiently accurate manner. Finally, results from a preliminary measurement campaign in MATELab are used to validate the experimental setup, in particular its ability to capture high-resolution data for assessing: (i) the influence of facades on Indoor Environmental Quality (IEQ); (ii) occupant environmental perception and interaction with the facade and (iii) do so similarly to typical office spaces. It was found that MATELab can successfully identify the correlations between facade performance and IEQ and that occupant response can be captured with sufficient frequency and in a realistic manner. However, further work is required to improve the experimental setup, in particular, to monitor luminance and direct solar radiation within the indoor space in a non-disruptive, yet experimentally efficient manner
Autonomous Tracking and State Estimation With Generalized Group Lasso
No full textWe address the problem of autonomous tracking and state estimation for marine vessels, autonomous vehicles, and other dynamic signals under a (structured) sparsity assumption. The aim is to improve the tracking and estimation accuracy with respect to the classical Bayesian filters and smoothers. We formulate the estimation problem as a dynamic generalized group Lasso problem and develop a class of smoothing-and-splitting methods to solve it. The Levenberg-Marquardt iterated extended Kalman smoother-based multiblock alternating direction method of multipliers (LM-IEKS-mADMMs) algorithms are based on the alternating direction method of multipliers (ADMMs) framework. This leads to minimization subproblems with an inherent structure to which three new augmented recursive smoothers are applied. Our methods can deal with large-scale problems without preprocessing for dimensionality reduction. Moreover, the methods allow one to solve nonsmooth nonconvex optimization problems. We then prove that under mild conditions, the proposed methods converge to a stationary point of the optimization problem. By simulated and real-data experiments, including multisensor range measurement problems, marine vessel tracking, autonomous vehicle tracking, and audio signal restoration, we show the practical effectiveness of the proposed methods
Three dimensional measurements of surface areas and burning velocities of turbulent spherical flames
No full textMeasurements of 3D turbulent flame surface area and burnt gas were carried out for spherically expanding flames in different methane-air and hydrogen-air mixtures using a high frequency swinging laser sheet technique based on Mie scattering. The corresponding turbulent burning velocities were measured simultaneously using the rate of pressure rise, at turbulence rms velocities between 0.3 and 2.0 m/s. The ratio of turbulent burning velocity enhancement utm/ul to flame surface area enhancement A3D/a3D was measured as a function of turbulence rms velocity. For the methane-air flames, the turbulent burning velocity enhancement is close to that of the flame surface area enhancement. For the hydrogen-air flames, the former can exceed the latter by a factor of up to 6 at the largest values of turbulence rms velocity tested. The large discrepancy suggests that in the case of hydrogen-air flames, the measured rate of burning per unit flame area is significantly enhanced by the turbulence. For the reconstructed A3D/a3D, the corresponding A2D/a2D are also discussed
Klinefelters Syndrome: Change in T-Scores with Testosterone, Bisphosphonate, and Vitamin D Treatment Over 6 Years
No full textBackground: Klinefelter’s syndrome (KS) is characterized by extra X chromosomes and features of primary hypogonadism including osteopenia and osteoporosis. Testosterone therapy (TTh) is widely used to treat men with KS and low serum testosterone/hypogonadal symptoms, though studies on its efficacy in improving bone density show varied outcomes. Materials and Methods: We studied the effects of TTh, bisphosphonates, and vitamin D/calcium in 38 men with KS and low testosterone, hypogonadal symptoms, and T-scores consistent with osteoporosis. Our aim was to investigate at the end of follow-up (median: 87 months, range: 27–147 months), associations between age, baseline total testosterone, and T-scores, and change in T-scores after treatment. Results: At final assessment, all men had T-score values outside the osteoporotic range (1.1 standard deviation [SD], 1.8 SD). Baseline age but not median baseline testosterone appeared associated with change in T-score and T-score at final assessment. All men had dual-energy X-ray absorptiometry every 6 months and demonstrated continued improvement in T-scores after 3 months and up to 72 months. Baseline age and T-scores (stratified by median) were associated with change in T-score at final assessment. Compared with men ‡51 years, those aged <51 years showed significantly greater improvement in T-scores between 6 and 30 months. Men with worse T-score values (<3.7 SD) showed significantly greater improvement at every time point up to 36 months. Our results indicate that TTh, bisphosphonates, and vitamin D/calcium improve osteoporosis although there is a need to better understand the effects of the individual therapies, age, and baseline T-score on treatment efficacy
Hospital-oriented quad-generation (HOQG)—A combined cooling, heating, power and gas (CCHPG) system
No full textAlong with the global spread of the COVID-19 pandemic, a number of hospitals are operating in the over-loaded state, which results in the ever-increasing requirements of cooling, heating, power, and medical gas supplies. This paper investigates a novel concept of hospital-oriented quad-generation (HOQG) to produce a combined cooling, heating, power and gas (CCHPG) system. Local renewable energy source (RES), high temperature superconducting (HTS) power cable and superconducting magnetic energy storage (SMES) device are used as the low-carbon electricity producer, carrier and regulator, respectively. Compared to the conventional copper cable and electrochemical battery, HTS terminal power units have superior advantages of high-efficiency power delivery and high-quality power compensation. To accommodate the surplus electricity from local RESs and guarantee emergency supply for the targeted hospital buildings, three cryogenic fluids of liquefied methane gas, liquefied oxygen and liquefied nitrogen are used as back-ups for both energy fuel and medical gas. By adopting a series of cascade energy utilization and thermally-activated energy conversion facilities, multiple clean energies of cooling, heating and power are produced to supply medical devices, and multiple medical gases of oxygen, nitrogen and carbon dioxide are delivered to hospitals for patient treatments. Compared to conventional diesel oil and compressed gas back-ups, these three cryogenic liquids have advantages of high-capacity, high-security storage and low-pollution utilization. Another possible benefit can be the low-temperature environment of these medical gases offers vaccines an appropriate delivering pathway against the COVID-19 pandemic. Therefore, the proposed HOQG can be expected to fulfill the demand of energy conservation and emission reduction simultaneously during the normal operation, as well as the demand of sustainable energy and medical gas supply under severe conditions such as natural and man-made disasters
Dual functionality of over-lithiated NMC for high energy silicon-based lithium-ion batteries
No full textOwing to their high specific capacity and suitably low operating potential, silicon-based anodes are an attractive alternative to graphite in next-generation lithium-ion batteries. However, silicon anodes suffer from low initial coulombic efficiency and fast capacity decay, limiting their widespread application. Pre-lithiation strategies are highly appealing to compensate for irreversible active lithium loss and to boost the cell energy density. In this work, we maximize the cell energy density by direct pre-lithiation of the NMC (LiNi0.5Mn0.3Co0.2O2) cathode to Li1+xNMCO2 without introducing inactive deadweight to either electrode. First, we demonstrate that Li1+xNMCO2 can be synthesized chemically, via reaction between NMC and lithium napthalide, and electrochemically. The NMC cathode is tolerant of a one-time over-lithiation up to 60 mA h gNMC-1, giving capacity retention on par with untreated NMC in half cell electrochemical cycling. Using synchrotron X-ray absorption spectroscopy (ex situ) and diffraction (in situ), we demonstrate that higher amounts of over-lithiation lead to local structure distortion-driven by transition metal reduction to Jahn-Teller active Mn3+ and Co2+-as well as bulk structural hysteresis during over-lithiation and layer "buckling"that increases the amount of lithium extracted from the structure in the charged state. The Li1+xNMCO2 with low-to-moderate over-lithiation capacity (23, 46, and 70 mA h gNMC-1) is proven to be a highly effective dual-purpose lithium source and cathode material in full cell tests with a commercially relevant Si-graphite anode. These cells show higher capacity, superior cycle life, and improved coulombic efficiencies when compared to those with stoichiometric NMC cathodes. This study introduces a new and simple method to pre-lithiate layered transition metal oxide cathodes, opening up new possibilities for the development of high energy density lithium-ion batteries with next-generation anodes. This journal i
Flotation of pipes and cables in consolidating backfill
No full textThis paper discusses the flotation of cables and pipelines that have been trenched using jet trenching during reconsolidation of the seabed soil. Utilising previously published data on the variation of clay strength with liquidity index, it is demonstrated for the first time that, while current industry guidance is appropriate for the low-plasticity clays for which much previous research has been carried out, it may be overly conservative for high-plasticity clays such as those found in the Gulf of Guinea or the Gulf of Mexico, owing to the differing strength and density characteristics of these soils
Fundamental Limits of Lossless Data Compression with Side Information
No full textThe problem of lossless data compression with side information available to both the encoder and the decoder is considered. The finite-blocklength fundamental limits of the best achievable performance are defined, in two different versions of the problem: Reference-based compression, when a single side information string is used repeatedly in compressing different source messages, and pair-based compression, where a different side information string is used for each source message. General achievability and converse theorems are established for arbitrary source-side information pairs. Nonasymptotic normal approximation expansions are proved for the optimal rate in both the reference-based and pair-based settings, for memoryless sources. These are stated in terms of explicit, finite-blocklength bounds, that are tight up to third-order terms. Extensions that go significantly beyond the class of memoryless sources are obtained. The relevant source dispersion is identified and its relationship with the conditional varentropy rate is established. Interestingly, the dispersion is different in reference-based and pair-based compression, and it is proved that the reference-based dispersion is in general smaller