MRC Laboratory of Molecular Biology
CUED - Cambridge University Engineering DepartmentNot a member yet
45551 research outputs found
Sort by
Optimal PMU placement approach for power systems considering non-Gaussian measurement noise statistics
No full textThis paper investigates how to add a limited number of Phasor Measurement Units (PMUs) to the existing monitoring system so as to improve the estimation accuracy further. The existing methods are usually based on Gaussian noise assumption and the weighted least squares (WLS) estimator is taken into account. However, the Gaussian noise assumption is not always true in reality and the WLS is non-robust in this case. This paper proposes a new optimal PMU placement approach where the distribution of measurement noise can be non-Gaussian or Gaussian and many robust estimators such as the maximum likelihood estimator, Multiple-Segment, Quadratic-Linear, Square-Root and Schweppe-Huber Generalized-M estimator are considered. Based on the new Gain matrix obtained from the influence function approximation, the D-optimal and E-optimal experiment criterions are exploited in the optimal PMU placement problem. A convex relaxation in conjunction with an optimization improvement method based on the Fedorov exchange algorithm is utilized to solve the optimizing problem. Simulations on the IEEE 57-bus system and the Polish 2383-bus system are carried out to evaluate the effective performance of the proposed approach
The use of high decomposition temperature materials for chemical looping electricity storage
No full textUsing chemical looping as a large-scale electricity storage mechanism, where electricity is converted and stored as chemical energy via a thermochemical reaction, is an attractive concept. It can achieve high volumetric capacity and moderate round-trip efficiency. In early schemes, a heat pump was employed to convert electricity to heat, but its operating temperature is limited and only those solid oxides capable of releasing oxygen at low temperatures (below 900 K) were feasible. Therefore, ways of using materials with a higher decomposition temperature, i.e. the commonly used materials in chemical looping systems, are investigated. Two methods are proposed: using a vacuum pump to reduce the charging pressure or an electrical heater to increase the charging temperature. Results show using a vacuum pump to be infeasible, whereas, a simplified charging cycle only comprising of an electrical heater and a recuperator is deemed optimal. This system capacity can be as high as 600–800 kWh/m3 with round-trip efficiency in the range of 40–55%
High-yield parallel fabrication of quantum-dot monolayer single-electron devices displaying Coulomb staircase, contacted by graphene
No full textIt is challenging for conventional top-down lithography to fabricate reproducible devices very close to atomic dimensions, whereas identical molecules and very similar nanoparticles can be made bottom-up in large quantities, and can be self-assembled on surfaces. The challenge is to fabricate electrical contacts to many such small objects at the same time, so that nanocrystals and molecules can be incorporated into conventional integrated circuits. Here, we report a scalable method for contacting a self-assembled monolayer of nanoparticles with a single layer of graphene. This produces single-electron effects, in the form of a Coulomb staircase, with a yield of 87 ± 13% in device areas ranging from < 800 nm2 to 16 μm2, containing up to 650,000 nanoparticles. Our technique offers scalable assembly of ultra-high densities of functional particles or molecules that could be used in electronic integrated circuits, as memories, switches, sensors or thermoelectric generators
SelfHAR: Improving Human Activity Recognition through Self-training with Unlabeled Data.
No full textChondroitin 6-sulphate is required for neuroplasticity and memory in ageing
No full textPerineuronal nets (PNNs) are chondroitin sulphate proteoglycan-containing structures on the neuronal surface that have been implicated in the control of neuroplasticity and memory. Age-related reduction of chondroitin 6-sulphates (C6S) leads to PNNs becoming more inhibitory. Here, we investigated whether manipulation of the chondroitin sulphate (CS) composition of the PNNs could restore neuroplasticity and alleviate memory deficits in aged mice. We first confirmed that aged mice (20-months) showed memory and plasticity deficits. They were able to retain or regain their cognitive ability when CSs were digested or PNNs were attenuated. We then explored the role of C6S in memory and neuroplasticity. Transgenic deletion of chondroitin 6-sulfotransferase (chst3) led to a reduction of permissive C6S, simulating aged brains. These animals showed very early memory loss at 11 weeks old. Importantly, restoring C6S levels in aged animals rescued the memory deficits and restored cortical long-term potentiation, suggesting a strategy to improve age-related memory impairment
Robust Multisensor MeMBer Filter for Multiple Extended-Target Tracking
No full textThis paper develops a robust extended-target multisensor multitarget multi-Bernoulli (ET-MS-MeMBer) filter for enhancing the unsatisfactory quality of measurement partitions arising in the classical ET-MS-MeMBer filter due to increased clutter intensities. Specifically, the proposed method considers the influence of the clutter measurement set by introducing the ratio of the target likelihood to the clutter likelihood. With the constraint of the clutter measurement set, it can obtain better multisensor measurement partitioning results under the original two-step greedy partitioning mechanism. Subsequently, the single-target multisensor likelihood function for the clutter case is derived. Simulation results reveal a favorable comparison to the ET-MS-MeMBer filter in terms of accuracy in estimating the target cardinality and target state under conditions with increased clutter intensities
Enabling In-Ear Magnetic Sensing: Automatic and User Transparent Magnetometer Calibration
No full textEarables (in-ear wearables) are a new frontier in wearables. Acting both as leisure devices, providing personal audio, as well as sensing platforms, earables could collect sensor data for the upper part of the body, subject to fewer vibrations and random movement variations than the lower parts of the body, due to inherent damping in the musculoskeletal system. These data may enable application domains such as augmented/virtual reality, medical rehabilitation, and health condition screening. Unfortunately, earables have inherent size, shape, and weight constraints limiting the type and position of the sensors on such platforms. For instance, lacking a magnetometer in all earables reference platforms, earables lack reference points. Thus, it becomes harder to work with absolute orientations. Embedding magnetometers in earables is challenging, as these rely heavily on radio (mostly Bluetooth) communication (RF) and contain magnets for magnetic-driven speakers and docking. We explore the feasibility of adding a built-in magnetometer in an earbud, presenting the first comprehensive study of the magnetic interference impacting the magnetometer when placed in an earable: both that caused by the speaker and by RF (music streaming and voice calls) are considered. We find that appropriate calibration of the magnetometer removes the offsets induced by the magnets, the speaker, and the variable interference due to BT. Further, we present an automatic, user-transparent adaptive calibration that obviates the need for alternative, expensive, and error-prone manual, or robotics, calibration procedures. Our evaluation shows how our calibration approach performs under different conditions, achieving convincing results with errors below 3° for the majority of the experiments
Modelling the Frequency Dependence of the Open-Circuit Voltage of a High-T<inf>c</inf>Superconducting Dynamo
No full textA high-Tc superconducting (HTS) dynamo enables the injection of large DC currents into a superconducting circuit, without the requirement for current leads. In this work, we attempt to explain the frequency dependence of such dynamos/flux pumps reported in the literature, where it is observed that the rate at which the open-circuit DC voltage increases reduces with increasing frequency, in contrast to the expected linear behaviour. Heat generated in the HTS wire has been the common explanation given to date for this phenomenon. Here we offer an alternative explanation: the interaction between and current flow in the different layers of the HTS wire as the frequency of the dynamo increases. Our claim is based on numerical analysis using a segregated H-formulation finite-element model of the HTS dynamo benchmark problem that is extended to include the full HTS wire architecture and coupled with a thermal model. This framework enables us to efficiently model the relative movement between the rotating roomerature permanent magnet and the stationary HTS wire and to study the impact of the frequency of rotation and temperature on the open-circuit DC voltage of the dynamo
An experimental investigation to model wheezing in lungs
No full textA quarter of the world's population experience wheezing. These sounds have been used for diagnosis since the time of the Ebers Papyrus (ca 1500 BC). We know that wheezing is a result of the oscillations of the airways that make up the lung. However, the physical mechanisms for the onset of wheezing remain poorly understood, and we do not have a quantitative model to predict when wheezing occurs. We address these issues in this paper. We model the airways of the lungs by a modified Starling resistor in which airflow is driven through thin, stretched elastic tubes. By completing systematic experiments, we find a generalized 'tube law' that describes how the cross-sectional area of the tubes change in response to the transmural pressure difference across them. We find the necessary conditions for the onset of oscillations that represent wheezing and propose a flutter-like instability model for it about a heavily deformed state of the tube. Our findings allow for a predictive tool for wheezing in lungs, which could lead to better diagnosis and treatment of lung diseases
Application of microbially induced carbonate precipitation to form bio-cemented artificial sandstone
No full textIt is difficult to collect and characterise well-preserved samples of weakly-cemented granular rocks as conventional sampling techniques often result in destruction of the cementation. An alternative approach is to prepare synthetic geomaterials to match required specifications. This paper introduces microbially induced carbonate precipitation (MICP) as a method to reliably deliver artificially cemented specimens with customised properties, closely resembling those of soft carbonate sandstones. The specimens are generated from materials with two highly different particle size distributions (PSDs) to access a range of achievable combinations of strengths and porosities. The MICP parameters are kept constant across all samples to obtain similar calcium carbonate characteristics (size of individual crystals, type, etc.), while injected volume is varied to achieve different cementation levels. Although uniform cementation of very coarse sands has been considered very difficult to achieve, the results show that both the fine and coarse sand specimens present high degrees of uniformity and a good degree of repeatability. The unconfined compressive strengths (UCSs) (less than 3000 kPa) and porosities (0.25–0.4) of the artificial specimens fall in the same range of values reported for natural rocks. The strength gain was greater in the fine sand than that in the coarse sand, as the void size in the latter was significantly larger compared to the calcium carbonate crystals’ size, resulting in precipitation on less effective locations, away from contacts between particles. The strengths and porosities obtained for the two sands in this work fall within ranges reported in the literature for natural soft rocks, demonstrating the MICP technique is able to achieve realistic properties and may be used to produce a full range of properties by varying the grain sizes, and possibly the width of PSD