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UCL University College London Eprints (400.673 recursos)

UCL Eprints collects the work of UCL researchers and makes it freely available over the web, helping the worldwide scholarly community to discover UCL research. Institutional repositories like UCL Eprints complement the traditional academic publishing and scholarly communications processes. They raise the visibility of research and help to maximise its impact. UCL researchers are encouraged to deposit a copy of each journal article, conference paper, working paper, and any other research output, in the UCL Eprints at the earliest opportunity, ensuring that their research reaches as wide an audience as possible.

Mostrando recursos 141 - 160 de 7.249

  1. 3D Modelling of Twist Wall at the Electrode Edge of Liquid Crystal Cells

    Day, SE; Nie, Z; Yang, M; Willman, E; Fernandez, FA
    Q-tensor simulation of the liquid crystal structure at the edge of electrodes has been carried out. The modeling shows a twist wall, which reverses direction to form a zig-zag structure. The results are compared with experiment. Also a defect loop is found in micro-lenses formed using a hole electrode structure.

  2. UCL-Lancet Commission on Migration and Health

    Abubakar, I; Devakumar, D; Madise, N; Sammonds, P; Groce, N; Zimmerman, C; Aldridge, RW; Clark, J; Horton, R
    Migration is a crucial issue for public health, with currently nearly a quarter of a billion international migrants and more than three times this number of migrants moving within their home country.1,2 Migration is not a new phenomenon, but international and internal migration seems to be increasing, triggered by displacement of large numbers of people in low-income and middle-income countries due to conflict, natural disasters, people's search for safety, and voluntary reasons such as economic opportunities.

  3. Variable structure observer for a class of nonlinear large-scale interconnected systems with uncertainties

    Mohamed, M; Yan, XG; Spurgeon, SK; Mao, Z
    In this paper, a variable structure observer design approach is proposed for a class of nonlinear, large-scale interconnected systems in the presence of unstructured uncertainty. The modern geometric approach is exploited to explore the system structure and a transformation is developed to facilitate observer design. Using the Lyapunov direct method, a robust asymptotic observer is presented which exploits the internal dynamic structure of the system as well as the structure of the uncertainties. The bounds on the uncertainties are nonlinear and are employed in the observer design to reject the effect of the uncertainties. A numerical example is presented to...

  4. Adaptive output feedback finite time control for a class of second order nonlinear systems

    Zhao, D; Spurgeon, SK; Yan, X
    This paper develops a finite time output feedback based control scheme for a class of nonlinear second order systems. The system representation includes both model uncertainty and uncertain parameters. A finite time parameter estimator is developed. This facilitates the design of a finite time observer based on the well- stablished step-by-step sliding mode observer design approach. A terminal sliding mode control scheme is then developed using the corresponding state estimates. The methodology is applied to a continuous stirred tank reactor system to validate the effectiveness of the proposed approach.

  5. How2Sketch: Generating Easy-To-Follow Tutorials for Sketching 3D Objects

    Hennessey, JW; Liu, H; Winnemöller, H; Dontcheva, M; Mitra, NJ
    Accurately drawing 3D objects is difficult for untrained individuals, as it requires an understanding of perspective and its effects on geometry and proportions. Step-by-step tutorials break the complex task of sketching an entire object down into easy-to-follow steps that even a novice can follow. However, creating such tutorials requires expert knowledge and is a time-consuming task. As a result, the availability of tutorials for a given object or viewpoint is limited. How2Sketch addresses this problem by automatically generating easy-to-follow tutorials for arbitrary 3D objects. Given a segmented 3D model and a camera viewpoint,it computes a sequence of steps for constructing...

  6. Threats to the validity of mutation-based test assessment

    Papadakis, M; Henard, C; Harman, M; Jia, Y; Traon, YL
    Much research on software testing and test techniques relies on experimental studies based on mutation testing. In this paper we reveal that such studies are vulnerable to a potential threat to validity, leading to possible Type I errors; incorrectly rejecting the Null Hypothesis. Our findings indicate that Type I errors occur, for arbitrary experiments that fail to take countermeasures, approximately 62% of the time. Clearly, a Type I error would potentially compromise any scientific conclusion. We show that the problem derives from such studies’ combined use of both subsuming and subsumed mutants. We collected articles published in the last two...

  7. Sapienz: Multi-objective automated testing for android applications

    Mao, K; Harman, M; Jia, Y
    We introduce Sapienz, an approach to Android testing that uses multi-objective search-based testing to automatically explore and optimise test sequences, minimising length, while simultaneously maximising coverage and fault revelation. Sapienz combines random fuzzing, systematic and search-based exploration, exploiting seeding and multi-level instrumentation. Sapienz significantly outperforms (with large effect size) both the state-of-the-art technique Dynodroid and the widely-used tool, Android Monkey, in 7/10 experiments for coverage, 7/10 for fault detection and 10/10 for fault-revealing sequence length. When applied to the top 1, 000 Google Play apps, Sapienz found 558 unique, previously unknown crashes. So far we have managed to make contact...

  8. Inference of tissue haemoglobin concentration from Stereo RGB

    Jones, G; Clancy, NT; Arridge, S; Elson, DS; Stoyanov, D
    Multispectral imaging (MSI) can provide information about tissue oxygenation, perfusion and potentially function during surgery. In this paper we present a novel, near real-time technique for intrinsic measurements of total haemoglobin (THb) and blood oxygenation (SO 22 ) in tissue using only RGB images from a stereo laparoscope. The high degree of spectral overlap between channels makes inference of haemoglobin concentration challenging, non-linear and under constrained. We decompose the problem into two constrained linear sub-problems and show that with Tikhonov regularisation the estimation significantly improves, giving robust estimation of the THb. We demonstrate by using the co-registered stereo image data...

  9. Long-finned pilot whale population diversity and structure in Atlantic waters assessed through biogeochemical and genetic markers

    Monteiro, SS; Mendez-Fernandez, P; Piertney, S; Moffat, CF; Ferreira, M; Vingada, JV; Lopez, A; Brownlow, A; Jepson, P; Mikkelsen, B; Niemeyer, M; Carvalho, JC; Pierce, GJ
    Integration of ecological and genetic approaches is a particularly powerful strategy to identify natural population diversity and structure over different timescales. To investigate the potential occurrence of population differentiation in long-finned pilot whales Globicephala melas in the North Atlantic, both biogeochemical (fatty acids and stable isotopes) and genetic (mitochondrial DNA) markers were analyzed in animals from 4 regions within the North Atlantic: the northwestern Iberian Peninsula, the United Kingdom, the Faroe Islands and the United States of America. Genetic data revealed strong regional levels of divergence, although analysis of molecular variance revealed no differentiation between the northeastern and northwestern Atlantic....

  10. In vivo T₁ mapping of the spinal cord using a reduced Field-of-View Inversion Recovery sequence (IR-ZOOM-EPI)

    Battiston, M; Schneider, T; Wheeler-Kingshott, CAA; Samson, RS
    The T1 relaxation time is a fundamental quantitative Magnetic Resonance parameter widely used to characterize healthy and pathological tissue. However, investigation of quantitative T1 in the human spinal cord has been limited to date. In this work, we propose a scan time efficient protocol in the spinal cord for Inversion Recovery T1 mapping, which is considered the “gold-standard” method. The mean (± standard deviation) T1 for white matter and grey matter in the cervical spinal cord were found to be respectively 1096 (±26) ms and 1153 (±24) ms.

  11. In vivo quantitative Magnetisation Transfer in the cervical spinal cord using reduced Field-of-View imaging: a feasibility study

    Battiston, M; Grussu, F; Fairney, J; Prados, F; Ourselin, S; Cercignani, M; Wheeler-Kingshott, CAA; Samson, R
    Quantitative Magnetization Transfer (qMT) Imaging techniques offer the possibility to estimate tissue macromolecular fraction, which has been shown to be specific for myelin in the brain and spinal cord. To date, applications of qMT in the spinal cord have been hampered by prohibitive protocol duration. We propose a novel approach for qMT in the spinal cord based on the combination of offresonance saturation a small field-of-view imaging, with the potential of reducing scan time needed to perform qMT in the spinal cord.

  12. Development of Pediatric covered stent using nanocomposite material

    Farhatnia, Y; Tan, A; G, N; Rahmani, B; Burriesci, G; Tsui, J

  13. Referrals to a facial pain service

    Lang, M; Selvadurai, T; Zakrzewska, JM
    AIM: To assess the quality of referral letters to a facial pain service and highlight the key requirements of such letters. METHOD: The source of all referral letters to the service for five years was established. For one year the information provided in 94 referrals was assessed. Using a predetermined checklist of essential information the referral letters were compared to these set criteria. RESULTS: The service received 7,001 referrals and, on average, general dental practitioners (GDPs) referred 303 more patients per year than general medical practitioners (GMPs). Seventy-one percent of all referrals were from primary care practitioners, the rest were from specialists....

  14. Heavy drinking days and mental health: an exploration of the dynamic 10-year longitudinal relationship in a prospective cohort of untreated heavy drinkers

    Bell, S; Orford, J; Britton, A
    Identifying dominant processes that underlie the development of other processes is important when evaluating the temporal sequence between disorders. Such information not only improves our understanding of etiology but also allows for effective intervention strategies to be tailored. The temporal relationship between alcohol intake and mental health remains poorly understood, particularly in nonclinical samples. The purpose of this study was to disentangle the dominant temporal sequence between mental health and frequency of heavy drinking days.

  15. Autoimmune Encephalitis

    Zandi, MS

  16. Development of a microbioreactor cassette for synthetic biology applications

    Barrientos, N; Davies, MJ; Marques, MPC; Nesbeth, DN; Szita, N; Lye, GJ

  17. Impaired awareness of motor intention in functional neurological disorder: implications for voluntary and functional movement

    Baek, K; Doñamayor, N; Morris, LS; Strelchuk, D; Mitchell, S; Mikheenko, Y; Yeoh, SY; Phillips, W; Zandi, M; Jenaway, A; Walsh, C; Voon, V
    Copyright © Cambridge University Press 2017 This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.Background: Functional neurological disorders (FNDs), also known as conversion disorder, are unexplained neurological symptoms unrelated to a neurological cause. The disorder is common, yet poorly understood. The symptoms are experienced as involuntary but have similarities to voluntary processes. Here we studied intention awareness in FND. Method: A total of 26 FND patients and 25 healthy volunteers participated in this functional magnetic...

  18. Notes on the kidney and its diseases for the neurologist

    Zandi, MS; Coles, AJ

  19. Limbic encephalitis associated with antibodies to the NMDA receptor in Hodgkin lymphoma

    Zandi, MS; Irani, SR; Follows, G; Moody, AM; Molyneux, P; Vincent, A

  20. N-methyl-D-aspartate antibody encephalitis: temporal progression of clinical and paraclinical observations in a predominantly non-paraneoplastic disorder of both sexes

    Irani, SR; Bera, K; Waters, P; Zuliani, L; Maxwell, S; Zandi, MS; Friese, MA; Galea, I; Kullmann, DM; Beeson, D; Lang, B; Bien, CG; Vincent, A

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