Now showing items 21-40 of 654

    • Adaptive bees algorithm : bioinspiration from honeybee foraging to optimize fuel economy of a semi-track air-cushion vehicle

      Xu, Shuo; Yu, Fan; Luo, Zhe; Ji, Ze; Pham, Duc Truong; Qiu, Renxi; Shanghai Jiao Tong University; Cardiff University (Oxford University Press, 2011-01-04)
      This interdisciplinary study covers bionics, optimization and vehicle engineering. Semi-track air-cushion vehicle (STACV) provides a solution to transportation on soft terrain, whereas it also brings a new problem of excessive fuel consumption. By mimicking the foraging behaviour of honeybees, the bioinspired adaptive bees algorithm (ABA) is proposed to calculate its running parameters for fuel economy optimization. Inherited from the basic algorithm prototype, it involves parallel-operated global search and local search, which undertake exploration and exploitation, respectively. The innovation of this improved algorithm lies in the adaptive adjustment mechanism of the range of local search (called ‘patch size’) according to the source and the rate of change of the current optimum. Three gradually in-depth experiments are implemented for 143 kinds of soils. First, the two optimal STACV running parameters present the same increasing or decreasing trend with soil parameters. This result is consistent with the terramechanics-based theoretical analysis. Second, the comparisons with four alternative algorithms exhibit the ABA's effectiveness and efficiency, and accordingly highlight the advantage of the novel adaptive patch size adjustment mechanism. Third, the impacts of two selected optimizer parameters to optimization accuracy and efficiency are investigated and their recommended values are thus proposed.
    • 3D-holoscopic imaging: a new dimension to enhance Iimaging in minimally invasive therapy in urologic oncology

      Makanjuola, Jonathan K.; Aggoun, Amar; Swash, Mohammad; Grange, Philippe C.R.; Challacombe, Benjamin; Dasgupta, Prokar; Guy's and St Thomas' Hospital; Brunel University; King's College Hospital (Mary Ann Liebert, 2013-05)
      Background and Purpose: Existing imaging modalities of urologic pathology are limited by three-dimensional (3D) representation on a two-dimensional screen. We present 3D-holoscopic imaging as a novel method of representing Digital Imaging and Communications in Medicine data images taken from CT and MRI to produce 3D-holographic representations of anatomy without special eyewear in natural light. 3D-holoscopic technology produces images that are true optical models. This technology is based on physical principles with duplication of light fields. The 3D content is captured in real time with the content viewed by multiple viewers independently of their position, without 3D eyewear. Methods: We display 3D-holoscopic anatomy relevant to minimally invasive urologic surgery without the need for 3D eyewear. Results: The results have demonstrated that medical 3D-holoscopic content can be displayed on commercially available multiview auto-stereoscopic display. Conclusion: The next step is validation studies comparing 3D-Holoscopic imaging with conventional imaging.
    • Disparity map compression for depth-image-based rendering

      Cheung, Gene; Ortega, Antonio; Kim, Woo-Shik; Velisavljević, Vladan; Kubota, Akira; National Institute of Informatics, Japan; University of Southern California; Texas Instruments; University of Bedfordshire; Chuo University (Springer, 2012-03)
    • Joint source and channel coding of view and rate scalable multi-view video

      Chakareski, Jacob; Velisavljević, Vladan; Stankovic, Vladimir; University of Alabama; University of Bedfordshire; Strathclyde University (IEEE, 2014-10)
      We study multicast of multi-view content in the video plus depth format to heterogeneous clients. We design a joint source-channel coding scheme based on view and rate embedded source coding and rateless channel coding. It comprises an optimization framework for joint view selection and source-channel rate allocation, and includes a fast method for separate optimization of the source and channel coding components, at a negligible performance loss wrt the joint solution. We demonstrate performance gains over a state-of-the-art method based on H.264/SVC, in the case of two client classes.
    • Scalable user-adaptive multiview video coder

      Velisavljević, Vladan; Chakareski, Jacob; Stankovic, Vladimir; University of Bedfordshire; University of Alabama; Strathclyde University (IEEE, 2013-07)
      We derive an optimization framework for joint view and rate scalable coding of multi-view video content represented in the texture plus depth format. The optimization enables the sender to select the subset of coded views and their encoding rates such that the aggregate distortion over a continuum of synthesized views is minimized. We construct the view-rate scalable bitstream such that it delivers optimal performance simultaneously over a discrete set of transmission rates. In conjunction, we develop a user interaction model that characterizes the view selection actions of the client as a Markov chain over a discrete state-space. Our scheme outperforms the state-of-the-art H.264 SVC codec as well as a multi-view wavelet-based coder equipped with a uniform rate allocation strategy, across all scenarios studied. Finally, we observed that the interactivity-aware coding delivers superior performance over conventional allocation techniques that do not anticipate the client's view selection actions in their operation.
    • Performance analysis of energy detection over hyper-Rayleigh fading channels

      Chatziantoniou, Eleftherios; Allen, Ben; Velisavljević, Vladan; University of Bedfordshire (IET, 2015-01-01)
      This study investigates the performance of energy detection (ED)-based spectrum sensing over two-wave with diffused power (TWDP) fading channels, which have been found to provide accurate characterisation for a variety of fading conditions. A closed-form expression for the average detection probability of ED-based spectrum sensing over TWDP fading channels is derived. This expression is then used to describe the behaviour of ED-based spectrum sensing for a variety of channels that include Rayleigh, Rician and hyper-Rayleigh fading models. Such fading scenarios present a reliable behavioural model of machine-to-machine wireless nodes operating in confined structures such as in-vehicular environments.
    • View-popularity-driven joint source and channel coding of view and rate scalable multi-view video

      Chakareski, Jacob; Velisavljević, Vladan; Stankovic, Vladimir; University of Alabama; University of Bedfordshire; Strathclyde University (IEEE, 2015-02-11)
      We study the scenario of multicasting multi-view video content, recorded in the video plus depth format, to a collection of heterogeneous clients featuring Internet access links of diverse packet loss and transmission bandwidth values. We design a popularity-aware joint source-channel coding optimization framework that allocates source and channel coding rates to the captured content, such that the aggregate video quality of the reconstructed content across the client population is maximized, for the given packet loss and bandwidth characteristics of the clients and their view selection preferences. The source coding component of our framework features a procedure for generating a view and rate embedded bitstream that is optimally decodable at multiple data rates and accounts for the different popularity of diverse video perspectives of the scene of interest, among the clients. The channel coding component of our framework comprises an expanding-window rateless coding procedure that optimally allocates parity protection bits to the source encoded layers, in order to address packet loss across the unreliable client access links. We develop an optimization method that jointly computes the source and channel coding decisions of our framework, and also design a fast local-search-based solution that exhibits a negligible performance loss relative to the full optimization. We carry out comprehensive simulation experiments and demonstrate significant performance gains over competitive state-of-the-art methods (based on H.264/AVC and network coding, and H.264/SVC and our own channel coding procedure), across different scenario settings and parameter values.
    • Threshold optimization for energy detection-based spectrum sensing over hyper-Rayleigh fading channels

      Chatziantoniou, Eleftherios; Allen, Ben; Velisavljević, Vladan; University of Bedfordshire (IEEE, 2015-06)
    • Introduction to the issue on visual signal processing for wireless networks

      Velisavljević, Vladan; Pesquet-Popescu, Beatrice; Vucetic, Branka; Reibman, Amy R.; Yang, Chenyang; University of Bedfordshire; ParisTech Telecom; University of Sydney; Purdue University; Beihang University (IEEE, 2015-02)
    • An empirical polarisation domain channel availability model for cognitive radio

      Chatziantoniou, Eleftherios; Allen, Ben; Velisavljević, Vladan; University of Bedfordshire (IEEE, 2014-09)
      In dynamic spectrum access networks, cognitive radio terminals monitor their spectral environment in order to detect and opportunistically access unoccupied frequency channels. The overall performance of such networks depends on the spectrum occupancy or availability patterns. Accurate knowledge on the channel availability enables optimum performance of such networks in terms of spectrum and energy efficiency. This work proposes a novel probabilistic channel availability model that can describe the channel availability in different polarizations for mobile cognitive radio terminals that are likely to change their orientation during their operation. A Gaussian approximation is used to model the empirical occupancy data that was obtained through a measurement campaign in the cellular frequency bands within a realistic operational scenario.
    • Centralized and interactive compression of multiview images

      Gelman, Andriy; Dragotti, Pier Luigi; Velisavljević, Vladan; Imperial College London; Deutsche Telekom Laboratories (SPIE, 2011-09-08)
    • The refocusing distance of a standard plenoptic photograph

      Hahne, Christopher; Aggoun, Amar; Velisavljević, Vladan; University of Bedfordshire (IEEE, 2015-06-12)
      In the past years, the plenoptic camera aroused an increasing interest in the field of computer vision. Its capability of capturing three-dimensional image data is achieved by an array of micro lenses placed in front of a traditional image sensor. The acquired light field data allows for the reconstruction of photographs focused at different depths. Given the plenoptic camera parameters, the metric distance of refocused objects may be retrieved with the aid of geometric ray tracing. Until now there was a lack of experimental results using real image data to prove this conceptual solution. With this paper, the very first experimental work is presented on the basis of a new ray tracing model approach, which considers more accurate micro image centre positions. To evaluate the developed method, the blur metric of objects in a refocused image stack is measured and compared with proposed predictions. The results suggest quite an accurate approximation for distant objects and deviations for objects closer to the camera device.
    • Healthcare-event driven semantic knowledge extraction with hybrid data repository

      Yu, Hong Qing; Zhao, Xia; Zhen, Xin; Dong, Feng; Liu, Enjie; Clapworthy, Gordon J.; University of Bedfordshire (IEEE, 2014-08)
      In this paper, we introduce a Healthcare-Event (H-event) based knowledge extraction approach on a hybrid data repository. The repository collects (with individual user's permission) dynamic and large volume healthcare related data from various resources such as wearable sensors, social media Web APIs and our application itself. The proposed extraction approach relies on two data processing processes. One is the data integration process to dynamically retrieving the large data using public data service APIs. The first process also generates a set of big knowledge bases and stored in NoSQL storage. This paper will focus on the second extraction process that is the H-Event based ontological knowledge extraction for detecting and monitoring user's healthcare related situations, such as medical symptoms, treatments, conditions and daily activities from the NoSQL knowledge bases. The second process can be seen as post-processing step to detect more explicit healthcare knowledge about personalised health conditions and represent the knowledge using RDF formats in a semantic triple repository to enhance further data analytics.
    • Support for the calculation of stent fatigue fracture in peripheral arteries

      McFarlane, Nigel J.B.; Wei, Hui; Zhao, Youbing; Clapworthy, Gordon J.; Testi, Debora; Chiarini, Alessandro; University of Bedfordshire (European Association for Computer Graphics, 2013)
      Vascular stenting is a medical intervention in which a wire mesh tube is inserted into an artery or vein to provide internal support. This is a safe and common procedure, but stents are now increasingly being deployed in peripheral locations, such as the femoral artery, as part of a procedure called Peripheral Vascular Angioplasty (PVA). Stents in such locations are subject to cyclic bending, and are therefore at risk of fatigue fracture. This paper describes the work of the RT3S project, which brings together stent modelling, surgical simulation and risk calculation for surgical planning. This will allow the clinical user to interactively assess different stent models and deployment options for breakage risk. In the RT3S system, models of several commercial models of self-expanding stent are available for simulation. The placement of the stent in the vessel and the withdrawal of the catheter sheath to expand the stent are visualised. A simplex control mesh is used to guide the deformation of the stent from its compressed start configuration to its expanded final position. The fracture risk for the given model and its patient-specific final position is precomputed using the response surfaces methodology.
    • A cross-platform approach to the treatment of ambylopia

      Wei, Hui; Zhao, Youbing; Dong, Feng; Saleh, George; Ye, Xujiong; Clapworthy, Gordon J.; University of Bedfordshire (IEEE, 2013-11)
      In this paper, we introduce a diagnosis and treatment for amblyopia performed through a game suitable for children aged between 3 and 7. Our method places emphasis on cooperation between the two eyes to achieve a good binocular outcome to aid the recovery of depth perception. Our approach is not limited to a particular device or platform nor even to a particular form of game. Several prototype games have been developed, including 2D games and 3D games.
    • Pre-surgery planning in vascular procedures: an introduction to the RT3S project

      Dubini, Gabriele; Guarneri, Maria Renata; Clapworthy, Gordon J.; Katsaounis, Nassos; Lawford, Patricia; Petrakis, Euripides; Rochette, Michel; Silvestro, Claudio; Testi, Debora; Politec. di Milano; et al. (IEEE, 2013-11)
      RT3S is an EU-funded project in an area of e-health - ICT for Patient Safety. Specifically, RT3S is developing a patient-centred, probabilistic model for peripheral stent fatigue-fracture, integrated within a real-time, computer-aided surgery planning application. RT3S will provide advice on fracture risk for individual combinations of patient anatomy and stent design. Alongside the pre-operational software tool, which is addressed mainly to interventional radiologists, RT3S has also developed a training application that will be of benefit to trainee vascular interventionists and engineers in medical device companies. This paper provides an overview of the work performed during nearly three years of project activities and also addresses the motivation leading to RT3S and the expected impact.
    • WebGL-based interactive rendering of whole body anatomy for web-oriented visualisation of avatar-centered digital health data

      Zhao, Youbing; Zhao, X.; Dong, Feng; Clapworthy, Gordon J.; Ersotelos, Nikolaos; Liu, Enjie; University of Bedfordshire (IEEE, 2013-11)
      The visualisation of whole-body anatomy has a variety of applications in health-related analysis and simulation. However, the rendering of complex 3D human anatomy models is generally performed by standalone applications rather than via a web interface, as rendering large 3D models has always been a weak spot of traditional web browsers. Consequently, online access to, and exploration of, the human anatomy in 3D has not been feasible in the past. With the advent of WebGL and HTML5, high performance OpenGL rendering seamlessly integrated with the web interface is now within reach, and this opens the possibility of visualising avatar-centered health data via a web interface. In this paper, a WebGL-based prototype for rendering whole-body anatomy is introduced, and the technical details are presented.
    • Dynamic PCI assignment in two-tier networks based on cell activity prediction

      Zhang, J.; Zhang, X.; Xiao, Z.; Liu, Enjie; University of Bedfordshire; Hunan University; University of Sheffield (IET, 2013-11)
      Physical cell identity (PCI) is used to identify each cell. However, with the introduction of femtocells, 8 bytes allocation for PCI cannot accommodate a large number of femtocells. The current solution in 3GPP Release 9 is to use cell global identity associated with PCI to resolve this problem. However, this solution may incur higher inbound handover failure. A dynamic PCI assignment based on cell activity level prediction is proposed. The system level simulation showed that the approach outperforms the existing approaches.
    • Enhancing Bayesian estimators for removing camera shake

      Wang, Chao; Yue, Y.; Dong, Feng; Tao, Yubo; Ma, Xiangyin; Clapworthy, Gordon J.; Ye, Xujiong; University of Bedfordshire (Wiley, 2013)
      The aim of removing camera shake is to estimate a sharp version x from a shaken image y when the blur kernel k is unknown. Recent research on this topic evolved through two paradigms called MAP(k) and MAP(x,k). MAP(k) only solves for k by marginalizing the image prior, while MAP(x,k) recovers both x and k by selecting the mode of the posterior distribution. This paper first systematically analyses the latent limitations of these two estimators through Bayesian analysis. We explain the reason why it is so difficult for image statistics to solve the previously reported MAP(x,k) failure. Then we show that the leading MAP(x,k) methods, which depend on efficient prediction of large step edges, are not robust to natural images due to the diversity of edges. MAP(k), although much more robust to diverse edges, is constrained by two factors: the prior variation over different images, and the ratio between image size and kernel size. To overcome these limitations, we introduce an inter-scale prior prediction scheme and a principled mechanism for integrating the sharpening filter into MAP(k). Both qualitative results and extensive quantitative comparisons demonstrate that our algorithm outperforms state-of-the-art methods.
    • A user interface design for a patient oriented digital patient

      Ersotelos, Nikolaos; Zhao, Xia; Zhao, Youbing; Wei, Hui; Liu, Enjie; Clapworthy, Gordon J.; Dong, Feng; University of Bedfordshire (IEEE, 2013-11)
      MyHealthAvatar is designed to provide a digital representation of patient health status. It aims to become a `lifetime companion' for individual citizens that will facilitate the collection of, and access to, long term health-status information. This avatar is not only extremely valuable for clinical decision-making, but it will generate data to support clinical investigation, thereby leading to strengthened multidisciplinary research and excellence in supporting innovative medical care across the population. My Health Avatar platform is currently under development. The purpose of this paper is to present the scope, the provided service and the future plans of the platform as well as a detailed description of the visual representation of the MyHealthAvatar platform.